ReviewSystematic review and meta-analysis of dropout rates in individual psychotherapy for generalized anxiety disorder
Introduction
Generalized Anxiety Disorder (GAD) consistently falls behind all other anxiety disorders, with the exception of specific phobias, in terms of quantity of research publications (Dugas, Anderson, Deschenes, & Donegan, 2010). This is concerning, given that GAD has a 12-month prevalence of 1.7–3.4% (Wittchen et al., 2011), can have a chronic course with multiple associated psychiatric comorbidities, and is associated with an elevated risk of suicide (Andrews et al., 2010; Wehry, Beesdo-Baum, Hennelly, Connolly, & Strawn, 2015). Yet, GAD is one of the least successfully treated anxiety disorders (Waters & Craske, 2005). Consequently, this diagnosis warrants further treatment research.
Despite these challenges, reviews and practice guidelines have described the established efficacy of pharmacological treatments such as selective serotonin reuptake inhibitors (SSRIs), and psychological treatments such as Cognitive Behavioral Therapy (CBT) for GAD (Allgulander & Baldwin, 2013; Baldwin, Woods, Lawson, & Taylor, 2011; NICE, 2011). In fact, a recent meta-analysis (Cuijpers et al., 2014) of psychological therapies for GAD found a significant overall effect (Hedges g = 0.84), which can be considered a large effect size (Durlak, 2009). This is consistent with a number needed to treat (NNT) of 2.23, indicating that approximately two patients need to be treated with psychological therapy to generate one positive outcome (Cuijpers et al., 2014). A Cochrane review found no significant difference in outcomes between different psychological treatments for GAD (Hunot, Churchill, Silva de Lima, & Teixeira, 2007). There has also been some suggestion that psychotherapy may be preferable to pharmacotherapy due to reduced treatment discontinuation (Mitte, 2005), however there is also evidence that pharmacological treatments are associated with larger effect sizes than psychotherapy for GAD (Bandelow et al., 2015).
Treatment dropout is an important indicator of treatment acceptability and client engagement. Individuals that drop out of therapy tend to have poorer outcomes (Klein, Stone, Hicks, & Pritchard, 2003; McMurran, Huband, & Overton, 2010). Dropout can dilute the benefits of treatment, and interfere with the dissemination of evidence based treatments (Di Bona, Saxon, Barkham, Dent-Brown, & Parry, 2014). Dropout can also influence therapist morale, impact organizations revenue and lead to inefficiencies in service delivery systems (Barrett et al., 2009, Klein et al., 2003, McMurran et al., 2010).
Efforts have been made to develop treatment protocols for GAD aimed at increasing retention (Behar and Borkovec, 2010, Newman et al., 2011; Westra, Antony, & Constantino, 2016). These efforts need to be supported by a clear understanding of the typical dropout rate in psychotherapy for GAD, as well as a specification of what factors are associated with dropout, including characteristics of patients, therapists and treatment modality. Understanding differential dropout rates across GAD treatments can also elucidate whether certain types of treatment pose particularly difficulties in terms of patient engagement. This type of analysis has been conducted in other disorder groups including depression (Cooper & Conklin, 2015), borderline personality disorder (Barnicot, Katsakou, Marougka, & Priebe, 2011) and post-traumatic stress disorder (Imel, Laska, Jakcupcak, & Simpson, 2013) but not with GAD.
The relevant published data addressing dropout in GAD are limited. In their Cochrane Review of outcomes of psychological therapy for GAD, Hunot et al. (2007) found a dropout rate of 15.6%. Yet, this review calculated an overall mean dropout rate rather than a weighted mean that accounts for sample size. Additionally, the analysis was limited to randomized controlled trials and there is evidence that less controlled settings may have higher rates of dropout. For example, one small uncontrolled study of GAD in a community setting found a dropout rate of 72% (Kehle, 2008). Another review of dropout across multiple diagnoses found a similar rate of dropout in GAD of 15.2% (Swift & Greenberg, 2014). That review also included pharmacological treatments and group-based treatments as well as some participants under the age of 18. A focus on individual psychotherapy for adults excluding the potentially confounding effects of medication might yield a more precise estimate of dropout rates in GAD. Furthermore, no study to date has investigated moderators of dropout in GAD.
The present study had two aims. The first was to conduct a systematic review and meta-analysis of the research on individual psychotherapy for GAD and identify a weighted mean dropout rate. The second aim was to determine whether participant, therapist, treatment or study factors might influence dropout rates and account for any heterogeneity across studies in rates of dropout.
Section snippets
Method
This systematic review was conducted in accordance with PRISMA guidelines (Moher et al., 2015).
Results
A summary of the 45 studies included in the meta-analysis is presented in Table 1. There were a total of 2224 participants included in the analysis, with a mean age of 41.62. Studies were predominantly conducted in North America (64%) and Europe (31%), and most were randomized trials (82%). The sample sizes ranged from 8 to 135 and involved majority females (71%), which is consistent with the epidemiology of GAD (Kessler, Petukhova, Sampson, Zaslavsky, & Wittchen, 2012). The modal number of
Discussion
The 16.99% weighted mean dropout rate found in this study suggests that in research studies investigating individual psychological therapy for GAD, approximately one in six clients can be expected to drop out of therapy. This dropout rate is similar to other studies that have examined dropout in treatment for GAD, which have found mean rates in the range of 15.2–15.6% (Hunot et al., 2007, Swift and Greenberg, 2014). A comprehensive review of dropout in adult psychotherapy studies across
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