Checkout the NYT Magazine article “Post-Prozac Nation: The Science and History of Treating Depression” by Siddhartha Mukherjee. Here is an excerpt:

We “grow sorrowful,” but we rarely describe ourselves as “growing joyful.” Imprinted in our language is an instinct that suggests that happiness is a state, while grief is a process. In a scientific sense too, the chemical hypothesis of depression has moved from static to dynamic — from “state” to “process.” An antidepressant like Paxil or Prozac, these new studies suggest, is most likely not acting as a passive signal-strengthener. It does not, as previously suspected, simply increase serotonin or send more current down a brain’s mood-maintaining wire. Rather, it appears to change the wiring itself. Neurochemicals like serotonin still remain central to this new theory of depression, but they function differently: as dynamic factors that make nerves grow, perhaps forming new circuits. The painter Cézanne, confronting one of Monet’s landscapes, supposedly exclaimed: “Monet is just an eye, but, God, what an eye.” The brain, by the same logic, is still a chemical soup — but, God, what a soup.

(Find the illustration above in The Daily Beast post “Depression Is Linked to Hyperconnectivity of Brain Regions, a New Study Shows.”)