This pooled analysis evaluated the predictors of clinical outcome in the short-term treatment of panic disorder.

Data were pooled from 4 randomized, placebo-controlled studies of venlafaxine XR in adult outpatients with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) panic disorder with or without agoraphobia (n=1595). Patients were randomly assigned to 10 to 12 weeks' treatment with either placebo or venlafaxine (fixed or flexible dosing, range from 75 mg/d to 225 mg/d). The primary efficacy measure was the proportion of patients free of full-symptom panic attacks at end point. Predictors included panic severity (<8 or ≥8 full-symptom panic attacks during each 2 week period in the 4 weeks prior to baseline) and gender. Other predictors included panic disorder, clinical global impressions, anxiety, somatic and psychic anxiety, depression, mood, phobias, fear, and avoidance.

In both the active treatment and placebo groups, males (65% and 50%, respectively) and those with low symptom severity (69% and 53%, respectively) were significantly (P<0.05) more likely to be panic-free at end point. For nearly all baseline ratings on clinical measures, greater symptom severity was associated with lower proportions of patients who were free from full-symptom panic attacks at end point. Change scores showing improvement in symptom severity following treatment were associated with higher proportions of patients who were free from full-symptom panic attacks at end point.

Panic-free status at end point was predicted by gender, panic disorder severity, and most baseline and change scores of clinical ratings scales.