Genetic and environmental factors contribute to the overlap between depression and metabolic endocrine diseases

picture:

Co-existence in families

In the study researchers identified 2.2 million individuals born in Sweden between 1973 and 1996, as well as their full and half siblings, and followed them until the age of 40. A number of medical conditions have been studied. Depression and various endocrine and metabolic diseases, including three autoimmune diseases (autoimmune hypothyroidism, Graves’ disease and type 1 diabetes) and three non-immune diseases (type 2 diabetes, obesity and PCOS).

People with endocrine and metabolic diseases have a 1.4 to 3.5 times increased risk of depression compared to those without these diagnoses. Their full siblings and half-siblings also had some risk of developing depression, suggesting that genetic and/or environmental risk factors shared by family members play a role in the occurrence of these mental and physical disorders.

genetic and environmental influence

By comparing full sibling pairs (who share about half of their genes) with pairs of non-siblings (who share about a quarter of their genes), it was possible to calculate the relative contribution of genetic and environmental factors to the co-occurrence of depression and various endocrine and metabolic diseases.

Results varied between autoimmune diseases and autoimmune diseases. The overlap between depression and non-autoimmune conditions was mainly explained by shared genetic influences, while environmental factors were mainly implicated in the association between depression and autoimmune diseases, especially type 1 diabetes.

This suggests that the association between depression and various endocrine and metabolic disorders may be driven by different mechanisms. For example, shared biological mechanisms, such as immune inflammation and metabolic disturbance, may underlie the co-existence of depression, type 2 diabetes, obesity, and polycystic ovary syndrome. However, the absence of co-genetics in the association between type 1 diabetes and depression may reflect the presence of environmental factors influencing risk for both conditions and/or a direct link between these conditions through mediating factors – eg. The biological and psychosocial mechanisms associated with type 1 diabetes, including inflammation and brain damage, as well as the stress of this lifelong condition often diagnosed early in life, require a complex treatment regimen for both patients and their families.

Our results confirm that clinicians should be aware of the increased risk of depression in individuals with endocrine and metabolic diseases, and vice versa, and be alert to common symptoms. Our study also provides a useful basis for future research aimed at identifying and targeting the biological mechanisms and modifiable risk factors underlying the co-morbidity of endocrine and metabolic diseases and depression, says Marica Lyon, first author of the study.

The study was funded by the European Union’s Horizon 2020 Research and Innovation Program under Marie Sklodowska-Curie Grant Agreement No. 721567.

Publishing

Genetic and environmental contribution to the incidence of endocrine and metabolic disorders and depression: a Swedish nationwide sibling study.
Leon M, Koja-Halkola R, Leval A, Potoica A, Skov C, Zhang R, Leos, Larson H, Bergen C
I J Psychiatry 2022 Sep; (): appiajp21090954