Manifestations of depression in people with intellectual disability.

The symptoms of 36 people with varying degrees of intellectual disability (ID) who had had an ICD-10 depressive syndrome in the preceding year were compared with 46 non-depressed people with comparable degrees of ID. Throughout the spectrum of ID, symptoms of depressed affect and sleep disturbance were significantly different between the groups. While symptoms in people with mild ID were reflected in the standard diagnostic criteria, this was not the case in people with moderate and severe ID. With increasing disability there was a move towards 'behavioural depressive equivalents' such as aggression, screaming and self-injurious behaviour. Diagnostic criteria for depression among people with severe ID, should place more emphasis on behavioural 'depressive equivalents'.