A study published in the Lancet in February 2018 found that antidepressants are more effective in patients with moderate-severe depression or major depressive disorder than placebo (see Cipriani et al. (2018)). This study reviewed results from >500 trials, that evaluated 21 different drugs, and involved >100,000 patients with depression- but note the caveat that the team could only work with the results as originally published, and experience indicates that trial results may sometimes have been analysed so as to present the most positive of outcomes. So, at least for patients with severe depression, the use of antidepressants appears to be justified. However, the majority of patients present with mild-to-moderate depression, and it is still unclear if antidepressant therapy is effective in these patients. Criticisms of the use of antidepressants in patients with milder forms of the disease are multi-fold: Are they effective in this patient group? Are they prescribed to easily and too often for mild depression? Are patients warned about the range/severity of side-effects? Are they adequately warned of the issues surrounding withdrawal? Add to this mix of concerns the subjectivity and diversity of patients' experiences and responses to the benefits and side-effects of therapy, and the efficacy of antidepressant therapy in the mildly depressed patient is obscured even further.
For information regarding the pharmacology of the antidepressant drug classes used in clinical practice see our Antidepressant drugs topic.