The field of psychopharmacology studies a wide range of substances with various types of psychoactive properties. The professional and commercial fields of pharmacology and psychopharmacology do not mainly focus on psychedelic or recreational drugs, as the majority of studies are conducted for the development, study, and use of drugs for the modification of behavior and the alleviation of symptoms, particularly in the treatment of mental disorders (psychiatric medication). While studies are conducted on all psychoactives by both fields, psychopharmacology focuses primarily on the psychoactive and chemical interactions with the brain.
Psychoactive drugs may originate from natural sources such as plants and animals, or from artificial sources such as chemical synthesis in the laboratory. These drugs interact with particular target sites or receptors found in the nervous system to induce widespread changes in physiological or psychological functions. The specific interaction between drugs and their receptors is referred to as "drug action", and the widespread changes in physiological or psychological function is referred to as "drug effect".
The common muscimol-bearing mushroom Amanita muscaria, also known as the "Fly Agaric", is frequently regarded as one of the first used psychoactive drugs, it is suspected to be the primary or active ingredient in the sacred drug of ancient India, known as Soma. There are many modern theories citing the discovery of its psychoactive properties as far back as 10,000 BCE.
With the dawn of the Neolithic and the proliferation of agriculture, new entheogens came into use as a natural by-product of farming. Among them were opium, cannabis, and alcohol derived from the fermentation of cereals and fruits. Most societies began developing herblores, lists of herbs which were good for treating various physical and mental ailments. For example, St. John's Wort was traditionally prescribed in parts of Europe for depression (in addition to use as a general-purpose tea), and Chinese medicine developed elaborate lists of herbs and preparations.
With the scientific revolution in Europe and the United States, the use of traditional herbal remedies fell out of favor with the mainstream medical establishment, although a few people continued to use and maintain knowledge of traditional European herblore. In the early 20th century, scientists began reassessing this rejection of traditional herbs in medicine. A number of important psychiatric drugs have been developed as a by-product of the analysis of organic compounds present in traditional herbal remedies. In the latter half of the 20th century, research into new psychopharmacologic drugs exploded, with many new drugs being discovered, created, and tested. Many once-popular drugs are now out of favor, and there are fashions in psychiatric drugs, as with any other kind of drug.
Only since the 1950s has the use of psychiatric drugs to restore mental health, or at least limit aberrant behavior, been a part of medical therapeutics, when a number of new classes of pharmacological agents were discovered, notably tranquillizers (e.g., chlorpromazine, reserpine, and other milder agents) and antidepressants (including the highly effective group known as tricyclic antidepressants), and LSD was popularized among many psychiatrists for a certain time as a mental miracle drug capable of curing all manner of problems. Lithium is widely used to allay the symptoms of affective disorders and especially to prevent recurrences of both the manic and the depressed episodes in manic-depressive individuals. The many commercially marketed antipsychotic agents (including thiothixene, chlorpromazine, haloperidol, and thioridazine) all share the common property of blocking the dopamine receptors in the brain. (Dopamine acts to help transmit nerve impulses in the brain.) Since scientists have found a direct relationship between dopamine blockage and reduction of schizophrenic symptoms, many believe that schizophrenia may be related to excess dopamine.
These drugs contrast sharply with the hypnotic and sedative drugs that formerly were in use and that clouded the patient's consciousness and impaired his/her motor and perceptual abilities. The antipsychotic drugs can allay the symptoms of anxiety and reduce agitation, delusions, and hallucinations, and the antidepressants lift spirits and quell suicidal impulses. The heavy prescription use of drugs to reduce agitation and quell anxiety has led, however, to what many psychiatrists consider an overuse of such medications. An overdose of a tranquilizer may cause loss of muscular coordination and slowing of reflexes, and prolonged use can lead to addiction. Toxic side effects such as jaundice psychoses, dependency, or a reaction similar to Parkinson's disease may develop. The drugs may produce other minor symptoms (e.g., heart palpitations, rapid pulse, sweating) because of their action on the autonomic nervous system.
Clinical studies are often very specific, typically beginning with animal testing, and ending with human testing. In the human testing phase, there is often a group of subjects, one group is given a placebo, and the other is administered a carefully measured therapeutic dose of the drug in question. After all of the testing is completed, the drug is proposed to the concerned regulatory authority (e.g. the U.S. FDA), and is either commercially introduced to the public, introduced to the public via prescription, or deemed safe enough for over the counter sale.
Though particular drugs are prescribed for specific symptoms or syndromes, they are usually not specific to the treatment of any single mental disorder. Because of their ability to modify the behavior of even the most disturbed patients, the antipsychotic, antianxiety, and antidepressant agents have greatly affected the management of the hospitalized mentally ill, enabling hospital staff to devote more of their attention to therapeutic efforts and enabling many patients to lead relatively normal lives outside of the hospital. A somewhat controversial application of psychopharmacology is "cosmetic psychiatry" Persons who do not meet criteria for any psychiatric disorder are nevertheless presribed psychotropic medication. The antidepressant Wellbutrin is then prescribed to increase perceived energy levels and assertiveness while diminishing the need for sleep. The antihypertensive compound Inderal is sometimes chosen to eliminate the discomfort of day-to-day "normal" anxiety . Prozac in nondepressed people can produce a feeling of generalized well-being. Mirapex, a treatment for restless leg syndeome can dramatically increase libido in women. These and other off-label life-style applications of medications are not uncommon. Although occasionally reported in the medical literature no guidelines for such usage have been developed.