There has been much recent debate and controversy over the apparent expansion of the use of certain psychiatric classifications, and the treatment of those so diagnosed, in particular their treatment with psychiatric drugs. Some have suggested that this arises from ‘disease mongering’ by a pharmaceutical industry keen to sell its products. Others have implied that psychiatrists are the key agents, acting as ‘moral entrepreneurs’ claiming that society is ignoring an area of suffering that they are best placed to understand and treat. Others have suggested that the expansion is part of a social and cultural malaise, in which individuals increasingly define problems of living as disorders in need of treatment. This article reviews the evidence of the expanding scope of psychiatric diagnosis, focusing on depression, attention deficit hyperactivity disorder and personality disorder. It examines a number of arguments that seek to account for this expansion and suggests that we need a more complex approach to understand the growth of these diagnoses, not only addressing marketing of drugs by pharmaceutical industry and the role of doctors, but also examining the pressures and incentives that lead to the ascription of such diagnoses and their treatment with drugs.