The idea that depression is caused by a chemical imbalance—specifically, a serotonin deficiency—has been popular and influential since the 1960s, leading to the wide use of antidepressants. A recent multi-institution study led by the University of Reading, in the UK, and published in Molecular Psychiatry has debunked this theory. The researchers did a systematic review of studies on the topic and found no convincing evidence of an association between serotonin and depression, and no support for the hypothesis that depression is caused by lowered serotonin activity or concentrations. The serotonin theory of depression has historically provided convincing justification for the use of antidepressants and may discourage people from discontinuing treatment, potentially leading to lifelong dependence on such drugs.