The most commonly prescribed antidepressant (and antianxiety) medications out there are the SSRI, selective serotonin reuptake inhibitors. These include drugs like fluoxetine (Prozac), citalopram (Celexa), or sertraline (Zoloft). How these drugs work, however, is still up for debate. At first, everyone thought that, because these drugs increase levels of the neurotransmitter serotonin in the brain, that depression must be caused by low levels of serotonin, and the increase would make you feel better. We have since learned that this is not the case. Headaches don’t result from lack of aspirin, and depression doesn’t result from lack of serotonin. The next theory for how depression, and antidepressants, might work was the neurogenesis theory. We used to believe that you were born with all the neurons you’d ever have, but we now know that neurogenesis, the birth of new neurons, occurs throughout life in areas of the brain like the hippocampus, an area usually associated with learning and memory. Antidepressants can increase neurogenesis, on a time course which matches the clinical efficacy of antidepressants. But now we are starting to think that it might be more complicated than that (via Stress and antidepressants: by their powers combined | The Scicurious Brain, Scientific American Blog Network)
