Background: A subset of patients with comorbid major depressive disorder and generalized anxiety disorder (GAD) was examined from a double-blind. placebo-controlled study comparing the efficacy and safety of venlafaxine extended release (XR) and fluoxetine.
Method: From a total of 368 patients, 92 patients meeting DSM-IV criteria for major depressive disorder who also had comorbid GAD were identified. The comparison group comprised 276 evaluable noncomorbid patients. Patients received venlafaxine XR (75-225 mg/day), fluoxetine (20-60 mg/day), or placebo for 12 weeks. Efficacy evaluations included Hamilton Rating Scale for Depression (HAM-D), Hamilton Rating Scale for Anxiety (HAM-A), and Clinical Global Impressions (CGI) scale.
Results: By the final assessment at week 12, comorbid patients in the venlafaxine XR group, but not in the fluoxetine group, showed a significantly greater decrease than those in the placebo group in the primary efficacy variables of mean HAM-D and HAM-A total scores (p < .05, pairwise comparison). In comorbid patients, significant pairwise differences were noted between venlafaxine XR and placebo at week 12 for the secondary variables of HAM-D anxiety-somatization and retardation factors, HAM-D depressed mood item. HAM-A psychic anxiety factor, the Hospital Anxiety and Depression scale (HAD) anxiety subscale score, and the Covi Anxiety Scale score. Fluoxetine was significantly different from placebo only on the HAD depression subscale score. Response, defined as > or = 50% decrease in symptoms score, was achieved in 66% and 59% of the comorbid patients for HAM-D and HAM-A, respectively, in the venlafaxine XR group at week 12. This response was higher than that seen with fluoxetine (52% and 45%) or placebo (36% and 24%). Onset of efficacy appeared to be slower in comorbid than in noncomorbid patients.
Conclusion: This is the first evidence from a controlled study of the effectiveness of pharmacotherapy in patients with comorbid major depressive disorder and GAD. The delayed improvement in comorbid patients compared with noncomorbid patients suggests that a longer treatment period may be necessary in comorbid patients.