Nature and Technology in Harmony!

Antipsychotics are a class of medications that revolutionised the practice of psychiatry when they first came out in the 1950’s. However some antipsychotics can cause weight gain in some people. A new review paper published in the British Journal of Psychiatry by Dr Alvarez-Jimenez and colleagues looks at ways to combat this weight gain using non-medication solutions. The authors used various medical databases to find research looking at this issue. They only included randomised controlled trials – that is studies where people are randomised into treatment or an alternative approach. 10 studies were found which satisfied their entry criteria. From the pooled studies, a total of 482 people using antipsychotic medication were given interventions which included cognitive-behavioural therapy (CBT), dietary counselling and exercise.  Compared to treatment as usual these approaches reduced weight by an average of 2.56kg.

When they looked at the different approaches they did find that the average effect differs for instance between dietary counselling and CBT. However when they looked at the confidence interval they found that there was an overlap and it wasn’t possible to conclude that there was a difference. So what’s the confidence interval? Well the idea is that the subjects in the study are representatives of a larger population. They’re samples from this population. Therefore any conclusions drawn are going to be estimates about the larger population. In this case, rather than drawing conclusions with certainty, the language of probability is used. For instance if we look at the average weight loss of 2.57kg above, in the study they actually include a 95% confidence interval of 1.92-3.2kg. That means that if you took 100 groups of 482 patients you would expect to see a weight loss of between 1.92 and 3.2kg in 95% of cases. That’s a very useful prediction.

However there were a few cautions that the authors advised. The follow-up period was short. So it was possible that if in the longer term exercise and dietary habits changed and weight gain returned, this wouldn’t have been picked up. Another difficulty was the pattern of the data. When performing a meta-analysis – an overview of lots of papers – the assumption is that the data falls in a normal distribution. Essentially that means that in a population there will be a few people who score very highly, a few people that score very low and the majority of people scoring in the middle range. Some of the studies reviewed here had a skewed pattern instead of the symmetrical pattern and statistical methods remain to be developed for such patterns. The researchers used the statistical methods for the more symmetrical distributions. The authors recommended that further studies were carried out looking at weight loss in the longer term.

The study shows that when medication is combined with exercise (and other methods) the weight gain side effects of medication can be countered.


Alvarez-Jimenez et al. Non-pharmacological management of antipsychotic-induced weight gain: systematic review and meta-analysis of randomised controlled trials. The British Journal of Psychiatry. 2008. 193. pp101-107.


The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor.


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