[Which distinguishing features characterize self-help groups? A grid for description and research].

There is limited evidence on the effectiveness of self-help groups. One research barrier is their heterogeneity. For this reason, characteristics of self-help groups were extracted by means of a conceptual review from three relevant fields of knowledge (outcome studies, health care supply research, practical experiences in implementing self-help groups). As a structure for the characteristics, QIP ("Quality in Prevention", an evidence-based quality assurance system for the assessment of health promotion and education) was used. The resulting taxonomy of 91 characteristics includes all distinguishing marks of self-help groups which, according to the evidence, may contribute to the groups' effectiveness. The methodological quality of evidence, however, was low (mostly expert-based opinion). The taxonomy may assist in systematic analyses of structural, procedural and outcome-quality, for example in evaluations or in health care supply studies.