Clinical depression is an insidious and pernicious mental disorder - mental condition - affecting millions of persons globally and in the U.S. Depression is a physical mental condition interfering with everyday life. Physical because it occurs as changes in neuro-transmitters in the brain take place; and mental because changes in neuro-transmitters may lead to changes in mental mood and behavior without apparent reasons. A neuro-transmitter is defined as 'chemical' substance produced within the brain for the purpose of establishing normal communication between neurons, the cells that regulate mental activity in the brain. At a simplified explanation, chemical substances ferrying information from neuron to neuron (cells within the brain) become unable of such function for unknown reasons.