Mechanisms of change in Internet- and mobile-based interventions for PTSD: a systematic review and meta-analysis

Figures & data

Figure 1. Flow chart

Figure 2. Risk of bias graph

Figure 3. Forest Plot for overall efficacy IMI vs. Active control

Table 1. Subgroup and sensitivity analyses

Subgroup		No. of included studies	Pooled SMD^a	95%CI	I^2	Q (df, p)
Control conditions
	IMI vs. TAU	7	−0.27*	−0.51, −0.02	74%	22.82* (6, <0.001)
	IMI vs. Control writing	4	−0.16	−0.53, 0.21	76%	6.71* (3, 0.082)
	IMI vs. Psychoeducation	4	−0.82	−2.21, 0.57	95%	41.55* (2, <0.001)
Therapeutic backgrounds
	IMI (CBT only) vs. Control	6	−0.54*	−0.98, 0.10	92%	60.62* (5, <0.001)
	IMI (writing only) vs. Control	5	−0.26	−0.61, 0.08	74%	15.11* (4, 0.004)
	IMI (training only) vs. Control	5	−0.32	−0.67, 0.03	56%	9.02 (4, 0.06)
Type of symptom severity rating
	IMI vs. Control (self-report measurements only)	17	−0.38*	−0.58, −0.18	86%	111.24* (16, <0.001)
	IMI vs. Control (clinician-administered measurements only)	4	−0.31*	−0.48, −0.14	0%^b	0.95 (3, 0.813)
Adherence
	IMI vs. Control (low dropout only^c)	12	−0.55*	−0.84, −0.26	83%	64.67* (11, <0.001)
Population
	IMI vs. Control (veterans only)	9	−0.27*	−0.51, −0.03	68%	25.29* (8, 0.001)
Sensitivity analyses
	IMI vs. Control (studies with high risk of bias excluded^d)	20	−0.37*	−0.55, −0.22	83%	112.71* (19, <0.001)
	IMI vs. Control (short-term follow-up results^e)	10	−0.39*	−0.67, −0.10	78%	40.48* (9, <0.001)
	IMI vs. Control (medium-term follow-up results^f)	6	−0.20*	−0.38, −0.01	57%	11.57* (5, 0.04)

*Significant SMDs are marked with an asterisk. ^aNegative values characterize effect sizes favouring the intervention group. ^b95%CI 0.0 to 51.8%. ^cStudies with low dropout are defined as ≤20% dropout post-randomization. ^dStudies with high risk of bias are defined as having three or more domains rated with ‘high’. ^eShort-term is defined as up to 3 months or 12 weeks post-randomization. ^fMedium-term is defined as >3 months (or 12 weeks) and <1 year (or 52 weeks) post-randomization.

Table 2. Extent to which mediation studies meet requirements for process research

Author(s) (Year)	RCT	Control	Theoretical background	n ≥ 40 per group	Multiple mediators	Temporality^a	Manipulation
Cieslak et al. (2016)	Yes	Yes	Yes	Yes	No	No	No
Stevens et al. (2017)	Yes	Yes	Yes	Yes	No	No	No
Xu et al. (2016)	Yes	Yes	Yes	Yes	Yes	No	No

^aTemporality is defined as >2 assessments during the treatment phase (including pre- and post-treatment assessment).

Cieslak, R., Benight, C. C., Rogala, A., Smoktunowicz, E., Kowalska, M., Zukowska, K., … Luszczynska, A. (2016). Effects of internet-based self-efficacy intervention on secondary traumatic stress and secondary posttraumatic growth among health and human services professionals exposed to indirect trauma. Frontiers in Psychology, 7, 1009.

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Stevens, N. R., Holmgreen, L., Walt, L., Gengler, R., & Hobfoll, S. E. (2017). Web-based trauma intervention for veterans has physical payoff in randomized controlled trial. Psychological Trauma, 9(1), 42–50.

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Xu, W., Wang, J., Wang, Z., Li, Y., Yu, W., Xie, Q., … Maercker, A. (2016). Web-based intervention improves social acknowledgement and disclosure of trauma, leading to a reduction in posttraumatic stress disorder symptoms. Journal of Health Psychology, 21(11), 2695–2708.

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Data availability statement

The data supporting this systematic review and meta-analysis are from previously reported studies, which have been cited.