Psychotropic drugs, sometimes also called psychoactive, affect the central nervous system, and can cause a variety of changes in behavior or perception. Many think psychotropic drugs are only of the illegal variety, like the psychedelic drugs frequently used in the late 1960s, such as LSD, angel dust, and marijuana. However, even something as relatively benign as caffeine is considered one of many psychotropic drugs.

Psychotropic drugs have different uses and are broken into four major groups: hallucinogens, antipsychotics, depressants and stimulants. Types often cross into other categories as they produce more than one type of effect. Marijuana, for example is considered a depressant, stimulant and hallucinogen.

Marijuana has many applications in medicine and may be helpful to some patients with AIDS or cancer. Since marijuana can control nausea and promote appetite, as well as reduce pain, it can be helpful for those experiencing intense suffering. However, stigma associated with illegal marijuana use by hippies has stalled legalization, or limited access to the drug for medicinal purposes for many.

Another of the psychotropic drugs frequently in use is alcohol, a depressant. It can impair mood, causing either elation or depression, and impairs ability to think clearly or make rational decisions. Supporters for legalization of marijuana often point to the oft-used and readily available alcohol that is considered far more toxic, potentially impairing and dangerous, as well as addictive, compared to marijuana.

Other psychotropic drugs effecting mood include antidepressants, antipsychotics, mood stabilizers and tranquilizers. The various effects of these psychotropic drugs are considered vital to the practice of psychiatry. Antidepressants like Prozac®, and Zoloft® may help reduce depression or anxiety. They can however, provoke anxiety as they are of the stimulant type. Tranquilizers, which are of the depressant class, may be more effective for severe anxiety. Mood stabilizers may either be of the stimulant or antipsychotic class and can help people with bipolar conditions. Anti-psychotics are often used to treat schizophrenia.

Some psychotropic drugs can foster addiction, with many belonging to either the stimulant or depressant classes. For example, many depressants like morphine are used to alleviate symptoms of pain. Morphine is addictive, and is derived from opium, from which heroin is also derived. Most receiving morphine also note hallucinatory episodes when given high doses of morphine, and long term use of morphine can cause difficulties in withdrawing from the medication.

Stimulants, which can range from caffeine, to Ritalin, to illegal medications like crystal meth, crank and cocaine also can be addictive. For example, coffee drinkers may notice extreme headaches if they skip a day of drinking coffee. The headache can be severe but tends to resolve in a day or two. Nicotine is a highly addictive stimulant, though most people believe it has a relaxing effect. Addiction to cocaine is almost assured after consistent use over several weeks. As well, children who take Ritalin can become dependent upon the medication and have a difficult time weaning off of it as adults.

The action of psychotropic drugs is not always clearly understood. For example, researchers assume some antidepressants increase the levels of serotonin in the brain. This is theory, and those using the medications seem to benefit. However, it is not proof, and little explanation exists for those who have opposite reactions to medications used to elevate mood. As well, nicotine is thought to both relax and stimulate, another unclear reaction.