If we read the multiple editions of the DSM and especially the last one, we have to admit that mental disease is always recognized through behavioural criteria. It should seem obvious that a good method to individuate mental diseases must be founded on behavioural observations. Deviation from habitual behaviour could be the manifestation of mental illness. Not always, obviously, as it is adequately remarked on the DSM definition of mental illness. However, can we really assume that the usual behaviour should be automatically definable as normal? Many people probably will answer affirmatively to this question. But if we propose the opposite question – that is, if we can define an unusual behaviour as abnormal – then the answer becomes less indisputable: not only because different cultures have different concepts of unusual behaviour and different degrees of tolerance of it, but especially because these concepts and degrees have changed through the ages.

To examine this problem in depth, we will focus our attention on a specific historical environment, the Mediterranean one, which offers us the opportunity of analysing, both contemporarily and in mutual relationships, many different approaches to the evolution of the concept of abnormal behaviour and, consequently, different evaluations of mental illness. This environment is particularly convenient for our purposes because of the variety of cultures that have grown and that currently exist in the Mediterranean area. This historical approach could be useful to avoid a drastic and narrow concept of normality, helping us to put ourselves in a more flexible attitude towards unusual behaviour and consequently towards mental illness.