Overweight and obese people may experience an increased risk of depression, even in the absence of other health problems, warn new research.
The study, published in the International Journal of Epidemiology, shows that the psychological impact of being overweight causes depression, rather than related diseases such as diabetes.
"Our research shows that being overweight not only increases the risk of chronic diseases such as cancer and cardiovascular disease, but can also cause depression," said study co-author Elina Hypponen, Professor at the University of South Australia.
For this study, the researchers looked at UK Biobank data from more than 48,000 people with depression, comparing them with a control group of more than 290,000 people born between 1938 and 1971, who provided medical and genetic information.
Hospital data and self-reporting are used to determine whether people are depressed.
The team used a genetic research approach to explore the causal relationship between the two conditions.
They separate the psychological component of obesity from the impact of obesity-related health problems, using genes associated with higher BMI but reducing the risk of diseases such as diabetes.
"These genes are as strong as depression like genes associated with higher BMI and diabetes. This shows that being overweight causes depression both with or without health problems related – especially in women," Hypponen said.
"Our strong genetic analysis concludes that the psychological impact of obesity tends to cause depression. This is important to help target efforts to reduce depression, which makes it much more difficult for people to adopt healthy lifestyle habits," said Jess Tyrrell of the University. Exeter Medical School in England.