Drinking and depression have problematic relationship, so the consensus from recent studies that moderate red wine consumption correlates to lower odds of depression may seem hard to swallow. But it is clear that daily wine drinkers show a J-shaped curve for clinical depression: lower in moderation, higher in excess. Some very good data comes from a long term study called PREDIMED (“Prevención con Dieta Mediterránea” (Prevention with Mediterranean Diet)), which is a randomized, multicenter, controlled, clinical trial conducted in Spain involving more than 5500 subjects. At up to 7 years of follow-up, wine intake within the range of 2-7 drinks per week was significantly associated with lower risk of incident depression.
Resveratrol, wine’s miracle molecule, offers a potential explanation though it is likely the whole story. There is an experimental model of depression in rats, allowing for measurement of depressive symptoms in response to various drug treatments (no model yet for the effects of counseling or group therapy.) A recent study found that rats given resveratrol for one week exhibited a dose-dependent decrease in activities correlated to depression. More significantly, this effect was associated with an increase in hippocampal and frontal cortical brain-derived neurotrophic factor (BDNF), a protein implicated in chronic effects of many antidepressants.
While it is tempting to unite these findings into and conclude that wine drinkers have lower rates of depression because of the resveratrol, there is an obvious in that logic: Only moderate consumption of wine has a clinical correlation, and it is likely that much higher doses of resveratrol are needed to raise BDNF levels in the brain than what you get in a glass of wine. Both studies are true, but unrelated.
There are many other factors to consider, such as the role of alcohol, but it may be that moderate wine drinking is a marker for other lifestyle factors that relate to lower incidence of depression or elevation of BDNF in the brain. Maybe I will have a glass of wine and think about it.