Mortality and Suicide Related to Major Depressive Disorder Before and After Type 2 Diabetes Mellitus

This study investigated differences in suicide and all-cause mortality from ICD-9-CM comorbid major depressive disorder (MDD) and type 2 diabetes mellitus (T2DM) depending on which was diagnosed first.

A longitudinal administrative claims database including 2 million samples and national death registry data from 2000 through 2015 in Taiwan were used. Patients with newly diagnosed T2DM were identified and further classified into 3 groups: (1) MDD before T2DM, (2) T2DM without any diagnosis of MDD (from which matched controls were selected), and (3) MDD after T2DM, based on the sequential occurrence dates between incident T2DM and MDD. Multivariable Cox proportional hazard models were analyzed.

Both the MDD before T2DM and MDD after T2DM groups had significantly higher risks of all-cause mortality (adjusted hazard ratio [AHR] = 1.21; 95% CI, 1.08-1.35 and AHR = 1.55; 95% CI, 1.45-1.66, respectively) and committed suicide (AHR = 5.05; 95% CI, 2.46-10.37and AHR = 14.32; 95% CI, 7.44-27.55, respectively) than their matched controls, while the MDD before T2DM and MDD after T2DM groups exhibited differences in mortality (significant; P < .0001) and death by suicide (nonsignificant).

The study findings indicated suicide and mortality rates were higher in both the MDD before and MDD after T2DM groups when compared with matched controls. Public health initiatives are needed to survey and treat comorbid MDD with T2DM. Furthermore, additional studies are needed to clarify the underlying pathophysiology of the association between MDD and T2DM to find better suicide prevention strategies among those high-risk patients who have comorbid T2DM and MDD.