A Cochrane review included 2 studies with a total of 76 subjects. Both studies, duration ranging from 12 to 18 weeks, were of moderate quality and used active control comparisons (another type of meditation, relaxation, biofeedback). Anti-anxiety drugs were used as standard treatment. In one study transcendental meditation showed a reduction in anxiety symptoms and electromyography score comparable with electromyography-biofeedback and relaxation therapy. Another study compared Kundalini Yoga (KY), with Relaxation/Mindfulness Meditation. The Yale-Brown Obsessive Compulsive Scale showed no statistically significant difference between groups. The overall dropout rate in both studies was high (33-44%). Neither study reported on adverse effects of meditation.
Comment: The quality of evidence is downgraded by limitations in study quality (inadequate standardisation of interventions, high drop-out rates), by imprecise results (few patients and wide confidence intervals), by inconsistency (heterogeneity in interventions and outcomes) and by indirectness (differences in studied interventions).