Introduction
The widespread disturbances of monoamine neurotransmission that occur in depression are probably fundamental to its pathophysiology.1,2 More specifically, a deficiency in serotonin (5-HT), norepinephrine (NE), and possibly dopamine (DA) neurotransmission has been suggested.3,4 A relationship exists between the different neurotransmitter deficits and the symptoms of major depression.5 Depressed mood; loss of interest or pleasure; sleep disturbances; and feeling of worthlessness, pessimism, and anxiety are symptoms related to changes in both 5-HT and NE neurotransmission.5,6 Agitation, loss of appetite, decreased libido, suicidal ideation, aggressive behavior (verbal or physical), and irritability are symptoms related principally to the dysfunction of 5-HT neurotransmission.5,6 DA is important in the regulation of drive.7,8 Reduced noradrenergic activity is responsible for decreased concentration, mental and physical slowing, loss of energy, lassitude, tiredness, and reduced self-care.5,6