First off, I'm very very ignorant of all this. Suck at science. I know the basic "key-lock" model of receptors and whatnot but really I'm pretty ignorant, so I apologize if this is a stupid question.
But yeah. Most antidepressants act by in some way increasing the amount of Serotonin in the brain (as well as, in many cases, Dopamine and Epinephrine). I understand that Serotonin is associated with feelings of euphoria and relaxation, Dopamine and Epinephrine with stimulation, a more excited euphoria, loss of appetite, etc. etc.
But how come antidepressants can cause a numb, empty feeling if they're increasing the levels of neurotransmitters that cause feelings of euphoria? I just really don't understand this. I mean, they basically do the same thing in your brain as drugs like Cocaine do - inhibiting the reuptake of those neurotransmitters - but, while they can sometimes cause feelings of euphoria and jitteriness, they also can cause a numb, empty, mildly euphoric but mostly emotionless feeling.
Why is this?