The effects of relaxation training on clinical symptoms: a meta-analysis.

Forty-eight experimental studies of nonmechanically assisted relaxation techniques used to control a variety of clinical symptoms were synthesized using meta-analysis. Effect sizes for three types of comparisons, experimental-control, experimental-placebo, and pre-post, ranged from .43 to .66, demonstrating that treatment of any type included in the analysis moved the client from the 50th to the 67th percentile of an untreated group at minimum and from the 50th to the 75th percentile at maximum. All treatments included in the analysis except Benson's relaxation technique demonstrated evidence of effectiveness, particularly for nonsurgical samples with chronic problems such as hypertension, headache, and insomnia.