[ufo]

IIRC, the current consensus among the psychiatric community is that SSRIs do work but no one actually knows what mechanism could explain their effectiveness. The one thing that is known for sure is that it doesn't come down to simply high vs low levels of serotonin because while SSRI treatment immediately raise serotonin levels the therapeutic effect takes some time to "kick in".

I also recall reading that SSRIs have been found to be more helpful against anxiety than depression.