Diabetes is one of the most prevalent non-communicable disease conditions worldwide, with prevalence numbers continuously outnumbering prior predictions. According to the latest atlas from the International Diabetes Federation, there are currently 537 million adults living with diabetes, a number that is expected to increase to a staggering 783 million within the next 20 years (Sun et al., 2022). The vast majority of these people have type 2 diabetes, the form of diabetes characterized by a combination of insulin resistance and (relative) insulin deficiency and with clear links to obesity and sedentary life-styles. The process leading to type 2 diabetes probably starts many years before actual disease onset, explaining the high number of people living with a form of prediabetes, and continues to progress after diagnosis with continuing decline in beta-cell function. This explains why already more than one in five persons living with type 2 diabetes require (intensive) insulin treatment (Garg et al., 2018).

Since insulin and glucose can cross the blood-brain barrier, there is increasing attention for possible associations between diabetes and neuropsychiatric or neurodegenerative conditions, as exemplified by the PRIME project (https://prime-study.eu/). The recent reporting of genetic overlap between type 2 diabetes (and obesity) with several of these neuropsychiatric disorders, including Alzheimer’s Disease (AD), autism, attention-deficit hyperactivity disorder (ADHD) and major depressive disorder (MDD), provide further insight in common pathophysiological pathways linking these conditions (Fanelli et al., 2022).

Links between diabetes and mood disorders that are typically bi-directional (Nouwen et al., 2010, Mersha et al., 2022, Yu et al., 2015), have long been thought to be clinically explained, e.g. by the high burden of disease and adverse lifestyle habits, respectively. Although these factors definitely play a role, the genetic overlap between type 2 diabetes and MDD provides evidence for a biological basis. Interestingly, a review of Mendelian randomization studies now suggests this genetic component to contribute more to the higher risk of type 2 diabetes associated with MDD, but not (or less) so for the reverse relationship (Possidente et al., 2023).




Sources - https://www.sciencedirect.com/science/article/pii/S0149763424002446