Psychological treatment of panic disorder with or without agoraphobia: a meta-analysis.

Although the efficacy of psychological treatment for panic disorder (PD) with or without agoraphobia has been the subject of a great deal of research, the specific contribution of techniques such as exposure, cognitive therapy, relaxation training and breathing retraining has not yet been clearly established. This paper presents a meta-analysis applying random- and mixed-effects models to a total of 65 comparisons between a treated and a control group, obtained from 42 studies published between 1980 and 2006. The results showed that, after controlling for the methodological quality of the studies and the type of control group, the combination of exposure, relaxation training, and breathing retraining gives the most consistent evidence for treating PD. Other factors that improve the effectiveness of treatments are the inclusion of homework during the intervention and a follow-up program after it has finished. Furthermore, the treatment is more effective when the patients have no comorbid disorders and the shorter the time they have been suffering from the illness. Publication bias and several methodological factors were discarded as a threat against the validity of our results. Finally the implications of the results for clinical practice and for future research are discussed.