Abstract: We included 36 studies (33 RCTs) with a total of 3523 participants. Included studies were conducted in sub-Saharan Africa, the Middle East and North Africa, and Asia. Studies were implemented in response to armed conflicts; disasters triggered by natural hazards; and other types of humanitarian crises. Together, the 33 RCTs compared eight psychological treatments against a control comparator. Four studies included children and adolescents between 5 and 18 years of age. Three studies included mixed populations (two studies included participants between 12 and 25 years of age, and one study included participants between 16 and 65 years of age). Remaining studies included adult populations (18 years of age or older). Included trials compared a psychological therapy versus a control intervention (wait list in most studies; no treatment; treatment as usual). Psychological therapies were categorised mainly as cognitive-behavioural therapy (CBT) in 23 comparisons (including seven comparisons focused on narrative exposure therapy (NET), two focused on common elements treatment approach (CETA), and one focused on brief behavioural activation treatment (BA)); eye movement desensitisation and reprocessing (EMDR) in two comparisons; interpersonal psychotherapy (IPT) in three comparisons; thought field therapy (TFT) in three comparisons; and trauma or general supportive counselling in two comparisons. Although interventions were described under these categories, several psychotherapeutic elements were common to a range of therapies (i.e. psychoeducation, coping skills). In adults, psychological therapies may substantially reduce endpoint PTSD symptoms compared to control conditions (standardised mean difference (SMD) -1.07, 95% confidence interval (CI) -1.34 to -0.79; 1272 participants; 16 studies; low-quality evidence). The effect is smaller at one to four months (SMD -0.49, 95% CI -0.68 to -0.31; 1660 participants; 18 studies) and at six months (SMD -0.37, 95% CI -0.61 to -0.14; 400 participants; five studies). Psychological therapies may also substantially reduce endpoint depression symptoms compared to control conditions (SMD -0.86, 95% CI -1.06 to -0.67; 1254 participants; 14 studies; low-quality evidence). Similar to PTSD symptoms, follow-up data at one to four months showed a smaller effect on depression (SMD -0.42, 95% CI -0.63 to -0.21; 1386 participants; 16 studies). Psychological therapies may moderately reduce anxiety at endpoint (SMD -0.74, 95% CI -0.98 to -0.49; 694 participants; five studies; low-quality evidence) and at one to four months' follow-up after treatment (SMD -0.53, 95% CI -0.66 to -0.39; 969 participants; seven studies). Dropout rates are probably similar between study conditions (19.5% with control versus 19.1% with psychological therapy (RR 0.98 95% CI 0.82 to 1.16; 2930 participants; 23 studies, moderate quality evidence)). In children and adolescents, we found very low quality evidence for lower endpoint PTSD symptoms scores in psychotherapy conditions (CBT) compared to control conditions, although the confidence interval is wide (SMD -1.56, 95% CI -3.13 to 0.01; 130 participants; three studies;). No RCTs provided data on major depression or anxiety in children. The effect on withdrawal was uncertain (RR 1.87 95% CI 0.47 to 7.47; 138 participants; 3 studies, low quality evidence). We did not identify any studies that evaluated psychological treatments on (symptoms of) somatoform disorders or MUPS in LMIC humanitarian settings. There is low quality evidence that psychological therapies have large or moderate effects in reducing PTSD, depressive, and anxiety symptoms in adults living in humanitarian settings in LMICs. By one to four month and six month follow-up assessments treatment effects were smaller. Fewer trials were focused on children and adolescents and they provide very low quality evidence of a beneficial effect of psychological therapies in reducing PTSD symptoms at endpoint. Confidence in these findings is influenced by the risk of bias in the studies and by substantial levels of heterogeneity. More research evidence is needed, particularly for children and adolescents over longer periods of follow-up.

Plain-language summary: In adults, low-quality evidence shows greater benefit from psychological therapies than from control comparators in reducing (symptoms of) PTSD, major depression, and anxiety disorders. This evidence supports the approach of providing psychological therapies to populations affected by humanitarian crises, although we identified no studies that looked at the effectiveness or acceptability of psychological therapies for depressive and anxiety symptoms beyond six months. Only a small proportion of included trials reported data on children and adolescents, which provided very low-quality evidence of greater benefit derived from psychological treatments. With regard to acceptability, moderate- to low-quality evidence suggests no differences in dropout rates among adults and children and adolescents. Reviewers found no studies evaluating psychological treatments for (symptoms of) somatoform disorders or medically unexplained physical symptoms (MUPS) in adults, nor in children or adolescents, respectively. Researchers should conduct higher-quality trials to further evaluate the effectiveness of psychological therapies provided over longer periods to adults and to children and adolescents. Ideally, trials should be randomised, should use culturally appropriate and validated instruments to evaluate outcomes, and should assess correlates of reductions in treatment effects over time; in addition, researchers should make every effort to ensure high rates of follow-up beyond six months after completion of therapy.