Comparison 1. Written emotional disclosure (WED) versus control.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Average FEV1 % predicted value	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	2	195	Mean Difference (IV, Fixed, 95% CI)	1.68 [‐0.82, 4.18]
3 Average FVC value	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	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	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	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	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	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	1		Odds Ratio (M‐H, Fixed, 95% CI)	Subtotals only
10 Asthma distress; Asthma Bother Profile	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]