Overweight and obese people may be at increased risk of depression, even in the absence of other health problems, warns new research.
The research, published in the International Journal of Epidemiology, showed that the psychological impact of being overweight causes depression, rather than associated illnesses such as diabetes.
"Our research shows that being overweight doesn't just increase the risks of chronic diseases such as cancer and cardiovascular disease; it can also lead to depression," said study co-author Elina Hypponen, Professor at the University of South Australia.
For the 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 were used to determine whether people had depression. The team used a genetic research approach to explore the causal link between the two conditions.
They separated out the psychological component of obesity from the impact of obesity-related health problems, using genes associated with higher BMI but lower risk of diseases like diabetes. "These genes were just as strongly associated with depression as those genes associated with higher BMI and diabetes. This suggests that being overweight causes depression both with and without related health issues - particularly in women," Hypponen said.
"Our robust genetic analysis concludes that the psychological impact of being obese is likely to cause depression. This is important to help target efforts to reduce depression, which makes it much harder for people to adopt healthy lifestyle habits," said Jess Tyrrell of the University of Exeter Medical School in Britain.