Written emotional disclosure for asthma
Abstract
Background
Psychological stress has been widely implicated in asthma exacerbation. Evidence suggests that written emotional disclosure, an intervention that involves writing about traumatic or stressful experiences, helps to reduce stress and promote physical and psychological well‐being. Written emotional disclosure may have a role in the management of asthma.
Objectives
This review aims to determine the effectiveness of written emotional disclosure for people with asthma, specifically, to assess:
1. overall efficacy of emotional disclosure compared with emotionally neutral writing on self reported quality of life in people with asthma;
2. overall efficacy of emotional disclosure compared with emotionally neutral writing on objective measures of health outcome in people with asthma; and
3. comparative efficacy of different types of emotional disclosure for people with asthma.
Search methods
Trials were identified from the Cochrane Airways Group Specialised Register of trials, CENTRAL, MEDLINE, EMBASE, CINAHL, AMED and PsycINFO. The latest search was conducted in January 2014.
Selection criteria
Randomised controlled trials published in any language comparing written emotional disclosure intervention versus a control writing (emotionally neutral) intervention in participants with asthma were included in the review.
Data collection and analysis
Two review authors independently assessed studies against predetermined inclusion criteria and extracted the data. Corresponding authors were contacted when necessary to provide additional information.
Main results
Four studies, involving a total of 414 participants, met the inclusion criteria. Three studies were conducted in adult participants and one in adolescents. The average age of participants ranged from 14 to 43 years. The trials lasted between two months and 12 months. The interventions were based on Pennebaker's method. The risk of bias across most domains of the studies was generally considered to be low, however three of four studies were considered at high risk of bias due to lack of assessor blinding and one study was at high risk of bias for selective reporting. The interpretation of these studies was limited by diverse outcome measurements, measurement tools, control group techniques, and number and/or times of follow‐up. A pooled result from the four studies, including a total of 146 intervention and 135 control participants, indicated uncertain effect in forced expiratory volume in one second (FEV1) % predicted between the disclosure group and the control group (mean difference (MD) 3.43%, 95% confidence interval (CI) ‐0.61% to 7.47%; very low‐quality evidence) at ≤ three months' follow‐up. Similarly, evidence from two studies indicated that written emotional disclosure found uncertain effect on forced vital capacity (FVC) (standardised mean difference (SMD) ‐0.02, 95% CI ‐0.30 to 0.26; low‐quality evidence) and asthma symptoms (SMD ‐0.22, 95% CI ‐0.52 to 0.09; low‐quality evidence) but may result in improved asthma control at ≤ three months' follow‐up (SMD 0.29, 95% CI 0.01 to 0.58; low‐quality evidence). We were unable to pool the data for other outcomes. Results from individual trials did not reveal a significant benefit of written emotional disclosure for quality of life, medication use, healthcare utilisation or psychological well‐being. Evidence from one trial suggests a significant reduction in beta agonist use (MD ‐1.62, 95% CI ‐2.62 to ‐0.62; low‐quality evidence) at ≤ three months' follow‐up in the disclosure group compared with controls. The review did not address any adverse effects of emotional writing.
Authors' conclusions
Evidence was insufficient to show whether written emotional disclosure compared with writing about non‐emotional topics had an effect on the outcomes included in this review. Evidence is insufficient to allow any conclusions as to the role of disclosure in quality of life, psychological well‐being, medication use and healthcare utilisation. The evidence presented in this review is generally of low quality. Better designed studies with standardised reporting of outcome measurement instruments are required to determine the effectiveness of written emotional disclosure in the management of asthma.
PICOs
Plain language summary
Writing about emotional topics for asthma control and well‐being
Background
Stress may cause worsening of asthma. Previous studies showed that "written emotional disclosure," an activity that encourages people to write about stressful experiences, helps to reduce stress and improve well‐being. Therefore written emotional disclosure may have a role in the management of asthma by reducing stress.
Review question
We reviewed the medical literature to find out whether written emotional disclosure improves lung function and asthma symptoms in asthmatic patients. We looked at studies that compared the effectiveness of completing written emotional disclosure versus writing about topics unrelated to emotion.
Study characteristics
Four studies, involving 414 participants, were included in this review. The trials lasted between two months and 12 months. One study was conducted in the UK, the other three in the USA. All studies compared emotional disclosure writing versus non‐stressful writing. Three studies were conducted in adult participants and one in adolescents. The average age of participants ranged from 14 to 43 years. In all trials, most of the participants were female.
Key results
There is no evidence to support that written emotional disclosure is helpful in improving lung function or symptoms in patients with asthma. However, disclosure may be beneficial for patients' perceptions of their own asthma control. Based on evidence obtained from the studies, we are not able to draw conclusions about the role of written emotional disclosure in quality of life, psychological well‐being, asthma medication use or use of healthcare facilities for asthma‐related problems. Better designed studies are necessary to determine the effects of written emotional disclosure for patients with asthma.
Quality of the evidence
Our interpretation of the studies was limited by variation in study settings, topics of the non‐stressful writing exercise and study duration. The evidence presented in this review is generally of low quality. This summary was current to January 2014.
Authors' conclusions
Summary of findings
| Written emotional disclosure compared with neutral writing for asthma | ||||||
| Patient or population: adults and children with asthma Settings: home, healthcare, community and university settings Intervention: written emotional disclosure Comparison: neutral writing | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No. of participants | Quality of the evidence | Comments | |
| Assumed risk | Corresponding risk | |||||
| Neutral writing | Written emotional disclosure | |||||
| Average FEV1 % predicted value Follow‐up: 2 to 3 months | Mean FEV1 % predicted ranged across control groups from | Mean FEV1 % predicted in the intervention groups was (‐0.61% lower to 7.47% higher) | 286 (4 studies) | ⊕⊝⊝⊝ | Fixed effect I2 = 2% | |
| Average FVC value Follow‐up: 2 to 3 months | See comment | Mean FVC in the intervention groups was (‐0.30 lower to 0.26 higher ) | SMD ‐0.02 (‐0.30 to 0.26) | 197 (2 studies) | ⊕⊕⊝⊝ | Fixed effect I2 = 0% As studies reported FVC on different scales, we pooled using |
| Quality of life: Marks Asthma Quality of Life Questionnaire Follow‐up: 3 months (higher score indicated greater impact on quality of life; scales from 1 to 7) | See comment | See comment | 108 | ⊕⊕⊝⊝ | Only 1 trial contributed to this outcome, so we were unable to pool data | |
| Asthma symptoms Follow‐up: 2 to 3 months (different self report questionnaires, lower scores mean fewer symptoms) | Mean symptom score for control group ranged from 11.05 to 18.25 | Mean asthma symptoms in the intervention groups were (‐0.52 lower to 0.09 higher ) | SMD ‐0.22 (‐0.52 to 0.09) | 166 | ⊕⊕⊝⊝ | As studies reported asthma symptoms on different scales, we pooled using |
| Asthma control Follow‐up: 2 to 3 months (different instruments) | See comment | Mean asthma control in the intervention groups was (0.01 higher to 0.58 higher ) | SMD 0.29 (95% CI 0.01 to 0.58) | 194 (2 studies) | ⊕⊕⊝⊝ | Fixed effect I2 = 0% As studies reported asthma control on different scales, we pooled using |
| Beta agonist use; puffs/d Follow‐up: 3 months | See comment | See comment | 117 (1study) | ⊕⊕⊝⊝ | Only one trial contributed | |
| Asthma distress; Asthma Bother Profile Follow‐up: 3 months | See comment | See comment | 101 (1 study) | ⊕⊕⊝⊝ | Only one trial contributed | |
| *The basis for the assumed risk (e.g. median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence. | ||||||
| 1Outcome assessors were not blinded in 3 of 4 studies. 2Outcome assessors were not blinded in 1 of 2 studies. 3One study was judged to be at high risk of bias for selective reporting. 4Confidence interval includes important benefit and no effect. 5Single study. 6Wide confidence interval. | ||||||
Background
Description of the condition
Asthma is a chronic inflammatory disease that is associated with heightened irritability of the airways and reversible, episodic airway obstruction (Beasley 2004). The World Health Organization (WHO) estimates that 235 million people currently suffer from asthma (WHO 2013); furthermore, rates of asthma are likely to increase as more communities become urbanised (Beasley 2004). This continued growth will generate an additional treatment and diagnostic burden for healthcare systems, affecting both developed and developing countries. Despite the availability of a range of pharmaceutical treatments for people with asthma, many still experience residual and troublesome symptoms that impair their quality of life. Thus, there remains a need for complementary interventions that are effective, easily accessible and ideally low in cost.
Description of the intervention
The emotional disclosure intervention (also known as expressive writing) was originally developed by Pennebaker and Beall in 1986 (Pennebaker 1986)and was based on the idea that being unable to share experiences or inhibiting emotions following a stressful or traumatic event is associated with poorer psychological and physical health (Pennebaker 1986a). The emotional disclosure intervention asks people to disclose traumatic or stressful experiences through writing. Proponents suggest that emotional disclosure can have positive effects on both physical and psychological health, and several theories have been proposed to explain these benefits. Initial explanations stemmed from the Freudian theory of catharsis, whereby inhibiting stressful or traumatic events leads to impairment of physical and mental health, which can be alleviated by disclosure (Pennebaker 1986a; Pennebaker 1993). More recently, emerging theories regarding cognitive processing have suggested that enabling individuals to write about a stressful or traumatic experience allows creation of a coherent narrative, which, in turn, leads to insight into and an understanding of the experience (Pennebaker 1993). A further explanation is that benefit occurs via self regulation, as written disclosure of both real and imaginary trauma provides the individual with a mastery experience, allowing expression and control of emotions (Lepore 2002). Emotional disclosure can also be conducted within 'talking therapies'; however, this type of emotional disclosure may be influenced by different psychological processes and is excluded from this systematic review. If effective, written emotional disclosure would provide an inexpensive and safe adjunct to pharmacotherapy in the routine care of asthma.
Why it was important to complete this review
Several research syntheses regarding written emotional disclosure have reported variable and conflicting results.
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Smyth 1998 reviewed 13 studies conducted with healthy participants. Results suggested that written emotional disclosure significantly enhanced physical health, psychological well‐being, physiological functioning and general functioning.
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Frisina 2004 carried out a meta‐analysis of nine studies conducted in people diagnosed with physical or psychiatric disorders; the analysis demonstrated a positive effect on physical health outcomes.
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Meads 2005 carried out a meta‐analysis of 60 studies that included both healthy participants and those with preexisting morbidity. The analysis showed no significant difference in health centre visits between treatment groups. However, Meads 2005 excluded many positive studies from the analysis because they did not report mean differences, even though effect sizes could be calculated from other reported data. This biased the analysis towards a negative result.
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Frattaroli 2006 carried out a meta‐analysis by using a comprehensive definition of a disclosure task that involved writing (or talking) about a real or imagined significant life event or personal topic. Included were 146 trials of healthy participants, trials including participants with a diverse range of health conditions and trials in participants who had experienced traumatic events such as sexual assault. In contrast to earlier meta‐analyses (Frisina 2004; Smyth 1998), Frattaroli 2006 calculated composite effect sizes drawn from data extracted from a number of different rating scales related to psychological and physical health. This analysis showed statistically significant differences favouring disclosure.
All previously published reviews have explored the effects of written emotional disclosure on broad populations that may not be suitable for meta‐analysis. Such an approach overlooks that differing illnesses can place different stressors on a person (e.g. through the invasiveness of needed medical treatment or the disease prognosis), and so the effects of written emotional disclosure may be disease specific. The specific effects of written emotional disclosure for patients with asthma are unclear.
In asthma, a well‐evidenced link has been identified between stress and exacerbation of asthma symptoms (Wright 1998). Therefore, in comparison with other illness, written emotional disclosure has a particular potential to affect health outcomes through reduction of stress caused by distressing or traumatic experiences. Two Cochrane systematic reviews (Yorke 2005; Yorke 2009) have focused on the use of psychological interventions for asthma (one focusing on adults, the other focusing on children) and were unable to draw conclusions. As written emotional disclosure is not delivered by a therapist, it did not fall within the scope of either of these reviews. The current review complements these two existing Cochrane reviews by exploring the effectiveness of expressive writing for people with asthma.
In summary, existing published reviews on written emotional disclosure have used small and heterogeneous samples with diverse outcome measures, thereby preventing firm conclusions. Existing reviews on psychological therapies for asthma have not included written emotional disclosure. This review addresses these problems by focusing specifically on the effects of emotional disclosure for patients with asthma.
Objectives
This review aims to determine the effectiveness of written emotional disclosure for people with asthma, specifically, to assess:
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overall efficacy of emotional disclosure compared with emotionally neutral writing on self reported quality of life in people with asthma;
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overall efficacy of emotional disclosure compared with emotionally neutral writing on objective measures of health outcome in people with asthma; and
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comparative efficacy of different types of emotional disclosure for people with asthma.
Methods
Criteria for considering studies for this review
Types of studies
We included randomised controlled trials (RCTs) assessing the effectiveness of an emotional writing intervention for people with asthma. We excluded quasi‐randomised trials.
Types of participants
This review included people diagnosed with asthma by a general practitioner or consultant or according to standard guidelines for diagnosis (e.g. British Thoracic Society, American Thoracic Society). We included both men and women of any age.
Studies conducted in all settings (including hospital, family practice and the community) were considered, as no preexisting theoretical reason suggested that setting affected outcome, and this approach makes the findings more generalisable.
Types of interventions
Written emotional disclosure interventions based on the protocol developed by Pennebaker et al (Pennebaker 1986) or on the guided disclosure intervention developed by Gidron et al (Gidron 2002) were included.
Studies that included a control group given a non‐emotional writing intervention (such as writing about time management) were included in the review. Studies that included a non‐writing control group were excluded to control for the potential effect of the writing process itself and/or the allocation of time to reflect on outcomes. Only studies with a neutral writing control group were included to ensure that any observed treatment effects were due to the emotional component of the writing rather than to the writing itself.
Types of outcome measures
Primary outcomes
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Physiological measure of lung function (forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC)).
Secondary outcomes
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Self reported quality of life using a validated questionnaire.
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Self reported symptom scores using a validated questionnaire.
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Self reported medication use.
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Scheduled or unscheduled healthcare utilisation.
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Psychological well‐being based on a validated questionnaire.
Search methods for identification of studies
Electronic searches
We identified trials from the Cochrane Airways Group Specialised Register of trials (CAGR); the Cochrane Central Register of Controlled Trials (CENTRAL) 2014, Issue 12, part of The Cochrane Library; MEDLINE (Ovid) 1950 to January week 1, 2014; EMBASE (Ovid) 1974 to week 2, 2014; CINAHL (Ebsco) 1982 to January 2014; AMED (Ebsco) 1985 to January 2014; and PsycINFO (Ovid) 1806 to January, week 1, 2014. The search strategies used for each database are presented in Appendix 1. The latest searches were conducted in January 2014, with no restriction on language or type of publication. Handsearched conference abstracts and grey literature were searched through the CENTRAL database and the CAGR.
Searching other resources
We reviewed reference lists of all primary studies and review articles to look for additional references. Authors of identified trials were contacted and were asked to identify other published and unpublished studies. We contacted experts in the field, including Professor JW Pennebaker, who originated the written emotional disclosure protocol. The search attempted to identify all relevant studies, irrespective of language.
Data collection and analysis
Selection of studies
Two of three review authors (AT, PH and PP) independently assessed the relevance of abstracts identified by the search against the inclusion criteria. Full‐text articles were obtained for studies potentially fulfilling the inclusion criteria. The same review authors independently assessed each study against the inclusion criteria using a study selection form. Disagreements were resolved through discussion to reach a consensus decision with all review authors. Contact with study investigators was made when necessary to clarify eligibility. Reasons for inclusion or exclusion were recorded on the study selection form.
Data extraction and management
Data from each eligible study were extracted using a specifically designed form. Data extraction was completed independently by two review authors (PH and PP). The review authors were not blinded to the study authors nor to the publishing journal of each paper. On completion, results were compared and inconsistencies resolved by discussion. Aspects of study design, participant characteristics, interventions and outcomes were described and entered into RevMan 5 software.
We attempted to contact the authors of studies by using corresponding email addresses provided in the original articles or institutional Websites to ask for additional information required for the review that had not been included in the original article.
Assessment of risk of bias in included studies
Two review authors (PP and PH) independently performed the risk of bias assessment for each study. To facilitate assessment, information was collected by using The Cochrane Collaboration tool to assess risk of bias (Table 8.5.a in the Cochrane Handbook for Systematic Reviews of Interventions, version 5.0.0). For each domain, the procedures undertaken for each study were documented, including verbatim quotes. A judgement was made as to the possible risk of bias for each of the six domains, with the answer 'low' indicating low risk and the answer 'high' indicating high risk of bias. If insufficient detail was reported in the study, a judgement of 'unclear' was made, and the original study investigators were contacted to provide more information with the judgement adjusted accordingly. Graphic representations of potential bias within and across studies were computed using RevMan 5 software.
Measures of treatment effect
For continuous data, end point scores were expressed as mean differences (MDs) or standardised mean differences (SMDs) with associated 95% confidence intervals (CIs). For dichotomous data, the number of participants for each outcome event was entered into a 2 × 2 contingency table, and the fixed‐effect odds ratio (OR) with 95% CIs was reported.
Dealing with missing data
We contacted the authors of studies to ask for information not reported in the original article that was required for the review.
Assessment of heterogeneity
We assessed heterogeneity of the trials through visual inspection of forest plots and calculation of the I2 statistic in RevMan 5. We used a 50% limit to indicate substantial heterogeneity (Higgins 2011) and intended to explore the reasons for statistical variation if results exceeded this limit.
Assessment of reporting biases
We intended to use funnel plots to assess the possibility of publication bias if we found more than 10 studies; however, given the relatively small number of studies reporting each outcome, we did not undertake such assessment.
Data synthesis
Data extracted from each study were entered into a summary table to enable comparison of study characteristics, quality and results. As variation was noted in numbers and/or times of follow‐up measurement across studies, we have extracted and presented data for short‐term (≤ three months), medium‐term (> three months to six months) and long‐term (> six months) outcomes. If more than one measurement was taken during an outcome period, we used the longest follow‐up time measurement in our analysis.
We performed the analysis with RevMan 5 software, using fixed‐effect models.
Subgroup analysis and investigation of heterogeneity
We planned to evaluate the effectiveness of written emotional disclosure with regard to:
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asthma severity (as defined by FEV1 baseline reading); and
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age (< 18 years vs ≥ 18 years).
We planned to present and analyse self reported quality of life at one, three and six months' follow‐up rather than using only the longest follow‐up time.
None of these analyses were undertaken because of the small number of studies in the meta‐analysis.
Sensitivity analysis
Sensitivity analyses that were planned to recalculate the meta‐analysis by excluding studies of poorer quality were not undertaken because of the small number of studies.
Results
Description of studies
Study design
All four included studies were RCTs. Three studies were published between 1999 and 2006 (Harris 2005; Smyth 1999; Warner 2006). One study was unpublished, the draft of which was provided by the author (Smith 2013). Trial duration varied from two months to 12 months. All included studies were conducted in developed countries: One study was conducted in the UK (Smith 2013), the other three in the USA. Three studies had one intervention group and one control group (Smith 2013; Smyth 1999; Warner 2006). The fourth study (Harris 2005) consisted of two intervention groups and one control group, but for the purposes of this review, only the results obtained for the expressive writing intervention arm have been included. Only one study was described as double‐blind (Smith 2013).
Study participants
A total of 414 participants were included in this review. Three studies were conducted in adult participants (Harris 2005; Smith 2013; Smyth 1999) and one in adolescents (Warner 2006). All studies, except Warner 2006, reported a sample size calculation. The numbers of eligible and randomly assigned participants were detailed in all studies. Harris 2005 approached 168 participants; 163 were eligible and 137 were randomly assigned. Smith 2013 screened 267 eligible participants, and 146 were randomly assigned. Warner 2006 screened 222 participants, 70 of whom were eligible, and all 70 were randomly assigned. Smyth 1999 identified 210 potentially eligible participants; 180 were eligible, and only 61 were randomly assigned. Three studies provided a flow diagram of participants' adherence and dropout rates at various phases of the study and detailed the reasons for attrition (Harris 2005; Smith 2013; Smyth 1999). The fourth study reported the magnitude of attrition between pre/post assessments but did not report the reason for the withdrawal (Warner 2006). However, this study reported that the characteristics of non‐completers were similar to those of completers.
Average age of participants in the trials ranged from 14 years (Warner 2006) to 43 years (Harris 2005). In all trials, most of the participants were female. Settings of studies varied and included home (Smith 2013), healthcare settings (Harris 2005; Smyth 1999; Warner 2006) and community and university settings (Harris 2005). Presentation with physician‐diagnosed asthma was an entry criterion in all studies. Asthma severity was measured in a variety of ways. Warner 2006 included participants with at least mild persistent asthma, Smith 2013 included participants who required regular inhaled medication (British Thoracic Society step two and above) and severity was not reported in other studies. Participants in the trials were excluded if they were unable to write for 20 minutes (Harris 2005; Smyth 1999), had received psychotherapy or had a defined psychiatric disorder (Harris 2005; Smith 2013; Smyth 1999; Warner 2006), had used a medication that could interfere with symptom reports (Smyth 1999; Warner 2006), had been diagnosed with chronic obstructive pulmonary disease (COPD) by a physician (Harris 2005) or had only seasonal or exercise‐induced asthma (Warner 2006). In an attempt to exclude patients who may have COPD, Smith 2013 excluded patients over 45 years of age. Smith 2013 also excluded patients who were unable to understand English or who had work or travel commitments during the trial period.
Outcome measures
A variety of outcomes were measured in the studies. Lung function was assessed in all studies: Harris 2005 measured FEV1 and FVC % predicted, Smith 2013 reported FEV1 % predicted and FVC (absolute value); other studies measured FEV1 % predicted only. Only one study measured quality of life (Smith 2013). Asthma symptoms were evaluated in two studies (Smith 2013 used a validated questionnaire; Warner 2006 used a scale that had been previously used but not clearly validated). Medication use was measured in one study (Smith 2013) and healthcare utilisation in two studies (Harris 2005; Smith 2013). In addition, some researchers measured psychological well‐being such as asthma distress (Smith 2013), stress (Harris 2005), positive affect and negative affect, with internalisation of behaviour problems (Warner 2006).
Intervention used
All studies adapted the intervention from the brief written emotional disclosure exercise developed by Pennebaker and Beall (Pennebaker 1986). Participants in the intervention group wrote on the most stressful experience that they had ever undergone. The written exercise for control groups varied across studies and included writing on neutral events of the previous day (Harris 2005), writing a factual account of a specific activity during the day (Smith 2013), writing plans for the day (Smyth 1999) and writing about time management (Warner 2006). In three studies, participants wrote for 20 minutes a day for three consecutive days (Smith 2013; Smyth 1999; Warner 2006); in one study, three sessions were spread over three consecutive weeks (Harris 2005). Warner 2006 encouraged participants to write on the same topic for three sessions, but participants in other studies were instructed to write about the same topic or to move from one topic to another. Location of the writing session varied across studies: Sessions occurred at home (Smith 2013; Warner 2006 ) or in the laboratory (Smyth 1999) or in both places (Harris 2005). In all studies, participants were asked to write continuously without worrying about spelling or writing style.
Results of the search
A total of 517 references were identified by electronic literature searches up to January 2014. Six additional references were identified through other sources. Of these 523, 17 studies were retrieved for further scrutiny. The article selection process is presented in a PRISMA diagram (Figure 1).
Flow chart of article selection process for the review.
Included studies
This review includes four randomised controlled trials that met the eligibility criteria. Summary details of the included studies are given below. Details of individual studies are summarised in the table Characteristics of included studies.
Excluded studies
In total, 13 studies failed to meet the eligibility criteria; reasons for exclusion have been provided in Characteristics of excluded studies. Seven studies (54%) did not include written emotional disclosure as an intervention; two (15%) were qualitative studies, one trial was non‐randomised (8%) and another was a narrative review of written emotional disclosure in different conditions (8%). Of the trials remaining, one (8%) consisted of multiple interventions, and it was impossible to tease out the effects of disclosure writing alone; the other trial (8%) also included participants with COPD and idiopathic pulmonary fibrosis. See Characteristics of excluded studies.
Risk of bias in included studies
Overall, the methodological quality of papers was good. Complete details on risk of bias judgements are described in Characteristics of included studies and in Figure 2 and Figure 3.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.
Allocation
Sequence generation was carried out adequately in all studies; computer‐generated programmes were used for randomisation. All studies used sealed envelopes for allocation and hence were judged to be at low risk of bias for allocation concealment (Harris 2005; Smith 2013; Smyth 1999; Warner 2006).
Blinding
Only one of the four included trials was double‐blind (Smith 2013). The other three studies (Harris 2005; Smyth 1999; Warner 2006) reported blinding of participants but did not describe blinding of outcome assessors; hence we judged these three studies to be at high risk of bias.
Incomplete outcome data
All studies had similar numbers of dropouts in the intervention and control groups and similar reasons for missing data and therefore were judged as having low risk of attrition bias. Only one study reported intervention‐related dropout (Harris 2005); two participants in the disclosure group discontinued, as they feared the writing task would be too upsetting
Selective reporting
Two studies reported measuring outcomes including lung function, asthma symptoms and psychological well‐being (Smith 2013; Warner 2006 ) and thus were judged to be at low risk of bias for selective reporting. Harris 2005 reported FEV1 % predicted and FVC % predicted, and Smyth 1999 reported FEV1 % predicted only. Corresponding authors of these two studies were contacted to provide further information on other outcomes. Harris 2005 provided data on additional outcomes (such as perceived stress, asthma control) and thus was judged to be at low risk of bias. Smyth 1999 confirmed the measurement of additional outcomes but provided no analyses of the data; hence, the study was judged to be at high risk of bias for selective reporting.
Effects of interventions
See: Summary of findings for the main comparison
Relevant data were entered and forest plots created. However, we were able to pool only the data for FEV1 % predicted, FVC, asthma symptoms and asthma control. We could not pool data for other outcomes because of divergent outcome measurements and measurement tools. Results are presented below for each outcome, starting with our primary outcome of lung function.
Lung function
FEV1
All four studies measured FEV1 % predicted (Harris 2005; Smith 2013; Smyth 1999; Warner 2006). A pooled analysis of the homogenous data (I2 = 2%; P value 0.38), including a total of 146 intervention and 135 control participants, indicated no statistically significant differences in FEV1 % predicted between the emotional disclosure group and the control group at short‐term follow‐up (MD 3.43%, 95% CI ‐0.61% to 7.47%). Evidence was rated as of very low quality after it had been downgraded for lack of assessor blinding, publication bias and imprecision because the confidence intervals included significant benefit and no effect.
A pooled result from two studies on 176 participants (Harris 2005; Smith 2013) showed that disclosure writing did not significantly improve FEV1 % predicted in participants with asthma at medium‐term follow‐up (MD 3.61%, 95% CI ‐1.95 to 9.16). Only one study measured FEV1 % predicted at long‐term follow‐up (Smith 2013) and reported no significant benefit of disclosure writing in participants with asthma (MD 5.89%, 95% CI ‐0.61 to 12.39) (Figure 4).
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.1 Average FEV1 % predicted value.
FVC
Two studies on 197 participants measured FVC (Harris 2005; Smith 2013). Harris 2005 reported FVC % predicted values, and Smith 2013 reported absolute FVC values. A pooled result from these two studies indicated that disclosure writing did not result in significant improvement in FVC in participants with asthma at short‐term follow‐up (SMD ‐0.02, 95% CI ‐0.30 to 0.26). The outcome was rated as of low quality after it had been downgraded for lack of assessor blinding and imprecision because the confidence intervals included significant benefit and no effect.
One study measured FVC (absolute value) at medium‐ and long‐term follow‐up (Smith 2013). This study found no significant differences in FVC values between the disclosure writing group and the control group at both follow‐up periods (Figure 5).
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.3 Average FVC value.
Asthma quality of life
The impact of written emotional disclosure interventions on disease‐specific quality of life was assessed in one trial (Smith 2013). This study used the Marks Asthma Quality of Life Questionnaire (Marks 1992), a validated tool in which a higher score indicates greater impairment in quality of life. No significant difference in quality of life was found between the emotional disclosure group and the control group at any point of follow‐up (Figure 6). Evidence was rated as of low quality and was downgraded for imprecision because the confidence intervals show significant benefit and no effect, and because evidence was based on a single trial.
Forest plot of comparison: 1 Written emotional disclosure versus control, outcome: 1.3 Quality of life; Marks Asthma Quality of Life Questionnaire.
Asthma symptoms
Two studies including 166 participants reported symptoms as an outcome measure (Smith 2013; Warner 2006). In Smith 2013, asthma symptoms were measured using the Symptom Score Questionnaire (SSQ) (Wasserfellan 1997), a 23‐item validated scale in which a lower score indicates fewer symptoms. Warner 2006 used the nine‐item Asthma Sum Scale (Wahlgren 1997) to measure symptoms. A pooled result from these two studies indicated that disclosure writing does not improve asthma symptoms at short‐term follow‐up (SMD ‐0.22, 95% CI ‐0.52 to 0.09). The outcome was rated as of low quality after it had been downgraded for lack of assessor blinding and imprecision because the confidence intervals included significant benefit and no effect.
One study measured asthma symptoms at medium‐ and long‐term follow‐up (Smith 2013); this study reported no significant benefit of disclosure writing for asthma symptoms at either follow‐up (Figure 7).
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.5 Asthma symptoms.
Asthma control
Two studies on 194 participants measured asthma control (Harris 2005; Smith 2013) but used different instruments. Harris 2005 used the Asthma Control Questionnaire (Juniper 1999) to measure the adequacy of asthma control and changes in asthma control as a result of emotional disclosure writing. Smith 2013 used the Asthma Control Test, a validated tool in which higher scores reflect greater asthma control (Nathan 2004). A pooled result from these two studies indicated that disclosure writing results in short‐term improvement in asthma control (SMD 0.29, 95% CI 0.01 to 0.58). Evidence was rated as of low quality and had been downgraded for imprecision (wide confidence intervals) and lack of assessor blinding.
Only one study measured asthma control at medium‐term and long‐term follow‐up (Smith 2013). The beneficial effect of disclosure writing for asthma control was not statistically significant at later follow‐up (Figure 8).
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.6 Asthma control.
Medication use (puffs/d)
Smith 2013 examined the effects of written emotional disclosure for medication use (inhaled corticosteroids and beta agonists (MD ‐1.62, 95% CI ‐2.62 to ‐0.62)). This study found that the disclosure group used significantly less beta agonist compared with the control group at short‐term follow‐up. However, no significant differences in the use of these medications were found between groups at later follow‐up (Figure 9; Figure 10). The outcome was rated as of low quality after it had been downgraded for imprecision and for evidence based on a single trial.
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.7 Beta agonist use; puffs/d.
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.8 Inhaled corticosteroid use; puffs/d.
Healthcare utilisation
Healthcare utilisation was measured in two studies; Harris 2005 measured utilisation over a two‐month period, whereas Smith 2013 recorded measurements over a 12=month period. Harris 2005 found no significant differences between groups on change in healthcare use (data to support this were not reported in the study, apart from data for healthcare use, which were available for 13 of 114 participants). Smith 2013 also revealed no significant differences in the odds of healthcare utilisation in the intervention groups when compared with the control group: OR 0.99 (95% CI 0.37 to 2.66) (Figure 11).
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.9 Healthcare utilisation.
Psychological symptoms
Distress
Smith 2013 used the Asthma Bother Profile (Hyland 1995), a 15‐item validated scale, to measure distress caused by asthma. This study found no significant differences in asthma distress between the disclosure writing group and the control group at any follow‐up period (Figure 12). The remaining trials (Harris 2005; Smyth 1999; Warner 2006) did not provide data on distress. The outcome was rated as of very low quality after it had been downgraded for imprecision because the confidence intervals included significant benefit and no effect, and because evidence was based on a single trial .
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.10 Asthma distress; Asthma Bother Profile.
Perceived stress
Harris 2005 measured stress caused by asthma using the 14‐item Perceived Stress Scale (Cohen 1983). This study found no significant differences between intervention and control groups in measurements of stress (data not reported). The remaining studies (Smith 2013; Smyth 1999; Warner 2006 ) did not include data on stress.
Discussion
Summary of main results
This review identified four trials measuring the effectiveness of written emotional disclosure in the treatment of participants with asthma. Overall, this review failed to find evidence that emotional disclosure writing improves pulmonary function and symptoms in participants with asthma. These studies differed in reported outcomes, outcome measurement tools and frequency and/or time of follow‐up measurements, which, in turn, limited our ability to summarise the pool effect for other outcomes except FEV1 % predicted, FVC, asthma symptoms and asthma control. Although one study (Smyth 1999) reported significantly greater FEV1 % predicted at all follow‐up measurements, this study recruited participants with more severe conditions (FEV1 % predicted at baseline was 64%), which meant that there was more room for improvement in lung function compared with participants with less severe conditions who had been recruited in other trials (baseline FEV1 % predicted value: 73% in Harris 2005, 87% in Smith 2013 and 94% in Warner 2006).
Quality of life was measured in one study (Smith 2013), but no beneficial effect of disclosure writing for quality of life of participants with asthma was found. Asthma symptoms were assessed in two studies (Smith 2013; Warner 2006); however, the symptom measurement tools in these studies varied. For example, Smith 2013 used the Symptom Score Questionnaire (Wasserfellan 1997), and Warner 2006 used the Asthma Sum Scale (Wahlgren 1997), thus making the rigour of this assessment difficult to ascertain. Two studies measured asthma control (Harris 2005; Smith 2013); a pooled result from these studies indicated that disclosure writing results in improvement in asthma control at short‐term follow‐up.
In terms of medication use, Smith 2013 reported reduced use of a bronchodilator at three months but found no significant difference in the use of steroid inhalers. This may be explained by the fact that for many patients, steroid dosing is regular, whereas a bronchodilator medication is prescribed for use ‘as required’ to control breakthrough symptoms. Hence, improved symptom control and reduced necessity to intervene with rescue medication are consistent observations.
Of the four studies included in the review, only two measured healthcare utilisation (Harris 2005; Smith 2013). Both studies found no significant differences between groups in healthcare use. Both studies used self report measures and hence may not reflect accurately true actual healthcare utilisation.
Psychological well‐being was measured in three studies (Harris 2005; Smith 2013; Warner 2006); however, the outcomes examined were diverse. There seems to be no consensus as to which psychological outcomes are conceptually linked to asthma or to the written emotional disclosure intervention being studied. For example, Harris 2005 measured perceived stress, and Smith 2013 measured asthma distress. Warner 2006 measured positive and negative affect, along with internalising behaviour, in adolescents. For the purpose of this review, we reported only distress and stress, as the other outcomes were not prespecified in our protocol and were more child specific. One study (Smith 2013) reported greater distress in the disclosure group compared with the control group at one month of follow‐up.
RCTs evaluating written emotional disclosure for asthma are rare. The few studies identified were relatively homogeneous in terms of the intervention provided to experimental groups; all studies adapted a brief written emotional expression exercise developed by Pennebaker and Beall (Pennebaker 1986). However, many variations existed, especially in terms of the intervention provided to control groups, location (home and/or laboratory) and timing (daily sessions or weekly sessions) of the written exercise session, as well as instruction on flexibility of the topic (same topic for all sessions or moved from one topic to another). These procedural differences may have resulted in some diversity, which was further complicated by the multiplicity of outcomes. Although the diversity of outcomes measured in the studies reflects the potential breadth of the impact of written emotional disclosure, no consensus has yet been reached on which outcomes a written emotional disclosure might influence and the conceptual link between them.
Various moderating factors such as sample characteristics, outcome type (self report vs objective data), dose of the intervention and focus of the writing task (past traumatic event, ongoing traumatic event or both) may attenuate or enhance the effects of written emotional disclosure (Smyth 1998). However, in the current context of uncertainty around the effectiveness of disclosure writing for patients with asthma, it is not appropriate to look for mediators of this effect.
Overall completeness and applicability of evidence
We conducted a thorough systematic search for published and unpublished trials and could extract data from only four trials. At present, there is no evidence to support that written emotional disclosure provides significant benefit in improving the lung function and symptoms of patients with asthma in general.
Quality of the evidence
This review included four studies with 414 participants. Individual studies were small, ranging from 61 to 146 participants. Key methodological limitations included lack of assessor blinding in three of the four studies, and outcomes other than lung function were limited to a subset of studies; asthma symptoms and asthma control were measured in two, and all other outcomes were measured in only one trial. Thus, the quality of evidence for many outcomes was rated as low or very low.
Potential biases in the review process
We corresponded with the authors of all included trials to identify other published and non‐published studies in the area. We followed a prespecified protocol for trial selection and data extraction, and two review authors independently conducted the process. Nevertheless, we acknowledge that we might have missed unpublished trials, which might change our confidence in the conclusions. Some of the review authors were involved in a trial of written emotional disclosure for asthma. We have declared our interest in the Declarations of interest section.
Agreements and disagreements with other studies or reviews
This is the first review to focus on the effects of written emotional disclosure in the treatment of patients with asthma. It summarises the best evidence available to January 2014. This review is unable to find any evidence to support that written emotional disclosure improves lung function and asthma symptoms in asthmatic patients, but written emotional disclosure may have some beneficial effect on asthma control. Cochrane reviews on psychological interventions for asthma in children (Yorke 2005) and adults (Yorke 2009) were unable to draw firm conclusions because of the absence of an adequate evidence base. Previous reviews exploring the effects of written emotional disclosure for healthy and clinical participants have produced different results; three reviews (Frattaroli 2006; Frisina 2004; Smyth 1998) produced positive results, but a review by Meads 2005 produced a neutral result. This review, by focusing on a single disease, allows the evidence to be explored in greater depth.
Flow chart of article selection process for the review.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.1 Average FEV1 % predicted value.
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.3 Average FVC value.
Forest plot of comparison: 1 Written emotional disclosure versus control, outcome: 1.3 Quality of life; Marks Asthma Quality of Life Questionnaire.
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.5 Asthma symptoms.
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.6 Asthma control.
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.7 Beta agonist use; puffs/d.
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.8 Inhaled corticosteroid use; puffs/d.
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.9 Healthcare utilisation.
Forest plot of comparison: 1 Written emotional disclosure (WED) versus control, outcome: 1.10 Asthma distress; Asthma Bother Profile.
Comparison 1 Written emotional disclosure (WED) versus control, Outcome 1 Average FEV1 % predicted value.
Comparison 1 Written emotional disclosure (WED) versus control, Outcome 2 Change in FEV1 % predicted in short term.
Comparison 1 Written emotional disclosure (WED) versus control, Outcome 3 Average FVC value.
Comparison 1 Written emotional disclosure (WED) versus control, Outcome 4 Quality of life; Marks Asthma Quality of Life Questionnaire.
Comparison 1 Written emotional disclosure (WED) versus control, Outcome 5 Asthma symptoms.
Comparison 1 Written emotional disclosure (WED) versus control, Outcome 6 Asthma control.
Comparison 1 Written emotional disclosure (WED) versus control, Outcome 7 Beta agonist use; puffs/d.
Comparison 1 Written emotional disclosure (WED) versus control, Outcome 8 Inhaled corticosteroid use; puffs/d.
Comparison 1 Written emotional disclosure (WED) versus control, Outcome 9 Healthcare utilisation.
Comparison 1 Written emotional disclosure (WED) versus control, Outcome 10 Asthma distress; Asthma Bother Profile.
| Written emotional disclosure compared with neutral writing for asthma | ||||||
| Patient or population: adults and children with asthma Settings: home, healthcare, community and university settings Intervention: written emotional disclosure Comparison: neutral writing | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No. of participants | Quality of the evidence | Comments | |
| Assumed risk | Corresponding risk | |||||
| Neutral writing | Written emotional disclosure | |||||
| Average FEV1 % predicted value Follow‐up: 2 to 3 months | Mean FEV1 % predicted ranged across control groups from | Mean FEV1 % predicted in the intervention groups was (‐0.61% lower to 7.47% higher) | 286 (4 studies) | ⊕⊝⊝⊝ | Fixed effect I2 = 2% | |
| Average FVC value Follow‐up: 2 to 3 months | See comment | Mean FVC in the intervention groups was (‐0.30 lower to 0.26 higher ) | SMD ‐0.02 (‐0.30 to 0.26) | 197 (2 studies) | ⊕⊕⊝⊝ | Fixed effect I2 = 0% As studies reported FVC on different scales, we pooled using |
| Quality of life: Marks Asthma Quality of Life Questionnaire Follow‐up: 3 months (higher score indicated greater impact on quality of life; scales from 1 to 7) | See comment | See comment | 108 | ⊕⊕⊝⊝ | Only 1 trial contributed to this outcome, so we were unable to pool data | |
| Asthma symptoms Follow‐up: 2 to 3 months (different self report questionnaires, lower scores mean fewer symptoms) | Mean symptom score for control group ranged from 11.05 to 18.25 | Mean asthma symptoms in the intervention groups were (‐0.52 lower to 0.09 higher ) | SMD ‐0.22 (‐0.52 to 0.09) | 166 | ⊕⊕⊝⊝ | As studies reported asthma symptoms on different scales, we pooled using |
| Asthma control Follow‐up: 2 to 3 months (different instruments) | See comment | Mean asthma control in the intervention groups was (0.01 higher to 0.58 higher ) | SMD 0.29 (95% CI 0.01 to 0.58) | 194 (2 studies) | ⊕⊕⊝⊝ | Fixed effect I2 = 0% As studies reported asthma control on different scales, we pooled using |
| Beta agonist use; puffs/d Follow‐up: 3 months | See comment | See comment | 117 (1study) | ⊕⊕⊝⊝ | Only one trial contributed | |
| Asthma distress; Asthma Bother Profile Follow‐up: 3 months | See comment | See comment | 101 (1 study) | ⊕⊕⊝⊝ | Only one trial contributed | |
| *The basis for the assumed risk (e.g. median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence. | ||||||
| 1Outcome assessors were not blinded in 3 of 4 studies. 2Outcome assessors were not blinded in 1 of 2 studies. 3One study was judged to be at high risk of bias for selective reporting. 4Confidence interval includes important benefit and no effect. 5Single study. 6Wide confidence interval. | ||||||
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 Average FEV1 % predicted value Show forest plot | 4 | Mean Difference (IV, Fixed, 95% CI) | Subtotals only | |
| 1.1 Short‐term | 4 | 281 | Mean Difference (IV, Fixed, 95% CI) | 3.43 [‐0.61, 7.47] |
| 1.2 Medium‐term | 2 | 176 | Mean Difference (IV, Fixed, 95% CI) | 3.61 [‐1.95, 9.16] |
| 1.3 Long‐term | 1 | 116 | Mean Difference (IV, Fixed, 95% CI) | 5.89 [‐0.61, 12.39] |
| 2 Change in FEV1 % predicted in short term Show forest plot | 2 | 195 | Mean Difference (IV, Fixed, 95% CI) | 1.68 [‐0.82, 4.18] |
| 3 Average FVC value Show forest plot | 2 | Std. Mean Difference (IV, Fixed, 95% CI) | Subtotals only | |
| 3.1 Short‐term | 2 | 197 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.02 [‐0.30, 0.26] |
| 3.2 Medium‐term | 1 | 118 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.35 [‐0.72, 0.01] |
| 3.3 Long‐term | 1 | 116 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.05 [‐0.42, 0.31] |
| 4 Quality of life; Marks Asthma Quality of Life Questionnaire Show forest plot | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 4.1 Short‐term | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 4.2 Medium‐term | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 4.3 Long‐term | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 5 Asthma symptoms Show forest plot | 2 | Std. Mean Difference (IV, Fixed, 95% CI) | Subtotals only | |
| 5.1 Short‐term | 2 | 166 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.22 [‐0.52, 0.09] |
| 5.2 Medium‐term | 1 | 112 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.00 [‐0.37, 0.37] |
| 5.3 Long‐term | 1 | 109 | Std. Mean Difference (IV, Fixed, 95% CI) | ‐0.18 [‐0.56, 0.19] |
| 6 Asthma control Show forest plot | 2 | Std. Mean Difference (IV, Fixed, 95% CI) | Subtotals only | |
| 6.1 Short‐term | 2 | 194 | Std. Mean Difference (IV, Fixed, 95% CI) | 0.29 [0.01, 0.58] |
| 6.2 Medium‐term | 1 | 114 | Std. Mean Difference (IV, Fixed, 95% CI) | 0.19 [‐0.17, 0.56] |
| 6.3 Long‐term | 1 | 109 | Std. Mean Difference (IV, Fixed, 95% CI) | 0.22 [‐0.16, 0.60] |
| 7 Beta agonist use; puffs/d Show forest plot | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 7.1 Short‐term | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 7.2 Medium‐term | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 7.3 Long‐term | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 8 Inhaled corticosteroid use; puffs/d Show forest plot | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 8.1 Short‐term | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 8.2 Medium‐term | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 8.3 Long‐term | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 9 Healthcare utilisation Show forest plot | 1 | Odds Ratio (M‐H, Fixed, 95% CI) | Subtotals only | |
| 10 Asthma distress; Asthma Bother Profile Show forest plot | 1 | Mean Difference (IV, Fixed, 95% CI) | Totals not selected | |
| 10.1 Short‐term | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 10.2 Medium‐term | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
| 10.3 Long‐term | 1 | Mean Difference (IV, Fixed, 95% CI) | 0.0 [0.0, 0.0] | |
