Weight gain has long been recognised as one of the side effects of antipsychotic drugs. Weight gain can lead to other illnesses or health problems, such as glucose intolerance, diabetes, metabolic syndrome, sleep apnoea and cardiovascular diseases. At the same time fear of weight gain can lead to patients not taking their drugs which may lead to a failure to recover. It can be hard to pinpoint the effects of the drugs particularly if patients have been taking them for some time or if they are on other medication. A team of researchers from Bologna University in Italy reviewed 11 studies into people who were taking antipsychotic drugs for the first time. They found that, on average, the patients put on 3.8kg. Weight gain occured rapidly in the first few weeks and continued during the following months.
Tarricone, I. ... [et al] - Weight gain in antipsychotic-naive patients: a review and meta-analysis Psychological Medicine February 2010, 40(2), 187-200