chapter  4
Depression and anxiety Antidepressants
Pages 96

Effectiveness The severity of depression at which antidepressants show consistent benefits over placebo is poorly defined. In general, the more severe the symptoms, the greater the benefit 1,2 . Antidepressants are normally recommended as first-line treatment in patients whose depression is of at least moderate severity. Of this patient group, approximately 20% will recover with no treatment at all, 30% will respond to placebo and 50% will respond to antidepressant drug treatment 3 . This gives a NNT of 3 for antidepressant over true no-treatment control and an NNT of 5 for antidepressant over placebo. Note though that response in clinical trials is generally defined as a 50% reduction in depression rating scale scores, a somewhat arbitrary dichotomy, and that change measured using continuous scales tends to show a relatively small mean difference between active treatment and placebo.