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.