Comments on the discussion of major depression as an adaptation by R.M. Nesse. The present author argues that one cardinal symptom of depression that Nesse fails to discuss is suicidal behaviour. The author argues that there is no way that suicidal thoughts or behaviours can lead to a person’s surviving any situation. Even if suicidal behaviour in an individual somehow conveyed an advantage to the species as a whole, genetically determined suicidal behaviour would rapidly be selected against as individuals who display it kill themselves before being able to increase the frequency of these ‘suicidal’ genes in the population by reproducing. Suicide (and hence severe depression) can thus only be seen as a disease state that conveys no benefits to an individual. (2 refs)