Why We Eat When We're Depressed, And Why We Get Depressed When We Eat

The perfect breakup cure may be a pint of ice cream and a movie marathon (or just tons of booze), but new research shows that binging might start the vicious cycle of eating and then feeling depressed and then eating some more.

Researchers at the University of Montreal have released a study on mice, showing the complicated relationship between food and emotion.

Past studies have shown that high-fat and high-sugar foods tend to cause a spike in dopamine, which triggers good feelings and acts as a rewards system. This dopamine spike led researchers to believe that fatty foods can be addictive, like drugs. University of Montreal researchers, however, have found that this reward system makes it difficult for people to get out of the cycle.

Led by Dr. Stephanie Fulton, the team divided mice into a high-fat/sugar diet group, and a normal control group.

After 12 weeks, the team discovered that the mice who ate more fats and sugars not only showed depression symptoms (giving up faster in a swimming test), but were also more anxious, were less likely to explore open areas, and had higher levels of corticosterone (a hormone associated with stress) than the control group.

Fulton mentioned that the obese mice's tendency to become more stressed could push them back toward eating comfort foods for the spike in dopamine. "Put animals and humans in a stressful situation, and when you give them the opportunity to eat high-fat foods, it relieves their stress," she said. "In the short term it can be very relieving, but in the long term for perpetuating that vicious cycle, it's an increase in inflammation and inducing behavior changes."

Behavior changes are also linked to a chemical change in the brain. Fulton suspects that the influx of dopamine and high-fat foods causes the brain to secrete more molecules associated with depressive behavior. Furthermore, by the end of the 12-week cycle, the researchers found that the fatty-diet mice often had very low levels of dopamine, meaning it was more difficult for them to reach the same sense of reward.

So what does it mean for the fight against obesity? "I think first and foremost we need to add mental disorders to the list of symptoms coupled with obesity," Fulton said. "We speak a lot about cancer and type 2 diabetes, but we need to recognize that it is a vicious cycle. For people who are already in that cycle, it's difficult to get out of it because it can be a lot harder to find other ways to seek rewards in different areas."

Fulton is also working on research examining how saturated fat specifically affects the emotional state of mice.