Pharmacology of antidepressants

The pharmacology of antidepressants is not entirely clear. The earliest and probably most popular scientific theory of antidepressant action is the monoamine hypothesis (which can be traced back to the 1950s), which states that depression is due to an imbalance (most often a deficiency) of the monoamine neurotransmitters (namely serotonin, norepinephrine and dopamine).