While antidepressant prescription rules are established for approved indications by large-scale studies, off-label utilization naturally often lacks the validation by large scientific databases, and is at its best based on expert consensus. The aim of the present survey was to study the prescription habits of hospital psychiatrists with regard to antidepressants, comparing patients treated for depressions and anxiety disorder with patients receiving off-label antidepressant treatment. METHODS: Data on drug use for this study were based on 6 reference days from April 1999 to November 2001 in the 98-bed psychiatric hospital of the University of Lausanne, Switzerland. The drug prescriptions of 174 patients were assessed. RESULTS: Whereas the diagnosis did not influence the choice between newer or older antidepressants, patients presenting an anxiety disorder were 4.5 times more likely (p<0.05) and patients with other diagnoses 8 times more likely (p<0.001) to receive an antipsychotic comedication compared to patients whose primary diagnosis was a depressive disorder. Also, patients receiving concomitantly a nonbenzodiazepine hypnotic were less likely to be prescribed an older antidepressant (p<0.05). While patients with anxiety disorder and those with major depression received their antidepressants at comparable doses, patients with an off-label indication were treated preferentially with lower doses. CONCLUSIONS: The results of this survey suggest, that the prescribing hospital psychiatrists developed preferences with regard to the choice of the antidepressant class, which they then used for both registered and off-label indications. They then seemed to adapt the dose and the comedication according to the diagnosis, confirming the initial study hypothesis.