PCSK9 and major depressive disorder: The study results showed an increase in the PCSK9 levels in the obese subjects, associated with the Beck Depression Inventory (BDI). As depression is associated with an increased risk of diabetes, the identification of PCSK9 levels in depressed obese patients may identify people who are at increased risk of cardiovascular morbidity and could benefit the most from targeted intervention [43]. Table 1 demonstrates five important studies that focus on the associations between CVD and depression.