The clinical research is quite robust in showing that most people do not have antidepressant or anxiolytic responses to SSRI or buspirone in the first few days, whereas many of them have side effects that quickly. (Many studies suggest that under 5% of individuals will have a rapid positive response, and it is unclear how often this is a placebo response.) This is in marked contrast, for example, to ADHD symptoms responding within hours to stimulant medications.

This tells us that the immediate chemical effect of these medications is not what leads to relief from depression or anxiety. Numerous studies indicate that protein synthesis, receptor up- or down-regulation, and synaptogenesis need to occur for these drugs to work, and all of these responses are slowly developing reactions to the initial biochemical perturbation caused by the drugs.