Taking moderate to high daily doses of antidepressants for more than 2 years is associated with an 84% increased risk for diabetes, according to a large observational study conducted by a group from Bremen Institute for Prevention Research and Social Medicine in Bremen, Germany, based on the data from the U.K. General Practice Research Database. The increased risk was particularly notable for the selective serotonin-reuptake inhibitor (SSRI) paroxetine and the tricyclic antidepressant amitriptyline. Weight gain might explain much of the relation between antidepressant use and diabetes, according to the study authors.

Andersohn F, Schade R, Suissa S, Garbe E. Long-term use of antidepressants for depressive disorders and the risk of diabetes mellitus. Am J Psychiatry. 2009 May;166(5):591-8.

OBJECTIVE: Use of antidepressants has been reported to cause considerable weight gain. The aim of this study was to assess the risk of diabetes mellitus associated with antidepressant treatment and to examine whether the risk is influenced by treatment duration or daily dose.
METHOD: This was a nested case-control study in a cohort of 165,958 patients with depression who received at least one new prescription for an antidepressant between January 1, 1990, and June 30, 2005. Data were from the U.K. General Practice Research Database. Patients were at least 30 years of age and without diabetes at cohort entry.
RESULTS: A total of 2,243 cases of incident diabetes mellitus and 8,963 matched comparison subjects were identified. Compared with no use of antidepressants during the past 2 years, recent long-term use (>24 months) of antidepressants in moderate to high daily doses was associated with an increased risk of diabetes (incidence rate ratio=1.84, 95% CI=1.35-2.52). The magnitude of the risk was similar for long-term use of moderate to high daily doses of tricyclic antidepressants (incidence rate ratio=1.77, 95% CI=1.21-2.59) and selective serotonin reuptake inhibitors (incidence rate ratio=2.06, 95% CI=1.20-3.52). Treatment for shorter periods or with lower daily doses was not associated with an increased risk.
CONCLUSIONS: Long-term use of antidepressants in at least moderate daily doses was associated with an increased risk of diabetes. This association was observed for both tricyclic antidepressants and selective serotonin reuptake inhibitors.