Siddhartha Mukherjee provides a brief history of the serotonin hypothesis of depression, its demise and why dismissing serotonin may be an “overcorrection.”
Part of this story is an emerging theory of depression:
A remarkable and novel theory for depression emerges from these studies. Perhaps some forms of depression occur when a stimulus — genetics, environment or stress — causes the death of nerve cells in the hippocampus. In the nondepressed brain, circuits of nerve cells in the hippocampus may send signals to the subcallosal cingulate to regulate mood. The cingulate then integrates these signals and relays them to the more conscious parts of the brain, thereby allowing us to register our own moods or act on them. In the depressed brain, nerve death in the hippocampus disrupts these signals — with some turned off and others turned on — and they are ultimately registered consciously as grief and anxiety. “Depression is emotional pain without context,” Mayberg said. In a nondepressed brain, she said, “you need the hippocampus to help put a situation with an emotional component into context” — to tell our conscious brain, for instance, that the loss of love should be experienced as sorrow or the loss of a job as anxiety. But when the hippocampus malfunctions, perhaps emotional pain can be generated and amplified out of context — like Wurtzel’s computer program of negativity that keeps running without provocation. The “flaw in love” then becomes autonomous and self-fulfilling.
He proposes an alternative understanding of the role serotonin may play:
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.
This still doesn’t explain the variation in responses to psychotropics. He acknowledges as much and alludes to the need for new typologies of depression. (Remember the dark ages when we talked about endogenous vs. exogenous depressions?)
The layers of speculation can obscure or illuminate just how crude our understandings of depression and the brain are. This, along with the history of psychiatric fads and abuses, makes one wonder if we should proceed a little more cautiously and work a little harder to capitalize on non-pharmacological tools like exercise and social support.