Many drugs— including the SSRI antidepressants such as Prozac, and stimulant medications—work directly or indirectly by altering levels of neurotransmitters, the chemical messengers in the brain. They may activate or inhibit the release of various neurotransmitters or block their reuptake in the nervous system, which increases their availability and beefs up their signaling power.Psychopharmacology is the scientific study of the effects drugs have on mood, sensation, thinking, and behavior. It is distinguished from neuropsychopharmacology, which emphasizes the correlation between drug-induced changes in the functioning of cells in the nervous system and changes in consciousness and behavior.Psychopharmacology is the study of the use of medications in treating mental disorders. The complexity of this field requires continuous study in order to keep current with new advances. Psychopharmacologists need to understand all the clinically relevant principles of pharmacokinetics (what the body does to medication) and pharmacodynamics (what the medications do to the body). This includes an understanding of