Comparison 1. Internet‐based cognitive and behavioural therapy (I‐C/BT) versus wait list (WL).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1.1 Severity of PTSD symptoms (post‐treatment)	8	560	Std. Mean Difference (IV, Random, 95% CI)	‐0.60 [‐0.97, ‐0.24]
1.2 Severity of PTSD symptoms (follow‐up < 6 months)	3	146	Std. Mean Difference (IV, Random, 95% CI)	‐0.43 [‐1.41, 0.56]
1.3 Dropouts	8	585	Risk Ratio (M‐H, Fixed, 95% CI)	1.39 [1.03, 1.88]
1.4 Diagnosis of PTSD after treatment	1	62	Risk Ratio (M‐H, Fixed, 95% CI)	0.53 [0.28, 1.00]
1.5 Severity of depression (post‐treatment)	5	425	Std. Mean Difference (IV, Random, 95% CI)	‐0.61 [‐1.17, ‐0.05]
1.6 Severity of depression (follow‐up < 6 months)	1	42	Mean Difference (IV, Fixed, 95% CI)	‐8.95 [‐15.57, ‐2.33]
1.7 Severity of anxiety symptoms (post‐treatment)	4	305	Std. Mean Difference (IV, Random, 95% CI)	‐0.67 [‐0.98, ‐0.36]
1.8 Severity of anxiety symptoms (follow‐up < 6 months)	1	42	Mean Difference (IV, Fixed, 95% CI)	‐12.59 [‐20.74, ‐4.44]
1.9 Quality of Life (post‐treatment)	2	221	Std. Mean Difference (IV, Random, 95% CI)	0.60 [0.08, 1.12]