Background Therapist-delivered trauma-focused psychological therapies are an effective treatment for post-traumatic stress disorder (PTSD). These have become the accepted first-line treatments for the disorder. Despite the established evidence-base for these therapies, they are not always widely available or accessible. Many barriers limit treatment uptake, such as the limited number of qualified therapists to deliver the interventions, cost, and compliance issues, such as time off work, childcare, and transportation, associated with the need to attend weekly appointments. Delivering cognitive behavioural therapy (CBT) on the Internet is an effective and acceptable alternative to therapist-delivered treatments for anxiety and depression. However, fewer Internet-based therapies have been developed and evaluated for PTSD, and uncertainty surrounds the efficacy of Internet-based cognitive and behavioural therapy (I-C/BT) for PTSD. Objectives To assess the effects of I-C/BT for PTSD in adults. Search methods We searched the Cochrane Common Mental Disorders Group's Specialised Register (CCMDCTR) to June 2016 and identified four studies meeting the inclusion criteria. The CCMDCTR includes relevant randomised controlled trials (RCT) from MEDLINE, Embase, and PsycINFO. We also searched online clinical trial registries and reference lists of included studies, and contacted researchers in the field to identify additional and ongoing studies. We ran an update search on 1 March 2018, and identified four additional completed studies, which we added to the analyses along with two that were previously awaiting classification. Selection criteria We searched for RCTs of I-C/BT compared to face-to-face or Internet-based psychological treatment, psychoeducation, wait list or care as usual. We included studies of adults (aged over 16 years or over), in which at least 70% of the participants met the diagnostic criteria for PTSD, according to the Diagnostic and Statistical Manual (DSM) or the International Classification of Diseases (ICD). Data collection and analysis We entered data into Review Manager 5 software. We analysed categorical outcomes as risk ratios (RRs), and continuous outcomes as mean differences (MD) or standardised mean differences (SMDs), with 95% confidence intervals (CI). We pooled data with a fixed-effect meta-analysis, except where heterogeneity was present, in which case we used a random-effects model. Two review authors independently assessed the included studies for risk of bias; any conflicts were discussed with a third author, with the aim of reaching a unanimous decision. Main results We included 10 studies with 720 participants in the review. Eight of the studies compared I-C/BT delivered with therapist guidance to a wait list control. Two studies compared guided I-C/BT with I-non-C/BT. There was considerable heterogeneity among the included studies. Very low-quality evidence showed that, compared with wait list, I-C/BT may be associated with a clinically important reduction in PTSD post-treatment (SMD -0.60, 95% CI -0.97 to -0.24; studies = 8, participants = 560). However, there was no evidence of a difference in PTSD symptoms when follow-up was less than six months (SMD -0.43, 95% CI -1.41 to 0.56; studies = 3, participants = 146). There may be little or no difference in dropout rates between the I-C/BT and wait list groups (RR 1.39, 95% CI 1.03 to 1.88; studies = 8, participants = 585; low-quality evidence). I-C/BT was no more effective than wait list at reducing the risk of a diagnosis of PTSD after treatment (RR 0.53, 95% CI 0.28 to 1.00; studies = 1, participants = 62; very low-quality evidence). I-C/BT may be associated with a clinically important reduction in symptoms of depression both post-treatment (SMD -0.61, 95% CI -1.17 to -0.05; studies = 5, participants = 425; very low-quality evidence). Very low-quality evidence also suggested that I-C/BTmay be associated with a clinically important reduction in symptoms of anxiety post-treatment (SMD -0.67, 95% CI -0.98 to -0.36; studies = 4, participants = 305), and at follow-up less than six months (MD -12.59, 95% CI -20.74 to -4.44; studies = 1, participants = 42; very low-quality evidence). The effects of I-C/BT on quality of life were uncertain (SMD 0.60, 95% CI 0.08 to 1.12; studies = 2, participants = 221; very low-quality evidence). Two studies found no difference in PTSD symptoms between the I-C/BT and I-non-C/BT groups when measured post-treatment (SMD -0.08, 95% CI -0.52 to 0.35; studies = 2, participants = 82; very low-quality evidence), or when follow-up was less than six months (SMD 0.08, 95% CI -0.41 to 0.57; studies = 2, participants = 65; very low-quality evidence). However, those who received I-C/BT reported their PTSD symptoms were better at six-to 12-month follow-up (MD -8.83, 95% CI -17.32 to -0.34; studies = 1, participants = 18; very low-quality evidence). Two studies found no difference in depressive symptoms between the I-C/BT and Inon- C/BT groups when measured post-treatment (SMD -0.12, 95% CI -0.78 to 0.54; studies = 2, participants = 84; very low-quality evidence) or when follow-up was less than six months (SMD 0.20, 95% CI -0.31 to 0.71; studies = 2, participants = 61; very lowquality evidence). However, those who received I-C/BT reported their depressive symptoms were better at six-to 12-month followup (MD -8.34, 95% CI -15.83 to -0.85; studies = 1, participants = 18; very low-quality evidence). Two studies found no difference in symptoms of anxiety between the I-C/BT and I-non-C/BT groups when measured post-treatment (SMD 0.08, 95% CI -0.78 to 0.95; studies = 2, participants = 74; very low-quality evidence) or when follow-up was less than six months (SMD -0.16, 95% CI -0.67 to 0.35; studies = 2, participants = 60; very low-quality evidence). However, those who received I-C/BT reported their symptoms of anxiety were better at six-to 12-month follow-up (MD -8.05, 95% CI -15.20 to -0.90; studies = 1, participants = 18; very low-quality evidence). None of the included studies reported on cost-effectiveness or adverse events.
