If you find yourself reaching for the cookie jar after a stressful day, the chances are your cravings are being fuelled by a hunger hormone known as ghrelin. Now, scientists are beginning to unravel the intimate relationship between hunger hormones, emotions, stress and energy levels in the hope of developing a treatment for stress-related anxiety and depression.
It's no secret that when some people feel depressed or under stress they seek out food. We've always thought of this as 'comfort eating' which provides solace in foods that are easy to eat and provide a sugar rush to make us feel better. Dr. Jeffrey Zigman and Dr. Michael Lutter of UT Southwestern, have identified that ghrelin levels increase when triggered by conditions of stress. As ghrelin levels increase so behaviors associated with anxiety and depression start to decrease. Of course the increase in ghrelin is associated with extra food intake and extra weight gain.
Dr. Zigman and colleagues restricted food intake in laboratory mice for 10 days. This introduced a condition of stress and ghrelin levels quadrupled. However, when subjected to stressful tasks such as mazes and other tests, these same mice displayed decreased levels of anxiety and depression when compared with mice who were normally fed.
In order to establish whether ghrelin could have a role in the treatment of stress-induced emotional problems, the researchers decided to genetically change some of the mice so they were unable to respond to ghrelin. Mice were then subjected to daily bouts of stress. Over time all the mice in the experiment were found to have elevated levels of ghrelin but those who had been genetically altered displayed more social avoidance and ate less, suggesting higher levels of depression-like symptoms.
An obvious contender for possible future treatments is anorexia nervosa. Many people with anorexia report less anxiety and greater emotional stability during periods of food restriction. Calorie restriction and weight loss may therefore have an anti-depressant effect and if this is the case it would reinforce the disease.
"However, this new research suggests that if you block ghrelin signaling, you might actually increase anxiety and depression, which would be bad," Dr.Zigman reported to ScienceDaily.
It is unclear which area of the brain ghrelin affects, so this is a likely target for future research.
UT Southwestern Medical Center (2008, June 16). Hunger Hormone Increases During Stress, May Have Antidepressant Effect. ScienceDaily. Retrieved June 16, 2008, from http://www.sciencedaily.com/releases/2008/06/080615142252.htm