Weight gain associated with neuroleptics or antipsychotic treatment is well 
known by psychiatrists, but is too rarely considered as justifying a specific 
treatment program. Overweight is a risk factor for somatic disorders and can 
have a negative influence on self-esteem and self-confidence. This can lead to 
poor observance, and relapse of psychotic symptoms. Some studies try to describe 
the weight fluctuations according to the different neuroleptics and taking into 
account other variables like treatment duration, age or sex. Mechanisms of 
weight gain are less studied, in spite of evidence that neuroleptics interact 
with receptors of dopamine, norepinephrine, serotonin, histamine and 
acetylcholin, all implicated in a way or another, in weight regulation. 
Antipsychotics, like clozapine and olanzapine, are more concerned with 
neuroendocrine and neurovegetative interactions, and are responsible for the 
most severe weight increases. Loxapine and molindone induce weight decreases, 
and these exceptions are difficult to explain. The paper discusses the clinical 
and the epidemiological data, and indicates the methodological problems for such 
studies. Some hypotheses about the pathophysiological aspects of this side 
effect are made, in regard to growing knowledge about the biological mechanisms 
of weight regulation. Some solutions for a better consideration and caretaking 
of patients with such problems or "at risk" treatment are proposed.