Background Cognitive behavioural therapy (CBT) is an evidence-based treatment for anxiety disorders. Many people have difficulty accessing treatment, due to a variety of obstacles. Researchers have therefore explored the possibility of using the Internet to deliver CBT; it is important to ensure the decision to promote such treatment is grounded in high quality evidence. Objectives To assess the effects of therapist-supported Internet CBT on remission of anxiety disorder diagnosis and reduction of anxiety symptoms in adults as compared to waiting list control, unguided CBT, or face-to-face CBT. Effects of treatment on quality of life and patient satisfaction with the intervention were also assessed. Search methods We searched the Cochrane Depression, Anxiety and Neurosis Review Group Specialized Register (CCDANCTR) to 12 April 2013. The CCDANCTR includes relevant randomised controlled trials from EMBASE (1974-), MEDLINE (1950-) and PsycINFO (1967-). We also searched online clinical trial registries and reference lists of included studies. We contacted authors to locate further trials. An update of an initial search (April 2013), conducted in September 2014, identified seven new completed studies, seven previously ongoing studies now completed, and four new ongoing studies. This is a fast-moving area; we plan to update this review shortly, incorporating these new studies. Selection criteria Each identified study was independently assessed for inclusion by two authors. To be included, studies had to be randomised controlled trials of therapist-supported ICBT compared to a waiting list, attention, information, or online discussion group; unguided CBT (that is, self-help); or face-to-face CBT. We included studies that treated adults with an anxiety disorder (panic disorder, agoraphobia, social phobia, post-traumatic stress disorder, acute stress disorder, generalized anxiety disorder, obsessive compulsive disorder, and specific phobia) defined according to the Diagnostic and Statistical Manual of Mental Disorders III, III-R, IV, IV-TR or the International Classification of Disesases 9 or 10. Data collection and analysis Two authors independently assessed the risk of bias of included studies and judged overall study quality. We used data from intention-to-treat analyses wherever possible. We assessed treatment effect for the dichotomous outcome of clinically important improvement in anxiety using a risk ratio (RR) with 95% confidence interval (CI). For disorder-specific and general anxiety symptom measures and quality of life we assessed continuous scores using standardized mean differences (SMD). We examined statistical heterogeneity using the I-2 statistic. Main results We screened 1000 citations and selected 30 studies (2181 participants) for inclusion. The studies examined social phobia (11 trials), panic disorder with or without agoraphobia (8 trials), generalized anxiety disorder (4 trials), post-traumatic stress disorder (1 trial), and specific phobia (1 trial). Five remaining studies included a range of anxiety disorder diagnoses. Studies were conducted in Sweden (15 trials), Australia (12 trials), Switzerland (2 trials), and the Netherlands (1 trial) and investigated a variety of ICBT protocols. Three primary comparisons were identified, experimental versus waiting list control, experimental versus unguided ICBT, and experimental versus face-to-face CBT. Moderate quality evidence from 9 studies (644 participants) contributed to a pooled RR of 4.18 (95% CI 2.42 to 7.22) for clinically important improvement in anxiety at post-treatment, favouring therapist-supported ICBT over a waiting list, attention, information, or online discussion group only. Similarly, the SMD for disorder-specific symptoms at post-treatment (22 studies, 1573 participants; SMD -1.12, 95% CI -1.39 to -0.85) and general anxiety symptoms at post-treatment (14 studies, 1004 participants; SMD -0.79, 95% CI -1.10 to -0.48) favoured therapist-supported ICBT. The quality of the evidence for both outcomes was low. One study compared unguided CBT to therapist-supported ICBT for clinically important improvement in anxiety at post-treatment, showing no difference in outcome between treatments (54 participants; very low quality evidence). At post-treatment there were no clear differences between unguided CBT and therapist-supported ICBT for disorder-specific anxiety symptoms (4 studies, 253 participants; SMD -0.24, 95% CI -0.69 to 0.21; low quality evidence) or general anxiety symptoms (two studies, 138 participants; SMD 0.28, 95% CI -2.21 to 2.78; low quality evidence). Compared to face-to-face CBT, therapist-supported ICBT showed no significant differences in clinically important improvement in anxiety at post-treatment (4 studies, 365 participants; RR 1.09, 95% CI 0.89 to 1.34; moderate quality evidence). There were also no clear differences between face-to-face and therapist supported ICBT for disorder-specific anxiety symptoms at post-treatment (6 studies, 424 participants; SMD 0.09, 95% CI -0.26 to 0.43; low quality evidence) or general anxiety symptoms at post-treatment (5 studies, 317 participants; SMD 0.17, 95% CI -0.35 to 0.69; low quality evidence). Overall, risk of bias in included studies was low or unclear for most domains. However, due to the nature of psychosocial intervention trials, blinding of participants and personnel, and outcome assessment tended to have a high risk of bias. Heterogeneity across a number of the meta-analyses was substantial, some was explained by type of anxiety disorder or may be meta-analytic measurement artefact due to combining many assessment measures. Adverse events were rarely reported. Authors' conclusions Therapist-supported ICBT appears to be an efficacious treatment for anxiety in adults. The evidence comparing therapist-supported ICBT to waiting list, attention, information, or online discussion group only control was low to moderate quality, the evidence comparing therapist-supported ICBT to unguided ICBT was low to very low quality, and comparisons of therapist-supported ICBT to face-to-face CBT was low to moderate quality. Further research is needed to better define and measure any potential harms resulting from treatment. These findings suggest that therapist-supported ICBT is more efficacious than a waiting list, attention, information, or online discussion group only control, and that there may not be a significant difference in outcome between unguided CBT and therapist-supported ICBT; however, this latter finding must be interpreted with caution due to imprecision. The evidence suggests that therapist-supported ICBT may not be significantly different from face-to-face CBT in reducing anxiety. Future research should involve equivalence trials comparing ICBT and face-to-face CBT, examine the importance of the role of the therapist in ICBT, and include effectiveness trials of ICBT in real-world settings. A timely update to this review is needed given the fast pace of this area of research.
