Dopamine is a neurotransmitter found in the brain that is often affected by drug use. Many different types of drugs, including cocaine and amphetamines, produce huge increases in dopamine levels in the brain. This spike in dopamine causes significant changes in the brain and body. Additionally, unnaturally high levels of dopamine are linked to mental and speech disorders.
Exhilaration
Dopamine is a central player in the brain's reward system and is heavily involved in the experience of pleasure. When dopamine levels are increased, the pleasure sensation is overloaded, and a person feels an intense sense of exhilaration, known as a "high."
Anxiety/Nervousness
After the initial high resulting from exposure to a large amount of dopamine ends, the brain and body remain in a heightened state of alertness. This state of alertness leads to feelings of irritability, nervousness and paranoia. Chronic exposure to high levels of dopamine can lead to outbursts of violent behavior and a psychosis similar to schizophrenia, according to the Center for Substance Abuse Research.
Depression
After a high dose of dopamine wears off and the brain and body relax from the heightened state of alertness, depression often results, reports the Center for Substance Abuse Research.
Tolerance
A single exposure to high levels of dopamine causes the brain to become less sensitive to dopamine, which is a process known as tolerance. Two changes take place in the brain. First, the receptors that are activated by dopamine become less reactive to the chemical. Second, the number of dopamine receptors decreases. As a result, the same levels of dopamine produce a smaller effect. Repeated exposure to high levels of dopamine increases the tolerance effect.
Addiction
Because dopamine is involved in the brain's pleasure center, the euphoric rush produced by dopamine has an addictive effect. The brain and the body associate pleasurable feelings with the behavior that caused the increase in dopamine, which often results in people seeking to repeat the behavior. The more times the pattern of behavior and reward is repeated, the stronger the addition grows.
Schizophrenia
The mental disorder schizophrenia has afflicted humankind for thousands of years, yet the exact cause is unknown. Several lines of evidence point to a role of dopamine in development of the disorder. According to the "dopamine theory of schizophrenia," high levels of dopamine and an overactive dopamine system cause the destructive behaviors associated with schizophrenia.
Stuttering/Tourette Syndrome
Recent research has suggested a role for dopamine in stuttering and Tourette syndrome. People who stutter often have greatly increased levels of dopamine in the brain. Furthermore, treatment with dopamine-blocking medications often reduces stuttering.
References
- Center for Substance Abuse Research: Methamphetamine
- University of Texas at Austin Science Research and Education Center: Dopamine
- National Institute on Drug Abuse: Understanding Drug Abuse and Addiction
- The National Academy of Sciences: Schizophrenia: More Dopamine, More D2 Receptors
- Minnesota State University: Serotonin-Dopamine Antagonists in the Treatment of Stuttering
