It is normal to feel depressed. In our cohort study of 242 teachers, the 1978 baseline questionnaire defined depression as “a significant lowering of mood, with or without feelings of guilt, hopelessness and helplessness, or a drop in one's self-esteem or self-regard.”1 Ninety five per cent of the cohort reported such feelings (with a mean of six episodes a year), indicating the ubiquitous nature of depressed mood states.

A low threshold for diagnosing clinical depression, however, risks normal human emotional states being treated as illness, challenging the model's credibility and risking inappropriate management. When the first antidepressant (imipramine) was developed, manufacturer Geigy was reluctant to market it,2 judging there were insufficient people with depression. Now, depression is all around, and antidepressant drugs have a dominant share of the drug market. Reasons for the overdiagnosis include lack of a reliable and valid diagnostic model and marketing of treatments beyond their true utility in a climate …