Marital rows can make people put on weight by slowing down the metabolism, a study suggests.
Unhappy couples in marriages fraught with tension were found to be at a higher risk of obesity because their arguments caused them to burn fewer calories.
Those with a history of depression as well as a hostile marriage were found to be particularly prone to metabolic problems as their rows altered the way the body processed high-fat foods.
The lead researcher, Jan Kiecolt-Glaser, from Ohio State University, said: "Meals provide prime opportunities for ongoing disagreements in a troubled marriage, so there could be a long-standing pattern of metabolic damage stemming from hostility and depression." Researchers gave 43 healthy couples aged 24 to 61, who had been married for at least three years, a meal totalling 930 calories and 60g of fat.
The couples were asked to try to resolve issues that often caused conflict. Common topics were money, communication and in-laws.
They were then monitored for seven hours. Those with a mood disorder and a more hostile marriage burned an average of 31 fewer calories an hour.
Kiecolt-Glaser, the university's director of Institute for Behavioural Medicine Research, said: "These findings not only identify how chronic stressors can lead to obesity, but also point to how important it is to treat mood disorders.
"Interventions for mental health clearly could benefit physical health as well."