A new study suggests that Paxil doesn't directly effect mood, it instead changes the personality:
In case you were wondering, "neuroticism" is defined here as "a tendency to experience negative emotions and emotional instability," and since depression strikes me as a rather important "negative emotion," these aren't exactly independent variables. I find this study interesting mainly because, as I said, nobody knows how or why anti-depressants work, whichmakes any clue intriguing. One thing we do know is that low serotonin levels do not cause depression and are not even strongly correlated with it, so these drugs don't work by raising serotonin levels, at least not in any simple sense.
Medications frequently prescribed for depression may not lighten a person’s mood until they brighten his or her personality. A new study suggests that the antidepressant medication paroxetine, or Paxil, fights depression most effectively when it first modifies two personality traits that predispose people to this mood disorder.
The two traits, high neuroticism and low extraversion, have already been linked to depression. Depressed patients taking Paxil reported much greater change in these traits, as assessed via scores on personality tests, than patients given placebo pills. The difference was notable even after accounting for the extent to which each treatment diminished standard measures of depression, says psychologist Tony Tang of Northwestern University in Evanston, Ill. Patients who experienced especially pronounced personality change during four months of Paxil treatment displayed a particularly low depression relapse rate over the next year of treatment, Tang’s team reports in the December Archives of General Psychiatry.
“We propose that modern antidepressants work partly by correcting the long-term personality risk factors for depression,” Tang says.