Characteristics of included studies for meta-analysis.

BDI = Beck Depression Inventory; BSI = Brief Symptom Inventory; CES-D = Center for Epidemiological Studies depression inventory; CFS = chronic fatigue syndrome; Exp. = experimental group; FIQ = Fibromyalgia Impact Questionnaire; FM = fibromyalgia; HADS = Hospital Anxiety and Depression Scale; IBS = irritable bowel syndrome; IBS-GSS = IBS Global Symptom Score; IBS-QoL = IBS Quality of Life Instrument; IBS-SS = IBS Symptom Severity scale; MADRS = Montgomery Asberg Depression Rating Scale; N = number of participants; PCS = Physical Component Summary; S = somatization disorder; SCL-8 = Symptom Checklist; SCL-90-R = Symptom Checklist 90 Revised; SF-36 = SF-36 health survey, STAI = State Trait Anxiety Inventory, Quality of Life subscale; QoL = Quality of Life; VAS = Visual Analogue Scale.