I mean, the often cited model of depression as a serotonin 'deficiency'--e.x. "I'm depressed because I don't have enough serotonin" is definitely not supported

I mean, the often cited model of depression as a serotonin 'deficiency'--e.x. "I'm depressed because I don't have enough serotonin" is definitely not supported by the science/literature that I'm familiar with. It does seem to have embedded itself in the popular mind, but if it was the case you would see patients with depression having abnormally low levels of serotonin, which isn't, to my knowledge, substantiated--the studies I've read didn't, as I recall, show a significant correlation between serum serotonin levels and mood. Low levels of serotonin do correlate with other things, though. (impulsivity, suicide risk) The serotonin system having an effect on mood, though, or SSRIs as treatments for depression: that's an entirely different realm. They do seem to be much less effective on people who are on the minor/moderate end of the spectrum, and are definitely less effective than they were once advertised as being. There are a lot of reasons (aforementioned side effects, effectiveness of various types of therapies, prevalence of environmental effects in many people's depression) to try other options than SSRIs if you aren't severely depressed--but the clinical evidence for their efficacy in treating severe depression isn't really arguable either. As a side note, there's some fairly recent research from the middle of last year (see these for the summary version: http://en.wikipedia.org/wiki/Tianeptine http://en.wikipedia.org/wiki/Tianeptine and http://en.wikipedia.org/wiki/Reuptake_enhancer http://en.wikipedia.org/wiki/Reuptake_enhancer) that shows that the only drug ever released as an SSRE probably isn't effective because of that action (if it even is an SSRE--see the second link).