Cognitive behavioral therapy for anxiety and related disorders: A meta-analysis of randomized placebo-controlled trials

Abstract

The purpose of this study was to examine the efficacy of cognitive behavioral therapy (CBT) for anxiety-related disorders based on randomized placebo-controlled trials. We included 41 studies that randomly assigned patients (N = 2,843) with acute stress disorder, generalized anxiety disorder (GAD), obsessive compulsive disorder (OCD), panic disorder (PD), posttraumatic stress disorder (PTSD), or social anxiety disorder (SAD) to CBT or a psychological or pill placebo condition. Findings demonstrated moderate placebo-controlled effects of CBT on target disorder symptoms (Hedges' g = 0.56), and small to moderate effects on other anxiety symptoms (Hedges' g = 0.38), depression (Hedges' g = 0.31), and quality of life (Hedges' g = 0.30). Response rates in CBT compared to placebo were associated with an odds ratio of 2.97. Effects on the target disorder were significantly stronger for completer samples than intent-to-treat samples, and for individuals compared to group CBT in SAD and PTSD studies. Large effect sizes were found for OCD, GAD, and acute stress disorder, and small to moderate effect sizes were found for PTSD, SAD, and PD. In PTSD studies, dropout rates were greater in CBT (29.0%) compared to placebo (17.2%), but no difference in dropout was found across other disorders. Interventions primarily using exposure strategies had larger effect sizes than those using cognitive or cognitive and behavioral techniques, though this difference did not reach significance. Findings demonstrate that CBT is a moderately efficacious treatment for anxiety disorders when compared to placebo. More effective treatments are especially needed for PTSD, SAD, and PD.

Keywords: anxiety; anxiety disorders; behavior therapy; cognitive therapy; meta-analysis; treatment outcome.

Figure 1

Flow diagram of study selection process

Figure 2

Effect size estimates (Hedges’ g) and 95% confidence intervals (CI) for acute efficacy of CBT relative to placebo on diagnosis-specific symptom measures. ASD = Acute Stress Disorder; GAD = Generalized Anxiety Disorder; OCD = Obsessive- Compulsive Disorder; PD = Panic Disorder; PTSD = Post Traumatic Stress Disorder; SAD = Social Anxiety Disorder.

Figure 3

Odds ratios (OR) and 95% confidence intervals (CI) for responder status following acute CBT compared to placebo. ASD = Acute Stress Disorder; GAD = Generalized Anxiety Disorder; OCD = Obsessive- Compulsive Disorder; PD = Panic Disorder; PTSD = Post Traumatic Stress Disorder; SAD = Social Anxiety Disorder. CIDI = Composite International Diagnostic Interview PTSD Module; CAPS = Clinician Administered PTSD Scale; CGI - S = Clinical Global Impressions Scale – Severity; CGI - I = Clinical Global Impressions Scale – Improvement; SRT = Symptom Rating Test; CSC = Clinically Significant Change (See Sharp et al., 1996, Foa et al., 1991, or Lucas, 1994); PCLS = PTSD Checklist; SRQ-20 = Self-Reporting Questionnaire; SPDS-S = Social Phobic Disorder Severity; SPDS-C = Social Phobic Disorder Change Form; FNE = Fear of Negative Evaluation Scale; SIAS = Social Interaction Anxiety Scale; CIC-SP = Clinical Impression of Change — Social Phobia Scale; LSAS-SR = Liebowitz Social Anxiety Scale.

Figure 4

Placebo-controlled effect sizes and 95% confidence intervals (CI) for disorder-specific, anxiety, depression and quality of life measures QOL = Quality of Life. ASD = Acute Stress Disorder; GAD = Generalized Anxiety Disorder; OCD = Obsessive- Compulsive Disorder; PD = Panic Disorder; PTSD = Post Traumatic Stress Disorder; SAD = Social Anxiety Disorder.

Figure 5

Odds ratios and 95% confidence intervals (CI) of treatment response for CBT compared by target disorder QOL = Quality of Life. ASD = Acute Stress Disorder; GAD = Generalized Anxiety Disorder; OCD = Obsessive- Compulsive Disorder; PD = Panic Disorder; PTSD = Post Traumatic Stress Disorder; SAD = Social Anxiety Disorder.