Critical appraisal of clinical studies and meta-analyses - An educational article on the most important validity criteria according to Evidence-based Medicine (EbM)

The Oxford Dictionary of Current English defines ,,evidence" as,available facts, circumstances, etc. indicating whether a thing is true or not true." In conjunction with clinical expertise, which can just be acquired by clinical practice, evidence-based medicine (EbM) is considered as a lifelong learning process which is targeted on adjustment on fast varying medical knowledge by continuous problem-focused learning. Thus, there is an increasing need for medical education due to the systematic assessment of clinical studies by mental health care specialists. The associated methodology has been developed in the eighties by the Cochrane Collaboration in Oxford, whose intention is to compile systematic reviews regarding assessment of therapies as well as to update and publish them. The critical appraisal of clinical studies and meta-analyses is based on validity criteria with regard to study design, biostatistics, study population and interpretation according to Sackett et al., and will be summarized. According to the methods of evidence-based medicine the estimation of clinical benefit by calculation of absolute risk reduction (ARR) und number needed to treat (NNT) will be described with a focus on psychiatric studies and examples. Meanwhile efforts are made by psychiatrists to make decisions on best evidence available at present in combination with clinical expertise.