When we are depressed our brains undergo many different biochemical changes; no one is quite certain which of these actually cause the typical feelings of sadness or hopelessness.
One important depression-related change is a dramatic decline in the birth of immature neurons, known as neurogenesis, in a brain region called the hippocampus.
Drugs that treat depression, such as Prozac and Zoloft, all induce a recovery in the rate of neurogenesis in the hippocampus.
So what’s the connection with marijuana and the munchies?
The drug, rimonabant, that was so successful in reducing food cravings as it induced depression and thoughts of suicide, has been recently shown (by Beyer and colleagues at Pfizer) to significantly reduce neurogenesis.
Let’s flip this idea on its side and ask, “What would happen to neurogenesis if we exposed the brain to marijuana?”
My lab investigated this idea and discovered that a small dose of marijuana, about only one puff, taken every day can reverse the age-related decline in neurogenesis that might underlie depression.
Whether this approach might also work in young people remains to be determined.
What these studies teach us is that our brain’s own marijuana neurotransmitter system is necessary for us to feel hungry, to experience happiness and to maintain the brain normal processes, such as neurogenesis, that prevent age-associated depression and cognitive decline.
We’ve learned from our experience with rimonabant that it is dangerous to constantly antagonize this neurotransmitter system.
What we do not know is whether it is dangerous to constantly stimulate it.