Depression is most common in people with obesity, especially women. But the link between depression and obesity has been complex and unclear. Previous research has shown a higher body mass index (BMI) causes depression, but has not tested whether this relationship is driven by the metabolic consequences of BMI nor for differences between men and women. However, new research has found strong evidence that obesity causes depression.
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Scientists from the University of South Australia and the University of Exeter in the UK looked at medical and genetic information in the UK Biobank of 48,791 individuals with depression and 291,995 controls born between 1938 and 1971. Hospital data and self-reporting were used to determine whether people had depression. The researchers performed a Mendelian randomisation to test for causal effects of higher BMI on depression. The researchers used two genetic instruments, both representing a higher BMI, to separate the psychological component of obesity from the metabolic consequences of obesity such as diseases like diabetes. The researchers further tested a causal relationship in men and women using subsets of BMI variants.
The researchers found that a higher BMI was strongly associated with a higher chance of depression, especially in women. Genes associated with a higher BMI were just as strongly associated with depression, as those genes associated with higher BMI and diabetes suggest that being overweight causes depression with and without any other related health issues like diabetes. The study also found that on the other end of the BMI spectrum, very thin men are more prone to depression than men of normal weight or very thin women.
This evidence indicates that obesity causes depression and has a psychological impact on obese individuals, even in the absence of other health problems. Being overweight not only leads to increased risks of chronic diseases such as cardiovascular disease and cancer, but it also causes depression, a major concern both for people with obesity and also their healthcare providers.
Source: International Journal of Epidemiology
