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Indiana Prevention Resource Center (IPRC)

Substance Use and the Brain

Dopamine is a brain chemical that produces a sensation of pleasure. It is what causes feelings of enjoyment when we see, taste, feel, hear, see or do something pleasurable. Anything from eating a favorite dessert to having a sexual orgasm leads to dopamine release. Even our thoughts and imagination can trigger dopamine in the brain – seeing that dessert in the bakery window or remembering a sexual encounter may be enough.

Source: http://bigthink.com/going-mental/your-brain-on-drugs-dopamine-and-addiction

Dopamine is nature’s way of ensuring that humans seek out and do those pleasurable acts that promote our own survival, and that of the species. Drugs and alcohol, however, also trigger dopamine release in the brain. This initial dopamine surge is so intensely pleasurable that the drug user is motivated to seek the drug out again. However, with continued use, the amount of pleasure decreases. In the past , people thought that persons addicted to a drug experienced more pleasure from that drug than persons not addicted to it. Now we know from research that an addicted person actually experiences less pleasure from the drug than the non-addicted person. At the same time, however, the addicted persons will experience more pleasure than would a non-addicted person from contextual triggers like being in a place with a drug dealer or a place where drugs were used.

Mental health is also related to dopamine release. Certain mental disorders are associated with lower dopamine release and hence an urge to seek more pleasure, creating a higher risk of drug use. (Volkow, 2015) Drug use and abuse are often co-occurring with mental and physical problems like depression or prolonged pain (Dept of VA, c2014).

Our brains are, by design, flexible and very adaptable. While this is good because it helps people adjust to changing circumstances, it can be very problematic when the brain adapts to unhealthy stimuli. In the case of drug use, it can reinforce a behavior that is pleasurable to the point of making the behavior so automatic that it becomes a habit. It is difficult then to break the cycle and change one’s behavior. Difficult, but not impossible. (MCTF, 2013)

Just as each individual is unique, so, too, is each brain. Hence the risk of addiction differs for different people. Genetic and environmental factors play a role in influencing risk of addiction. The genetic link has been confirmed with regard to nicotine addiction (NIDA, 2009a and 2009b) and alcohol (Bailey, et al, 2014) Researchers using twins to study a single or multiple variables have found that genetic factors can influence a person’s reactions, positive and negative, both across drugs and also drug-specific ally (Agrawal, et al, 2014). Twin studies have also found that an adolescent’s family environment including family smoking and/or drinking behaviors, are predictive of the child’s smoking and/or drinking behaviors in young adulthood. (Bailey, J.A., et al, 2014) To become addicted usually involve both a genetic tendency and environmental influences that encourage or allow the person to use a drug enough to become addicted. With more advanced understanding of DNA, researchers are discovering that genetics and epigenetics are involved. Epigenetics is said to “bridge the gap between nature and nurture” (Davis, n.d.)

...research into genetics and epigenetics is finally starting to shed some light on the causes of addiction. . . an enormous number of factors, ranging from early life trauma to genes that code for metabolic enzymes, have a role in how the genetics of addiction unfold. By understanding how these factors fit together, researchers hope to develop strategies for the prevention and treatment of addiction. (Szalavitz, 2015)

Psychological trauma can produce changes in the brain such as PTSD. Physical injury can also cause traumatic brain injury, which can be manifest in symptoms including sleep disorders and depression. These conditions can cause a person to derive less pleasure from everyday life and to seek more pleasure (dopamine release) through the use of drugs.

Just as mental health influences the brain’s dopamine release, general physical health, age and genetics play a role. The brain is more vulnerable to damage from drugs in the early years of life, when the body and brain are still developing.  Method and circumstances of administration and age of first use all play a role. The earlier in life a person begins to use an addictive drug, the more likely the person will become addicted, making youth the most vulnerable period. The effects of alcohol exposure on the fetus are a dramatic example in the form of fetal alcohol syndrome disorder (FASD). For older adults, changes in metabolism and risks of drug interaction influence how the drug impacts brain function, including balance and judgement.

Despite some differences between drugs, to a large extent, addictive drugs have similar effects on brain chemistry that can lead to addiction. (Nestler, 2013)  Still, different drugs have somewhat different effects, e.g., depressants (like alcohol, marijuana and heroin) versus stimulants (like cocaine and methamphetamine). Drug interactions, the results of consuming more than one drug at a time, are particularly dangerous as results can be unpredictable and far exceed in degree the consequence of taking the drugs independently.

Specific Drugs and the Brain:
Heroin, a drug of increasing concern in Indiana and elsewhere, holds a high risk of addiction. Heroin changes to morphine in the brain and binds to receptors in the brain stem, where blood pressure, respiration and arousal are controlled. Too much heroin in the person’s system – an overdose—can suppress breathing (called hypoxia). Hypoxia reduces the oxygen that enters the brain and can cause damage up to and including coma, permanent brain damage, and death. (NIDA, 2014a)

Inhalants have been long known to be capable of causing permanent brain damage. For adolescents, cognitive functioning and processing speed can be impacted, with earlier age of first use and amount of use being factors. (Scott, 2014)

Marijuana, especially when used heavily, has been found to alter brain structure and brain chemistry. (Volkow, 2014) There is controversy over the long-term impact of marijuana use on the brain, with recent back and forth acceptance and rejection of research findings over the past few months. The Journal of Addictive Behaviors, published by the American Psychological Association (APA), reported findings in the summer of 2015 that there is not a link between teenage marijuana use and mental and physical problems in adulthood.  In January 2016 they reversed their position, saying there is, indeed, a link to psychosis in adulthood -- followed by yet another reversal statement in February 2016, saying that no errors had been found in the original report. The debate continues. (Alcoholism & Drug Abuse Weekly, 2016)

Methamphetamine, for example, damages the dopamine receptors, breaking the usual replenishment of dopamine in the brain, causing a depletion of the chemical, so that the person’s ability to experience pleasure is severely reduced. Years of sobriety and healing are required before the person can experience normal pleasures again. In addition, the long half-life of the drug (the length of time it continues acting in the body after the initial ‘rush’) is very long, typically resulting in an extended high lasting about twelve hours, compared to cocaine’s half-life of 0.5-2 hours (Ciccarone, 2011). Chronic meth use causes chemical and molecular alterations in the brain, associated with decreased motor skills, learning skills, emotional and memory problems (NIDA, 2014b)

Fortunately, the brain has a great capacity for healing over time, and given enough time a person can retrain their brain to adapt to a healthier lifestyle and maintain sobriety in recovery. Some types of drug-related brain damage are, however, permanent.

Fetal Alcohol Syndrome Disorders:
One type of brain damage that does not heal over time is that due to fetal alcohol exposure. In the case of fetal alcohol syndrome disorder (FASD), the child’s brain is impacted before birth by the alcohol consumed by the mother during pregnancy. The most extreme cases include distinct facial features and developmental delays. Other children with more subtle brain damage are not diagnosed until adolescence, when the child is unable to function normally in school or in general society and exhibits deficiencies in executive function and/or moral judgement, such as an inability to distinguish right from wrong. In these cases early intervention and support services can make a big difference in the child’s outcome and success as an adult. (Andrew, et al, 2013).

Resources for Parents and Communities:
All of the online sources cited in this article, and score of additional resources on this topic are available at the IPRC HOME library for use in a campaign to educate your community about this topic. An example is the brochure for teens, Drugs: Shatter the Myths, that discusses how “the chemical structure of some drugs resembles natural brain chemicals” called neurotransmitters, how “drugs mess with your brain’s wiring and signals,” the differences between various drugs’ effects, how drugs affect each person differently, and how treatment and rehabilitation work and can help a person overcome the addiction. Another example is an entertaining and accessible YouTube presentation on “Brain Science & Society: Thinking about the Future” that features a Harvard professor, Steven Hyman, who describes how drug use affects the brain and leads to addiction, making a complex subject easy to understand.


Agrawal, Arpana, Pamela A. F. Madden, Kathleen K. Bucholz, Andres C. Heath, and Michael T. Lynskey. (2014) “Initial reactions to tobacco and cannabis smoking: a Twin Study,” Addiction 109/4:663-671. Retrieved from http://onlinelibrary.wiley.com/doi/10.1111/add.12449/pdf.

Alcoholism & Drug Abuse Weekly. (2016) “Journal recants on marijuana-psychosis link; oops, again,” 28/6 (Feb 8):5.

Andrew, Gail and Carmen Rasmussen. (2013) Diagnosis of FASD in the Adolescent Years.  Center for FASD Diagnosis, Training Education and Research, FAS Clinical Services, Glenrose Rehabilitation Hospital , Alberta Health Services, Canada. Retrieved from https://www.youtube.com/watch?v=Zi2AFzu9YCs

Bailey, J.A., D.R. Samek, M.A. Keyes, K.G. Hill, B.M. Hicks, M. McGue, W.G. Iacono, M. Epstein, R.F. Catalano, K.P. Haggerty, and J.D. Hawkins. (2014) “General and substance-specific predictors of young adults nicotine dependence, alcohol use disorder, and problem behavior: Replication in two samples.” Drug and Alcohol Dependence 138/ :161-168. Retrieved from http://www.sciencedirect.com/science/article/pii/S0376871614000787.

Ciccarone, Daniel. (2011) “Stimulant Abuse: Pharmacology, Cocaine, Methamphetamine, Treatment, Attempts at Pharmacotherapy,” Primary Care 38/1. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3056348/

Multijurisdictional Counterdrug Task Force. (2013) The Origins of Addiction. [Panelists from NIDA] Retrieved from http://mctft.org/training/the-origins-of-addiction/

Nestler, Eric. (2013) “Molecular Mechanisms of Drug Addiction.” Brain and Behavioral Research Foundation, Icahn School of Medicine, Mount Sinai. [webinar] Retrieved from https://www.youtube.com/watch?v=rlkD9kx-piw

National Institute on Drug Abuse (NIDA). (2014a) DrugFacts: Heroin. Retrieved from http://www.drugabuse.gov/publications/drugfacts/heroin

National Institute on Drug Abuse (NIDA). (2014) DrugFacts: Methamphetamine. Retrieved from http://www.drugabuse.gov/publications/drugfacts/methamphetamine

National Institute on Drug Abuse (NIDA). (2009a) “Ethnic Groups Have Contrasting Genetic Risks for Nicotine Addiction.” NIDA Notes. Retrieved from https://www.drugabuse.gov/news-events/nida-notes/2009/10/ethnic-groups-have-contrasting-genetic-risks-nicotine-addiction.

National Institute on Drug Abuse (NIDA). (2009a) “Studies link family of genes to nicotine addiction.” NIDA Notes 22/6. Retrieved from http://www.drugs.indiana.edu/repository/NNvol22N6.pdf

Scott, K.D. (2014) “Adolescent Inhalant Use and Executive Cognitive Functioning,” Child 40/1 (Jan). Retrieved from http://onlinelibrary.wiley.com/doi/10.1111/cch.12052/full

Szalavitz, Maia. (2015) “Genetics: No more addictive personality.” Nature 522/7557. Retrieved from


US Department of Veterans Affairs, Office of Research & Development. (c2014) VA research on substance use disorders. Retrieved from http://www.research.va.gov/topics/substance_abuse.cfm

Volkow, Nora. (2015) “Dr. Nora Volkow on Addiction: A Disease of Free Will,” NIDA. Retrieved from www.youtube.com/watch?v=X1AEvkWxbLE.

Volkow, Nora. (2014) NIDA’s Dr. Nora Volkow Discusses Marijuana’s Effects on the Brain, Body & Behavior. CADCA. Retrieved from https://www.youtube.com/watch?v=RSDnLSU3owc