The problem of under-diagnosis and under-treatment of depression has been identified as a major public health issue and measures have been taken to increase the recognition of depression and its treatment with antidepressants. The possibility of harm from the overuse of antidepressants has attracted far less attention. This review sets out evidence to show that inappropriate use of antidepressants (i.e. outside clinical indications, in excessive doses and for prolonged periods) constitutes a concerning public health problem. Antidepressant prescribing increased by between 4- and 10-fold in various age groups and countries in the last decade of the 20th century. The population of severely depressed patients (in whom antidepressants are accepted to be an effective treatment) who are not receiving antidepressants is probably much smaller than the population receiving these drugs inappropriately. We sound a note of caution for depression awareness campaigns. These apparently well-reasoned responses to the perceived under-recognition of depression can exacerbate over-prescribing. Unless prescribing patterns change, any benefits from increasing access to antidepressants for those with severe depression will be accompanied by significant harms due to inappropriate prescribing in conditions, such as mild depression, where antidepressants are not indicated.