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NEW YORK (Reuters Health) Jan 23 - Current evidence suggests that for treatment of generalized anxiety disorder (GAD), cognitive behavioral therapy (CBT) is effective, according to a meta-analysis in the Cochrane Database of Systematic Reviews, published online on January 24.

Still, only about half of the patients undergoing CBT in the 25 trials improved significantly, lead author Dr. Vivien Hunot, from the Institute of Psychiatry in London, and her associates report. And the evidence supporting CBT over other psychotherapy was weak.

The UK's National Institute for Health and Clinical Excellence (NICE) recommends CBT as a first-line treatment for GAD. Nevertheless, Dr. Hunot and her associates maintain that in-depth and up-to-date evidence supporting NICE's position is lacking.

According to Dr. Hunot's team, "CBT facilitates the identification of irrational, anxiety-provoking thoughts, and challenges these negative automatic thoughts and dysfunctional underlying beliefs through collaborative 'hypothesis-testing', using...diary-keeping and validity-testing of beliefs between sessions, and skills training within sessions."

The 25 randomized controlled trials included 1305 subjects with a primary diagnosis of GAD. Duration of trials ranged between 4 weeks and 24 months (mean 8 months). Average sample size was 54, ranging from 12 to 119 subjects per trial.

When compared with treatment as usual (13 trials), CBT was more effective in reducing anxiety. CBT also decreased symptoms of worry and depression, and improved social functioning and quality of life.

Only when treatment sessions exceeded eight, did CBT reduce worry, depression, and fear, compared with supportive therapy (6 trials). There was a tendency towards greater response to cognitive therapy than to behavioral therapy in 5 trials, but the differences were small. The one trial of psychodynamic therapy indicated better response to CBT.

Despite their inability to identify strong support for non-CBT approaches for treating GAD, Dr. Hunot's group emphasizes that the "lack of available evidence does not imply that non-CBT approaches are ineffective."

"To enhance the internal validity of future studies" and to increase the applicability of the findings, they recommend larger sample sizes; adequate blinding; longer follow-up; documentation of adherence, adverse effects, quality of life outcomes, and medication use; and estimates of cost-effectiveness.