Social anxiety disorder (SAD) has an early onset, follows a chronic course if untreated, leads to functional impairment and is highly prevalent (Kessler et al., 2005a, Kessler et al., 2005b, Wittchen and Fehm, 2003 and Yonkers et al., 2001). The disorder is associated with an increased risk of unemployment and disability pension and the annual societal costs of SAD has been estimated to more than $350 million per one million inhabitants (Acarturk et al., 2009, Bruch et al., 2003, Dahl and Dahl, 2010 and Fehm et al., 2005), which translates to about $111 billion annually in the US. Cognitive behavioral group therapy (CBGT) has been shown to be effective in the treatment of SAD in at least 12 randomized controlled trials (e.g. Blanco et al., 2010 and Heimberg et al., 1990). Access to treatment is however limited (Cavanagh, 2013) and stigma, costs, and difficulty to take time off from work to attend therapy sessions are common barriers to treatment (Mewton et al., 2014 and Moritz et al., 2013). Recently, Internet-based cognitive behavior therapy (ICBT) has emerged as an empirically supported treatment for SAD with effect sizes on par with those of CBGT and tested in at least 16 randomized controlled trials (Berger et al., 2009, Hedman et al., 2012 and Titov et al., 2008). In short, ICBT can be described as online bibliotherapy with therapist support through a secure Internet-based treatment platform (Andersson, 2009). One important advantage of ICBT is that the treatment requires less therapist time, often about 10–15 min weekly per patient (Hedman, Andersson, Ljótsson, Andersson, Ruck, Mortberg, et al., 2011), and is thus a promising means to increase accessibility to effective treatment. In a previously reported randomized non-inferiority trial we found that ICBT for SAD can be at least as effective as CBGT when delivered in a psychiatric setting (Hedman, Andersson, Ljótsson, Andersson, Ruck, Mortberg, et al., 2011). Also, both treatments led to substantial societal indirect cost reductions at 6-month follow-up compared to baseline (Hedman, Andersson, Ljótsson, Andersson, Ruck, & Lindefors, 2011).
Although ICBT for SAD has been tested in many trials only two studies have investigated its long-term effects. These studies demonstrated maintenance of improvement from ICBT up to five years after completed treatment (Carlbring et al., 2009 and Hedman et al., 2011c), which is similar to the long-term effects of CBGT (Heimberg, Salzman, Holt, & Blendell, 1993). However, both studies investigating ICBT lacked control groups. In a study on depression it was found that ICBT was as effective as conventional CBT at three-year follow-up (Andersson et al., 2013), but to our knowledge no study has compared the long-term effects of ICBT for SAD to an active treatment.
When it comes to cost-effectiveness, we have found two studies demonstrating that ICBT is likely to be cost-effective compared to conventional CBT (Hedman et al., 2011a and Titov et al., 2009), but the knowledge on health economic effects of psychological treatment for SAD is scarce. Given the disabling effects of SAD, effectiveness and health economic effects are important to investigate in order to determine long-term societal benefits.
The aim of the present study was to investigate the long-term clinical effectiveness and cost-effectiveness of ICBT vs. CBGT for SAD in a 4-year follow-up study of a randomized controlled non-inferiority trial (Hedman, Andersson, Ljótsson, Andersson, Ruck, Mortberg, et al., 2011). We hypothesized that ICBT would be at least as effective as CBGT in reducing social anxiety and secondary psychiatric symptoms in terms of depression, general anxiety, and anxiety sensitivity. Also, we expected that both treatments would lead to societal cost reductions.
