Insula thickness asymmetry relates to risk of major depressive disorder in middle-aged to older adults.

A growing body of research implicates the insula as a critical brain structure in major depressive disorder (MDD), emotional salience, and interoception. Despite a high prevalence of depressive symptoms among middle-aged to older adults and the elevated risks that they confer towards poor outcomes like deteriorating health and suicidality, only limited research has examined the role of the insula in this population. The present study investigates associations between insula thickness and risk of developing MDD in middle-aged to older adults. A composite measure of MDD risk was quantified based upon current Beck Depression Inventory-II scores, current antidepressant medication use, and self-reported history of depression. Linear regressions were performed to analyze the relationships between insula thickness and MDD risk. Linear regression established that left-right insula thickness difference and left insula thickness significantly predicted MDD risk; however, right insula thickness did not. These findings provide evidence of the importance of insula thickness in middle-aged to older adults at elevated risk for MDD, while highlighting the left insula as an area of particular interest.