Replication and contradiction of highly cited research papers in psychiatry: 10-year follow-up

Background Contradictions and initial overestimates are not unusual among highly cited studies. However, this issue has not been researched in psychiatry. Aims To assess how highly cited studies in psychiatry are replicated by subsequent studies. Method We selected highly cited studies claiming effective psychiatric treatments in the years 2000 through 2002. For each of these studies we searched for subsequent studies with a better-controlled design, or with a similar design but a larger sample. Results Among 83 articles recommending effective interventions, 40 had not been subject to any attempt at replication, 16 were contradicted; 11 were found to have substantially smaller effects and only 16 were replicated. The standardised mean differences of the initial studies were overestimated by 132%. Studies with a total sample size of 100 or more tended to produce replicable results. Conclusions Caution is needed when a study with a small sample size reports a large effect.