Those laboratory mice have been at it again. This time, we discover that when mice stop drinking moderate levels of alcohol they can become depressed around two weeks later. Mice are commonly used to model the effects of a number of conditions associated with human behavior. But how do we know when a mouse is depressed?
According to Clyde W.Hodge, Ph.D., professor of psychiatry and pharmacology at the UNC School of Medicine, the answer is found in the Porsolt Swim Test. Mice are very good swimmers, so placing them in water for six minutes presents no difficulty. The amount of time a mouse spends immobile is used as the measure for despair or depression. The longer a mouse floats, the more depressed it is considered to be.
According to Hodge, depression in mice is associated with a marked reduction in neural stem cells within the hippocampus region of the brain. Extending the model to humans, Hodge says:
" . . . people who drink moderate amounts of alcohol socially, or for potential health benefits, may experience negative mood or diminished cognitive abilities due to a loss of the brain's ability to form new neurons."
Interestingly, the application of antidepressant medication prevented depression developing further and had a restorative function on the brain allowing it to produce new cells.
Moderate intake of alcohol, particularly red wine, has been linked to health benefits. Molecules known as polyphenols are found in a variety of foods but the most potent polyphenol is resveratrol, found in red wine. Polyphenols have antioxidant properties and have most notably been linked to reductions in heart disease and certain cancers.
The fact that stopping moderate alcohol intake appears to have a negative effect on the hippocampus may be significant. The hippocampus is critical for learning and memory and recent studies are showing that it has a role in the regulation of moods.
"This research provides the first evidence that long-term abstinence from moderate alcohol drinking - rather than drinking per se - leads to a negative mood state, depression," Hodge said.