Patients taking certain antipsychotics appear to be at increased risk of developing type 2 diabetes, BMJ Open reports.

Researchers analysed data collected from 262,982 people (aged between 40 and 60 years in 2006) who received metformin at any time until 2011. Of these, 24,493 received at least one antipsychotic.

The authors used metformin as a “proxy” for “clinically significant” type 2 diabetes that could not be modified by lifestyle changes. The authors could not allow for metformin’s other less common indications, such as polycystic ovary syndrome.

Patients dispensed a second-generation antipsychotic were 49 per cent more likely to start metformin compared with untreated controls.

Patients prescribed clozapine or olanzapine, which have a high risk of inducing weight gain, were 2.41 times more likely to start metformin. The analysis could not, however, allow for adherence.