The Brains of Addicts

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  1. Basic Definitions
  2.  Alcohol and the Brain
  3. Heroin and the Brain
  4. Cocaine and the Brain
  5. Methamphetamine and the Brain
  6. Summary: How Drugs Affect the Brain
  7. Finding Addiction Treatment

How Do Drugs Affect the Brain?

You have probably already made an intuitive assumption that drug use negatively impacts your brain. You're right. But how exactly does it affect the brain and behavior? Below is a summary of select research on how alcohol, heroin, cocaine, and methamphetamine affect particular brain regions and their associated behaviors.
How Do Drugs Affect the Brain?

Basic Definitions

First, it will be helpful to define some important terms:

  • Gray matter: the cell bodies of neurons and their surrounding "glia" (supporting cells). Scientists usually care about the density of gray matter within certain regions of the brain. Deteriorating gray matter is a sign that a particular region (and its associated general function) is declining.
  • White matter: the axons (covered in white "myelin") that connect to other areas of the brain, allowing for communication between regions. White matter is extremely important for many aspects of healthy brain and behavioral functioning.
  • Other regions such as the insula, hippocampus, and frontal and parietal lobes will be discussed. An explanation of their functions will be provided under each term.

White matter vs. Gray matter


 Alcohol and the Brain

Neuroimaging studies have revealed the following about the brain's of alcoholics1,2,3,4:

  • Reduction in white matter throughout the brain.
  • Damage to white matter appears to happen during alcohol consumption, not the withdrawal or recovery period.
    • In fact, it appears as though the brain will begin to heal itself during the recovery phase.
  • The more time someone spends being abstinent from alcohol, the better their integrity of white matter.
    • The time spent in abstinence may be an even more important variable than the duration of time or the quantity that someone has drank.
  • Within several months of recovery, alcohol abusers can begin to recover lost memory functions and prevent, or reverse, loss of white matter.
    • In one study, those that remained abstinent in the year following treatment had more white matter than those who relapsed.

Heroin and the Brain

Those who abuse heroin display the following characteristics in the brain5:

  • Overall, there is more damage to white matter.  
  • Reduced white matter connections between limbic structures and frontal association areas.
    • Limbic structures include the amygdala, hippocampus, fornix, and mammillary bodies. They are generally important for emotion, memory, motivation, and learning.
    • Frontal association areas are important for higher-level functioning, like attention, planning, impulse control, and regulating our emotions.
  • The longer someone uses heroin, the more white matter reductions in the left cingulate gyrus. Longer abstinence is associated with better white matter integrity in this region.
    • The cingulate cortex is connected to limbic and frontal areas, making it a part of the reward pathway (which largely motivates addictive behavior). Reduced connectivity implies less self-control and increased craving.

Limbic and frontal areas_MRI

Frontal and limbic areas_cartoon

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Cocaine and the Brain

Cocaine abusers show the following neurological deficits6:

  • Reduced gray matter in the right insula and right inferior frontal gyrus.
    • The insula, the right in particular, is responsible for our sense of being in our bodies, and other social and emotional processes.
      • The insula has been connected to addictive behaviors.It may be important for the ability to discriminate between choices that will lead to positive versus negative outcomes.8
    • The inferior frontal gyrus is important in language processing, inhibition, and impulse control.

Insula and IFG

Insula and IFG_Cartoon

Methamphetamine and the Brain

Neuroimaging analyses have revealed the following characteristics about methamphetamine users6,9:

  • Reduced gray matter in the insula and right inferior parietal gyrus.
    • The insula is important for body awareness, social, and emotional functions, and may be involved in addictions and positive decision making.
    • The more abstinence one has, the less of a reduction in the insula and right inferior parietal gyrus.
  • Meth users have 7.8% smaller hippocampal volumes. These reductions are correlated with deficits in memory.
  • Meth users show damage to the cingulate cortex, which is involved in the regulation of emotions, motivation, inhibition, and learning from previous behaviors.


Summary: How Drugs Affect the Brain

The research clearly demonstrates that individuals who abuse alcohol, heroin, cocaine, meth, and likely other drugs, have significant impairments to the integrity of their brain. Not only do certain structures begin to deteriorate, but their connections to other regions also die. This leads to changes in cognition and behavior that will ultimately affect many facets of life: work, relationships, mood, and daily activities. More information on the psychological and medical effects of drug use can be found in the Drug Abuse and Addiction section.

The fascinating thing about the research is that it may be possible to stop or reverse damage that has already been done. This tells us that it is never too late to make a healthy change in one's life. Your brain will respond to the choices you make.

Finding Addiction Treatment

If you are seeking treatment for substance abuse, you may want to consider:

  • Outpatient options: SAMHSA has an excellent treatment-finding tool for addiction-related treatment in your area.
  • Inpatient options: call 1-888-993-3112Who Answers? to learn about inpatient detox, treatment, and recovery centers.
  • Search for a nearby 12-step or other (e.g., "self-empowerment" or secular) group in your area using our "Find a Meeting" tool or through an internet search.
  • Consider contacting your insurance provider to learn about treatment options in your area.


  1. Monnig, M. A., Tonigan, J. S., Yeo, R. A., Thoma, R. J., & McCrady, B. S. (2013). White matter volume in alcohol use disorders: a meta‐analysis.Addiction biology, 18(3), 581-592.
  2. Zahr, N. M., Mayer, D., Rohlfing, T., Hasak, M. P., Hsu, O., Vinco, S., ... & Pfefferbaum, A. (2010). Brain injury and recovery following binge ethanol: evidence from in vivo magnetic resonance spectroscopy. Biological psychiatry, 67(9), 846-854.
  3. Sullivan, E. V. (2000). Human brain vulnerability to alcoholism: Evidence from neuroimaging studies. Review of NIAAA's Neuroscience and Behavioral Research Portfolio, NIAAA Research Monograph, (34), 473-508.
  4. Cardenas, V. A., Durazzo, T. C., Gazdzinski, S., Mon, A., Studholme, C., & Meyerhoff, D. J. (2011). Brain morphology at entry into treatment for alcohol dependence is related to relapse propensity. Biological psychiatry, 70(6), 561-567.
  5. Wollman, S. C., Alhassoon, O. M., Stern, M. J., Hall, M. G., Rompogren, J., Kimmel, C. L., & Perez-Figueroa, A. M. (2015). White matter abnormalities in long-term heroin users: a preliminary neuroimaging meta-analysis. The American journal of drug and alcohol abuse, 41(2), 133-138.
  6. Hall, M. G., Alhassoon, O. M., Stern, M. J., Wollman, S. C., Kimmel, C. L., Perez-Figueroa, A., & Radua, J. (2015). Gray matter abnormalities in cocaine versus methamphetamine-dependent patients: a neuroimaging meta-analysis. The American Journal of Drug and Alcohol Abuse, 41(4), 290-299.
  7. Nasir H. Naqvi, David Rudrauf, Hanna Damasio, Antoine Bechara. (January 2007). "Damage to the Insula Disrupts Addiction to Cigarette Smoking" (abstract). Science 315 (5811): 531–4.
  8. Paulus MP, Feinstein JS, Leland D, Simmons AN. Superior temporal gyrus and insula provide response and outcome-dependent information during assessment and action selection in a decision-making situation. NeuroImage 2005;25:607–615.
  9. Thompson, P. M., Hayashi, K. M., Simon, S. L., Geaga, J. A., Hong, M. S., Sui, Y., ... & London, E. D. (2004). Structural abnormalities in the brains of human subjects who use methamphetamine. The Journal of neuroscience,24(26), 6028-6036.

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