Posttraumatic stress disorder and incidence of type-2 diabetes: A prospective twin study

• We examine whether PTSD is associated with incidence of type-2 diabetes.
• We use a longitudinal twin study design.
• PTSD is prospectively associated with a 40% increased risk of type-2 diabetes.
• Twins discordant for PTSD do not differ in their risk of diabetes.
• Common mechanisms may lead to both PTSD and insulin resistance/diabetes.

Growing evidence has linked posttraumatic stress disorder (PTSD) to insulin resistance and type-2 diabetes, but most previous studies were cross-sectional. We examined the association between PTSD and incidence of diabetes in a prospective study of middle-aged male twins from the Vietnam Era Twin Registry. Lifetime PTSD was diagnosed at baseline with the Diagnostic Interview Schedule (DIS) according to DSM-III-R criteria. Subthreshold PTSD was defined by meeting some, but not all, criteria for PTSD. A total of 4340 respondents without self-reported diabetes at baseline were included. Of these, 658 reported a new diagnosis of treated diabetes over a median of 19.4 years of follow-up. At baseline, twins with PTSD showed more behavioral and metabolic risk factors such as overweight and hypertension. The age-adjusted cumulative incidence of diabetes was significantly higher in twins with PTSD (18.9%) than those without PTSD (14.4%), [odds ratio (OR) = 1.4, 95% confidence interval (CI) 1.03–1.8], and intermediate in those with subthreshold PTSD (16.4%) (OR = 1.2, 95% CI 0.9–1.5, p for trend = 0.03). Adjustment for military, lifestyle and metabolic factors diminished the association. No significant association was found comparing twin pairs discordant for PTSD. In conclusion, PTSD was prospectively associated with a 40% increased risk of new-onset type-2 diabetes which was partially explained by a cluster of metabolic and behavioral risk factors known to influence insulin resistance. Shared biological or behavioral precursors which occur within families may lead to both PTSD and insulin resistance/diabetes. Thus, PTSD could be a marker of neuroendocrine and metabolic dysregulation which may lead to type-2 diabetes.