The study of 3,147 adults with impaired glucose tolerance showed that antidepressants, including SSRIs and tricyclics, increased the risk of developing diabetes two- to three-fold.
The findings, from the Diabetes Prevention Program, were presented at the American Diabetes Association's annual scientific sessions in Washington DC this month.
Although some antipsychotic drugs are known to increase a person's risk of developing diabetes, this is the first suggestion that antidepressants could have the same effect.
At the beginning of the study, 5.7 per cent of participants were on antidepressants and 10.3 per cent had likely depression.
After three years of follow-up, patients treated with a lifestyle-intervention programme were three times more likely to have type-2 diabetes if they used antidepressants. Those on placebo rather than the lifestyle intervention programme were twice as likely to develop the condition if they used antidepressants.
But patients with depression who were not taking antidepressants had no elevated risk.
David Taylor, chief pharmacist at the Maudsley Hospital in London, said: 'It could be a statistical anomaly or it could be an alert to some reaction between the drugs and diabetes that we were not aware of.'
Dr Rodger Gadsby, a Warwickshire GP with an interest in diabetes, said that it was too soon for GPs to change their practice: 'These are preliminary findings with no clear mechanism for them identified.'
But Dr Tim Saunders, Chester GP and PCT diabetes lead, said: 'GPs should bear it in mind when making treatment decisions.'
American Diabetes Association 66th Annual Scientific Sessions
Live links at GPonline.com.