The association between antidepressant treatment and rates of insulin initiation in comorbid depression and type 2 diabetes: A UK electronic health record nested case-control study

Aims To investigate the association between antidepressant prescribing and the rate of insulin initiation in type 2 diabetes. Methods Using UK primary care records we completed a nested-case control study in a individuals with comorbid depression and type 2 diabetes. Cases were defined as individuals initiating insulin, controls were individuals remaining on oral antidiabetic medication. We used conditional logistic regression to estimate incident rate ratios (IRR) and the 95% confidence intervals (CI) for the association between antidepressant prescribing and initiating insulin. We adjusted for demographic characteristics, comorbidities, health service and previous medication use. Results We included 11,862 cases who initiated insulin, and 43,452 controls. Increased rates of insulin initiation were associated with any antidepressant prescription (IRR 3.78, 95% CI 3.53–4.04), longer (24+ months) durations of antidepressant treatment (IRR 5.61, 95% CI 5.23–6.03), and higher numbers (3+) of different antidepressant agents prescribed (IRR 5.72, 95% CI 5.25–6.24). There was no difference between recent and non-recent antidepressant prescriptions, or between different antidepressant agents. Conclusions Antidepressant prescribing was highly associated with the initiation of insulin therapy. However, this may not indicate a direct causal effect of the antidepressant medication itself, and may be a marker of more severe depression influencing diabetic control.