We really don't know how anti-depressants or anti-anxiety work and are effective for some people. The Serotonin boost / balance is just one of the popular theor

We really don't know how anti-depressants or anti-anxiety work and are effective for some people. The Serotonin boost / balance is just one of the popular theories that is being studied as the cause for this. Let's not forget that for a really long time we believed the popular theory that stress caused ulcers. I also speculate that a major reason for the popularity of this Serotonin theory is largely covert and overt pharmaceutical marketing - doctors and patients are much more likely to "trust" a medicine if they believe there is a "scientific" explanation to why a medication works. (In case there is any doubt, I want to clarify that I that anti-depressants and anti-anxiety medications do work and relieve the symptoms of these disorders. Medical trials have been done to prove that they do work, are effective and also cause side-effects. But we really do not understand how they work with any scientific surety and hence also why they don't work for a minority of people.)