This is actually quite interesting. I'd love to see some hard data on the actual impact this use had on the serotonergic system; for as large a part as it plays in the brain, and all of the diseases that we believe are related to it (everything from mental illnesses like depression and schizophrenia to migraines and cluster headaches), we really know very little about it. Our current drugs acting on serotonin receptors are brute-force hacks -- we need to know a whole, whole lot more.