Severity of unipolar depression and choice of treatment.

The National Institute of Mental Health (NIMH) Treatment of Depression Collaborative Research Program (Elkin et al., Archives of General Psychiatry, 46, 971-982; 1989) reported treatment-by-severity interactions favouring pharmacotherapy for more depressed outpatients, on a minority of relevant comparisons. The present study reports secondary analyses from a similar, preexisting data set in which treatment-by-severity interactions are systematically investigated with depressed outpatients treated either with nondirective psychotherapy, behaviour therapy, pharmacotherapy, or relaxation/placebo. Despite multiple severity measures and variable severity cut scores, no treatment was differentially effective in improving more severely depressed patients. Also, there was little difference across symptom severity levels in the proportions of recovered patients between treatment groups. Finally, dynamic cluster analysis demonstrated that the proportion of pharmacotherapy nonresponders (20%) did not differ from the proportion of nonresponders in behaviour therapy or placebo groups. It is concluded that this failure to replicate the NIMH trial findings can not be attributed to treatment differences, populations or statistical power. The suggestion that pharmacotherapy be the treatment of choice for more severely depressed outpatients appears to be unjustified on the basis of available evidence.