A team of researchers led by David Baldwin from the University of Southampton have been reviewing trials into drug therapy for generalised anxiety disorder. They reviewed 27 trials comparing nine drugs: duloxetine, escitalopram, fluoxetine, lorazepam, paroxetine, pregabalin, sertraline, tiagabine and venlafaxine. They found that fluoxetine was the most effective and sertraline was the best tolerated i.e. had fewer side effects. Among treatments currently licensed in the UK duloxetine had the best response, escitalopram was ranked first for depression and pregabalin had the fewest side effects.
Baldwin, David ... [et al] - Efficacy of drug treatments for generalised anxiety disorder: systematic review and meta-analysis British Medical Journal BMJ 2011; 342:d1199