The U.S. investigators looked at those taking selective serotonin reuptake inhibitors (SSRI), the most commonly prescribed type of anti-depressant. 

SSRIs are usually the first choice medication for depression and other psychiatric conditions because they generally have fewer side effects than most other types of antidepressant. 

Writing in the report, published in the Journal of Clinical Psychiatry, the researchers concluded: ‘Many individuals prescribed antidepressants may not have met the criteria for mental disorders.