Exposure versus Cognitive Therapy in Anxiety Disorders
Exposure versus Cognitive Therapy in Anxiety Disorders
The initial search revealed a total of 1,612 articles. Having applied the exclusion criteria and having removed the duplicates this was reduced to 61 full text articles assessed for eligibility. None of the 61 articles were in a language other than English. There were disagreements about including 5 articles. Following a consensus meeting 20 RCTs were included in the final quantitative synthesis (additional file 1, PRISMA flowchart). The main reason for exclusion was unclear distinction between exposure and cognitive therapy. In particular the studies that did not have a clear focus on cognitive change were excluded from the CT group and the studies that did not have a clear focus on habituation were excluded from the E condition. The trials were grouped according to the condition studied: Obsessive Compulsive Disorder (OCD), Post-Traumatic Stress Disorder (PTSD), Panic Disorder with or without agoraphobia (PD) and Social Phobia (SP). Assessor blinding was adequate (or a self-reported tool was used as the main outcome measure) in 11 studies and uncertain in nine studies. Six countries were represented in the included studies: Canada, France, the UK, USA and the Netherlands. Together, the studies enrolled a total of N = 1,308 patients. Of those 1,044 were allocated to either CT or E condition and the rest were allocated to a comparison treatment or control conditions.
Studies of Cognitive Therapy versus Exposure in Obsessive Compulsive Disorder Five studies have met the criteria for inclusion in this meta-analysis. Their results were reported in six articles (Table S1, additional file 2). All included studies reported the pre- and post-treatment values for Yale-Brown Obsessive Compulsive Scale (Y-BOCS). This is a semi-structured clinician-administered interview providing a score (range –40) for both obsessions (range –20) and compulsions (range –20) along five dimensions: time spent, interference, distress, resistance, and control. One of the studies contained a condition of E + fluvoxamine and CT + fluvoxamine. These two conditions were excluded due to drop out rates exceeding 30% (36% and 41% respectively); however the pure E and CT groups were included in the review and the meta-analysis. The studies comparing Rational Emotive Therapy (RET) with Exposure were excluded as the RET model lacks theoretical coherence and empirical evidence afforded by the modern cognitive behaviour models.
Studies of Cognitive Therapy versus Exposure in Post Traumatic Stress Disorder Five studies met the criteria for inclusion in this meta-analysis (Table S2, additional file 3). Three of the included studies reported the pre- and post-treatment values for Clinician-Administered PTSD scale (CAPS). CAPS has 30 items, assessor-rated, rating frequency and intensity of the 17 PTSD symptoms and 8 associated features of PTSD (built over acts of commission or omission, survivor guilt, homicidality, disillusionment with authority, hopelessness, memory impairment and forgetfulness, sadness and depression and feeling overwhelmed). Each item is rated –4 for intensity and frequency. One study used an aggregate PTSD severity index calculated by adding the interviewer's severity rating of the following PTSD symptoms: reliving experiences, nightmares, flashbacks, avoidance of reminders and thoughts of the assault, impaired leisure activities (e.g., reduced socializing), sense of detachment, blunted affect, disturbed sleep, memory and concentration difficulties, hyperalertness, increased startle response, feelings of guilt, and increased fearfulness. One study used PTSD Symptom Scale - Interview (PSS-I) The scale contains 17 items that diagnose PTSD according to Diagnostic and Statistical Manual of Mental Disorders-III-Revised (DSM-III-R) criteria and assess the severity of PTSD symptoms.
Studies of Cognitive Therapy versus Exposure in Panic Disorder With or Without Agoraphobia Seven studies met the criteria for inclusion in this meta-analysis (Table S3, additional file 4). Six included studies reported the pre- and post-treatment values for the proportion of the patients free from panic attacks based on self-report. One study only gave the raw number of reported panic attacks; however the proportion of the patients free from panic attack was calculated on the basis of the data provided.
Studies of Cognitive Therapy versus Exposure in Social Phobia Three studies met the inclusion criteria for this meta-analysis (Table S4, additional file 5). Two studies used a social phobia composite score as the main outcome measure and one study used Social Phobia and Anxiety Inventory (SPAI) as the main outcome measure. The SPAI is a 109-item self-report instrument that has been widely used to assess the cognitive, somatic and behavioural dimensions of social phobia. One of the studies used a comparison between Cognitive Therapy and Exposure with Fluoxetine or Exposure with Placebo. The arm including Fluoxetine treatment was excluded as per inclusion criteria.
Meta-analysis of Cognitive Therapy versus Exposure Efficacy in Obsessive Compulsive Disorder
Short-term Outcomes Five studies reported short-term efficacy (the end of treatment mean Y-BOCS score) of CT versus E in 290 patients (Table 1). The overall effect is summarised in Figure 1. There was no statistically significant difference between the two conditions. Fixed-effects model was used to estimate the overall effect as there was no evidence of significant heterogeneity (I = 49%).
(Enlarge Image)
Figure 1.
Cognitive therapy versus exposure for OCD. Meta-analysis: short-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance; OCD = Obsessive Compulsive Disorder.
Long-term Outcomes Four studies reported long-term efficacy (the mean Y-BOCS score at the point of the longest reported follow up) of CT versus E in 181 patients (Table 1). The overall effect is summarised in Figure 2. There was no statistically significant difference between the two conditions. Random-effects model was used to estimate the overall effect as there was evidence of significant heterogeneity (I = 51%).
(Enlarge Image)
Figure 2.
Cognitive therapy versus exposure for OCD. Meta-analysis: long-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance; OCD = Obsessive Compulsive Disorder.
Short-term Outcomes Five studies reported short-term efficacy of CT versus E in 287 patients (Table 2). The overall effect (the end-of-treatment standardized mean differences, Hedge's g) is summarised in Figure 3. There was no statistically significant difference between the two conditions. Fixed-effects model was used to estimate the overall effect as there was no evidence of significant heterogeneity (I = 29%).
(Enlarge Image)
Figure 3.
Cognitive therapy versus exposure for PTSD. Meta-analysis: short-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance; PTSD = Post Traumatic Stress Disorder.
Long-term Outcomes Four studies reported long-term efficacy reported long-term efficacy of CT versus E in 226 patients (Table 2). The overall effect (the standardized means differences, Hedge's g at the longest-reported follow up) is summarised in Figure 4. There was no statistically significant difference between the two conditions. Fixed-effects model was used to estimate the overall effect as there was no evidence of significant heterogeneity (I = 0).
(Enlarge Image)
Figure 4.
Cognitive therapy versus exposure for PTSD. Meta-analysis: long-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance; PTSD = Post Traumatic Stress Disorder.
Short-term Outcomes Seven studies reported short-term efficacy (the end of treatment proportion of panic-free patients) of CT versus E in 274 patients ( Table 3 ). The overall effect is summarised in Figure 5. There was no statistically significant difference between the two conditions. Random-effects model was used to estimate the overall effect as there was evidence of significant heterogeneity (I = 68%).
(Enlarge Image)
Figure 5.
Cognitive therapy versus exposure for panic disorder. Meta-analysis: short-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance.
Long-term Outcomes Six studies reported long-term efficacy (the end of treatment proportion of panic-free patients) of CT versus E in 247 patients ( Table 3 ). The overall effect is summarised in Figure 6. There was no statistically significant difference between the two conditions. Fixed-effects model was used to estimate the overall effect as there was no evidence of significant heterogeneity (I = 24%).
(Enlarge Image)
Figure 6.
Cognitive therapy versus exposure for panic disorder. Meta-analysis: long-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance.
Short-term Outcomes Three studies reported short-term efficacy of CT versus E in 128 patients ( Table 4 ). The overall effect (the end-of-treatment standardised means differences, Hedge's g) is summarised in Figure 7. There was a statistically significant difference favouring CT versus E. Fixed-effects model was used to estimate the overall effect as there was no evidence of significant heterogeneity (I = 45%).
(Enlarge Image)
Figure 7.
Cognitive therapy versus exposure for social phobia. Meta-analysis: short-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance.
Long-term Outcomes Two studies totalling 75 patients reported long-term efficacy (the standardised means differences, Hedge's g, at the longest-reported follow up) of CT versus E ( Table 4 ). The overall effect is summarised in Figure 8. There was a statistically significant difference favouring CT versus E. Fixed-effects model was used to estimate the overall effect as there was no evidence of significant heterogeneity (I = 0)
(Enlarge Image)
Figure 8.
Cognitive therapy versus exposure for social phobia. Meta-analysis: long-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance.
Publication Bias Condition-specific funnel plots did not indicate publication bias. Small number of studies in each comparison, however, means that the assessment of publication bias needs to be interpreted with caution.
Other Anxiety Disorders There are studies examining relative efficacy of exposure and cognitive therapy in other anxiety disorders: hypochondriasis and generalised anxiety disorder (GAD). More studies are needed before a summary effect of CT versus E could be estimated in these conditions.
Results
Selection Results
The initial search revealed a total of 1,612 articles. Having applied the exclusion criteria and having removed the duplicates this was reduced to 61 full text articles assessed for eligibility. None of the 61 articles were in a language other than English. There were disagreements about including 5 articles. Following a consensus meeting 20 RCTs were included in the final quantitative synthesis (additional file 1, PRISMA flowchart). The main reason for exclusion was unclear distinction between exposure and cognitive therapy. In particular the studies that did not have a clear focus on cognitive change were excluded from the CT group and the studies that did not have a clear focus on habituation were excluded from the E condition. The trials were grouped according to the condition studied: Obsessive Compulsive Disorder (OCD), Post-Traumatic Stress Disorder (PTSD), Panic Disorder with or without agoraphobia (PD) and Social Phobia (SP). Assessor blinding was adequate (or a self-reported tool was used as the main outcome measure) in 11 studies and uncertain in nine studies. Six countries were represented in the included studies: Canada, France, the UK, USA and the Netherlands. Together, the studies enrolled a total of N = 1,308 patients. Of those 1,044 were allocated to either CT or E condition and the rest were allocated to a comparison treatment or control conditions.
General Study Characteristics
Studies of Cognitive Therapy versus Exposure in Obsessive Compulsive Disorder Five studies have met the criteria for inclusion in this meta-analysis. Their results were reported in six articles (Table S1, additional file 2). All included studies reported the pre- and post-treatment values for Yale-Brown Obsessive Compulsive Scale (Y-BOCS). This is a semi-structured clinician-administered interview providing a score (range –40) for both obsessions (range –20) and compulsions (range –20) along five dimensions: time spent, interference, distress, resistance, and control. One of the studies contained a condition of E + fluvoxamine and CT + fluvoxamine. These two conditions were excluded due to drop out rates exceeding 30% (36% and 41% respectively); however the pure E and CT groups were included in the review and the meta-analysis. The studies comparing Rational Emotive Therapy (RET) with Exposure were excluded as the RET model lacks theoretical coherence and empirical evidence afforded by the modern cognitive behaviour models.
Studies of Cognitive Therapy versus Exposure in Post Traumatic Stress Disorder Five studies met the criteria for inclusion in this meta-analysis (Table S2, additional file 3). Three of the included studies reported the pre- and post-treatment values for Clinician-Administered PTSD scale (CAPS). CAPS has 30 items, assessor-rated, rating frequency and intensity of the 17 PTSD symptoms and 8 associated features of PTSD (built over acts of commission or omission, survivor guilt, homicidality, disillusionment with authority, hopelessness, memory impairment and forgetfulness, sadness and depression and feeling overwhelmed). Each item is rated –4 for intensity and frequency. One study used an aggregate PTSD severity index calculated by adding the interviewer's severity rating of the following PTSD symptoms: reliving experiences, nightmares, flashbacks, avoidance of reminders and thoughts of the assault, impaired leisure activities (e.g., reduced socializing), sense of detachment, blunted affect, disturbed sleep, memory and concentration difficulties, hyperalertness, increased startle response, feelings of guilt, and increased fearfulness. One study used PTSD Symptom Scale - Interview (PSS-I) The scale contains 17 items that diagnose PTSD according to Diagnostic and Statistical Manual of Mental Disorders-III-Revised (DSM-III-R) criteria and assess the severity of PTSD symptoms.
Studies of Cognitive Therapy versus Exposure in Panic Disorder With or Without Agoraphobia Seven studies met the criteria for inclusion in this meta-analysis (Table S3, additional file 4). Six included studies reported the pre- and post-treatment values for the proportion of the patients free from panic attacks based on self-report. One study only gave the raw number of reported panic attacks; however the proportion of the patients free from panic attack was calculated on the basis of the data provided.
Studies of Cognitive Therapy versus Exposure in Social Phobia Three studies met the inclusion criteria for this meta-analysis (Table S4, additional file 5). Two studies used a social phobia composite score as the main outcome measure and one study used Social Phobia and Anxiety Inventory (SPAI) as the main outcome measure. The SPAI is a 109-item self-report instrument that has been widely used to assess the cognitive, somatic and behavioural dimensions of social phobia. One of the studies used a comparison between Cognitive Therapy and Exposure with Fluoxetine or Exposure with Placebo. The arm including Fluoxetine treatment was excluded as per inclusion criteria.
Meta-analyses
Meta-analysis of Cognitive Therapy versus Exposure Efficacy in Obsessive Compulsive Disorder
Short-term Outcomes Five studies reported short-term efficacy (the end of treatment mean Y-BOCS score) of CT versus E in 290 patients (Table 1). The overall effect is summarised in Figure 1. There was no statistically significant difference between the two conditions. Fixed-effects model was used to estimate the overall effect as there was no evidence of significant heterogeneity (I = 49%).
(Enlarge Image)
Figure 1.
Cognitive therapy versus exposure for OCD. Meta-analysis: short-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance; OCD = Obsessive Compulsive Disorder.
Long-term Outcomes Four studies reported long-term efficacy (the mean Y-BOCS score at the point of the longest reported follow up) of CT versus E in 181 patients (Table 1). The overall effect is summarised in Figure 2. There was no statistically significant difference between the two conditions. Random-effects model was used to estimate the overall effect as there was evidence of significant heterogeneity (I = 51%).
(Enlarge Image)
Figure 2.
Cognitive therapy versus exposure for OCD. Meta-analysis: long-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance; OCD = Obsessive Compulsive Disorder.
Meta-analysis of Cognitive Therapy versus Exposure Efficacy in Post Traumatic Stress Disorder
Short-term Outcomes Five studies reported short-term efficacy of CT versus E in 287 patients (Table 2). The overall effect (the end-of-treatment standardized mean differences, Hedge's g) is summarised in Figure 3. There was no statistically significant difference between the two conditions. Fixed-effects model was used to estimate the overall effect as there was no evidence of significant heterogeneity (I = 29%).
(Enlarge Image)
Figure 3.
Cognitive therapy versus exposure for PTSD. Meta-analysis: short-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance; PTSD = Post Traumatic Stress Disorder.
Long-term Outcomes Four studies reported long-term efficacy reported long-term efficacy of CT versus E in 226 patients (Table 2). The overall effect (the standardized means differences, Hedge's g at the longest-reported follow up) is summarised in Figure 4. There was no statistically significant difference between the two conditions. Fixed-effects model was used to estimate the overall effect as there was no evidence of significant heterogeneity (I = 0).
(Enlarge Image)
Figure 4.
Cognitive therapy versus exposure for PTSD. Meta-analysis: long-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance; PTSD = Post Traumatic Stress Disorder.
Meta-analysis of Cognitive Therapy versus Exposure Efficacy in Panic Disorder With or Without Agoraphobia
Short-term Outcomes Seven studies reported short-term efficacy (the end of treatment proportion of panic-free patients) of CT versus E in 274 patients ( Table 3 ). The overall effect is summarised in Figure 5. There was no statistically significant difference between the two conditions. Random-effects model was used to estimate the overall effect as there was evidence of significant heterogeneity (I = 68%).
(Enlarge Image)
Figure 5.
Cognitive therapy versus exposure for panic disorder. Meta-analysis: short-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance.
Long-term Outcomes Six studies reported long-term efficacy (the end of treatment proportion of panic-free patients) of CT versus E in 247 patients ( Table 3 ). The overall effect is summarised in Figure 6. There was no statistically significant difference between the two conditions. Fixed-effects model was used to estimate the overall effect as there was no evidence of significant heterogeneity (I = 24%).
(Enlarge Image)
Figure 6.
Cognitive therapy versus exposure for panic disorder. Meta-analysis: long-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance.
Meta-analysis of Cognitive Therapy Efficacy versus Exposure in Social Phobia
Short-term Outcomes Three studies reported short-term efficacy of CT versus E in 128 patients ( Table 4 ). The overall effect (the end-of-treatment standardised means differences, Hedge's g) is summarised in Figure 7. There was a statistically significant difference favouring CT versus E. Fixed-effects model was used to estimate the overall effect as there was no evidence of significant heterogeneity (I = 45%).
(Enlarge Image)
Figure 7.
Cognitive therapy versus exposure for social phobia. Meta-analysis: short-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance.
Long-term Outcomes Two studies totalling 75 patients reported long-term efficacy (the standardised means differences, Hedge's g, at the longest-reported follow up) of CT versus E ( Table 4 ). The overall effect is summarised in Figure 8. There was a statistically significant difference favouring CT versus E. Fixed-effects model was used to estimate the overall effect as there was no evidence of significant heterogeneity (I = 0)
(Enlarge Image)
Figure 8.
Cognitive therapy versus exposure for social phobia. Meta-analysis: long-term outcomes Note. SD = Standard Deviation; IV = Inverse Variance.
Publication Bias Condition-specific funnel plots did not indicate publication bias. Small number of studies in each comparison, however, means that the assessment of publication bias needs to be interpreted with caution.
Other Anxiety Disorders There are studies examining relative efficacy of exposure and cognitive therapy in other anxiety disorders: hypochondriasis and generalised anxiety disorder (GAD). More studies are needed before a summary effect of CT versus E could be estimated in these conditions.
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