Confirmation bias: why psychiatrists stick to wrong preliminary diagnoses.

BACKGROUND: Diagnostic errors can have tremendous consequences because they can result in a fatal chain of wrong decisions. Experts assume that physicians' desire to confirm a preliminary diagnosis while failing to seek contradictory evidence is an important reason for wrong diagnoses. This tendency is called 'confirmation bias'. METHOD: To study whether psychiatrists and medical students are prone to confirmation bias and whether confirmation bias leads to poor diagnostic accuracy in psychiatry, we presented an experimental decision task to 75 psychiatrists and 75 medical students. RESULTS: A total of 13% of psychiatrists and 25% of students showed confirmation bias when searching for new information after having made a preliminary diagnosis. Participants conducting a confirmatory information search were significantly less likely to make the correct diagnosis compared to participants searching in a disconfirmatory or balanced way [multiple logistic regression: odds ratio (OR) 7.3, 95% confidence interval (CI) 2.53-21.22, p<0.001; OR 3.2, 95% CI 1.23-8.56, p=0.02]. Psychiatrists conducting a confirmatory search made a wrong diagnosis in 70% of the cases compared to 27% or 47% for a disconfirmatory or balanced information search (students: 63, 26 and 27%). Participants choosing the wrong diagnosis also prescribed different treatment options compared with participants choosing the correct diagnosis. CONCLUSIONS: Confirmatory information search harbors the risk of wrong diagnostic decisions. Psychiatrists should be aware of confirmation bias and instructed in techniques to reduce bias.

The cyclooxygenase-2 inhibitor celecoxib has therapeutic effects in major depression: results of a double-blind, randomized, placebo controlled, add-on pilot study to reboxetine.

Signs of an inflammatory process, in particular increased pro-inflammatory cytokines and increased levels of prostaglandine E(2) (PGE(2)), have repeatedly been described in major depression (MD). As cyclooxygenase-2 (COX-2) inhibitors inhibit the PGE(2) production and the production of pro-inflammatory cytokines, we performed a therapeutic trial with the COX-2 inhibitor celecoxib. In a prospective, double-blind, add-on study, 40 patients suffering from an acute depressive episode were randomly assigned to either reboxetine and celecoxib or to reboxetine plus placebo. After a wash-out period, 20 patients received 4-10 mg reboxetine plus placebo and 20 received reboxetine plus 400 mg celecoxib for 6 weeks. The treatment effect was calculated by analysis of variance. There were no significant differences between groups in age, sex, duration or severity of disease or psychopathology, or reboxetine dose or plasma levels. Over 6 weeks, both groups of patients showed significant improvement in scores of the Hamilton Depression Scale. However, the celecoxib group showed significantly greater improvement compared to the reboxetine-alone group. Additional treatment with celecoxib has significant positive effects on the therapeutic action of reboxetine with regard to depressive symptomatology. Moreover, the fact that treatment with an anti-inflammatory drug showed beneficial effects on MD indicates that inflammation is related to the pathomechanism of the disorder, although the exact mechanisms remain to become elucidated.