Comfort eating among people who are stressed or depressed may be explained by the action of a “hunger hormone”, according to research.

Experiments with mice have suggested that the body makes extra amounts of an important appetite hormone to combat the effects of stress-induced depression and anxiety, which in turn prompts overeating.

The findings, by a team from the US, could have implications for understanding eating disorders such as anorexia nervosa and bulimia nervosa.

When both mice and people do not eat, levels of a hormone called ghrelin rise in the gut, sending increased hunger signals to the brain.

The study, led by Jeffrey Zigman, of the University of Texas Southwestern Medical Centre , in Dallas, has indicated that the body also produced extra quantities of ghrelin in response to stress. This hormone synthesis seems to be part of the body's natural defence against stress, as it tends to reduce typical depressive and anxious behaviour. However, it also boosts appetite, leading to comfort eating.

“Our findings in mice suggest that chronic stress causes ghrelin levels to go up and that behaviours associated with depression and anxiety decrease when ghrelin levels rise,” Dr Zigman said. “An unfortunate side-effect is increased food intake and body weight.”

Michael Lutter, another member of the research team, said: “Our findings support the idea that these hunger hormones don't do just one thing. Rather, they co-ordinate an entire behavioural response to stress and probably affect mood, stress and energy levels.”

The research, published in the journal Nature Neuroscience, raises the prospect that blocking the body's response to ghrelin might help people who comfort-eat to control their weight. However, it also suggests that this approach might be problematic, as it could also reduce ghrelin's beneficial effects on mood and stress response, so that susceptible people suffer in different ways.

Dr Zigman said: “This new research suggests that, if you block ghrelin signalling, you might actually increase anxiety and depression, which would be bad.”

Dr Lutter said that, despite this drawback, the research could shed important light on the biological processes behind some eating disorders. “We're very interested to see whether ghrelin treatment could help people with anorexia nervosa: the idea being that, in a certain population, calorie restriction and weight loss could have an antidepressant effect and could be reinforcing for this illness,” he said.

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