The efficacy of SSRIs and the serotonin hypothesis for depression are being questioned.

“you know the original mono amine hypothesis came from studies where they would just give people you know excess amounts of serotonergic drugs or take serotonin away from people the serotonin depletion studies and so it's quite a complex thing or a tryptophan depletion studies and so there's this you know there's this amino acid tryptophan which we get in our diets which is made into melatonin and serotonin and so it's a lot of sort of it's a lot of extrapolation to say that oh if you deprived someone at tryptophan and they don't make enough serotonin they're not going to feel good”