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Breaking Down Heroin’s Effect on the Brain & Body

Heroin affects the brain by binding to opioid receptors, triggering a cascade of chemical reactions that result in intense euphoria, pain relief, and changes in cognitive function. In the body, heroin causes respiratory depression, gastrointestinal issues, cardiovascular changes, and immune system suppression.

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With prolonged use, the brain adapts to the presence of the drug, causing tolerance to and dependence on heroin to develop. This can lead to structural alterations in the brain, which in turn causes cognitive impairment and an exacerbation or instigation of underlying mental health disorders. 

The impact of heroin on both the brain and body can be life-altering and life-threatening. If you or someone you love is living with a heroin addiction, immediate detox via medication-assisted treatment and comprehensive therapy are needed. 

How Does Heroin Impact the Brain?

Heroin has a significant impact on the brain, causing changes in both physiology and function that can alter behavior, mental health, and physical health.[1] The drug binds to opioid receptors in the brain, triggering a domino effect of chemical reactions that cause the following:[1-3] 

Pain Relief

Heroin diminishes the perception of pain, providing a temporary escape from physical or emotional distress.

Dopamine Dump

Heroin triggers a surge of dopamine, a neurotransmitter that is associated with reward and pleasure, causing people to feel good when they use heroin This dopamine dump reinforces drug-seeking behavior and psychological dependence on the drug.

Development of Tolerance

With prolonged heroin use, the brain adapts by reducing its sensitivity to the drug. As a result, larger and larger doses are needed to reach the desired high.

Dependence & Withdrawal

Continued heroin use results in the brain’s dependence on the drug for normal functioning. Abruptly stopping or reducing heroin consumption triggers withdrawal symptoms that can be stressful, causing anxiety, restlessness, muscle pain, insomnia, gastrointestinal disturbances, and flu-like symptoms. 

Structural Modifications

Chronic heroin use can bring about structural changes in the brain. Studies reveal alterations in gray and white matter, particularly in parts of the brain that are responsible for making decisions, managing stress, and controlling impulsive behavior.

Cognitive Impairment

Long-term heroin use can cause cognitive dysfunction that is characterized by poor memory, inattention, and inability to make decisions. Even after discontinuing heroin use, these issues may continue, affecting daily functioning.

Impact on Mental Health

Heroin use increases the risk of developing or worsening mental health disorders like depression and anxiety.

Potential for Brain Damage

Heroin’s negative impact on the brain can ultimately add up to severe long-term damage. This happens for a number of reasons:[4-6] 

  • Heroin is a toxic substance that changes how the brain functions. Repeated exposure to this toxin means that some brain function may be lost for good. 
  • There are impurities in street heroin that can include substances added to it to make a batch go further or increase its potency. Any of these can have their own negative impact on the brain and cause damage, especially if it’s fentanyl, a potent opioid in its own right. 
  • Heroin use can lead to reduced oxygen supply to the brain, and oxygen deprivation causes brain damage. 
  • Cerebral edema, or swelling in the brain, can occur with heroin use as well. 
  • If a stroke occurs due to heroin use or overdose, disruption of blood supply to the brain can occur and cause brain damage. 

How Does Heroin Impact the Body?

Whether it is smoked, snorted, or injected, heroin moves quickly throughout the body once it enters the bloodstream, causing a number of negative changes to various organs and systems. These changes can include the following:[7-10]

CNS Depression

Heroin acts as a depressant on the central nervous system, inducing a state of sedation, which results in slowed brain activity, impaired reflexes, coordination difficulties, and reduced mental acuity.

Pain Relief & Accidents

Heroin is an opioid, and as such, it has analgesic properties, providing relief from physical pain. The lessening of the perception of pain signals can cause someone under the influence to get hurt and not realize it.

Gastrointestinal Distress

Heroin use can lead to gastrointestinal complications, such as constipation, slowing down the movement of the digestive tract just as it slows down and depresses other functions in the body.

Respiratory Suppression

The respiratory system is significantly suppressed when heroin is consumed. Breathing slows and gets shallow, potentially slowing down so much that respiratory failure occurs. Oxygen deprivation and life-threatening consequences can occur.

Cardiovascular Impact

Heroin affects heart rate and blood pressure. Initially, the heart rate may rise, but as the drug takes hold, it tends to decrease. At the same time, blood vessels may constrict and lower blood pressure, reducing blood flow to vital organs.

Skin Issues

Chronic heroin users may encounter skin problems due to injection-related complications. These can include infections, abscesses, or vein collapse. The urge to scratch or pick at the skin is likely due to itchiness caused by heroin use.

Disruption of the Endocrine System

Heroin abuse disrupts normal functioning of the endocrine system, which regulates hormone production. This disruption can result in hormonal imbalances, leading to issues such as menstrual irregularities in women and decreased libido in both men and women.

Suppression of the Immune System

Long-term heroin use weakens the immune system, making users more susceptible to infections and illnesses — both those related to heroin use and those caused by bacteria and viruses.

Nutritional Deficiencies

Heroin use often causes a diminished appetite and reduced food intake, potentially resulting in nutritional deficiencies. This can lead to weight loss, weakened immune function, and an overall decline in physical health.

Updated May 6, 2024
  1. Heroin. U.S. National Library of Medicine. Published 2018. Accessed November 30, 2023.
  2. Effect of heroin use on changes of brain functions as measured by functional magnetic resonance imaging, a systematic review. Fareed A, Kim J, Ketchen B, et al. Journal of Addictive Diseases. 2017;36(2):105-116.
  3. Chronic heroin use disorder and the brain: Current evidence and future implications. Tolomeo S, Steele JD, Ekhtiari H, Baldacchino A. Progress in Neuro-Psychopharmacology and Biological Psychiatry. 2021;111:110148.
  4. Research Report Series: Heroin. National Institute on Drug Abuse. Published November 2014. Accessed November 30, 2023.
  5. Delayed cerebral edema leading to cerebral hernia in a patient with heroin overdose. Amjad W, Qureshi WT, Farooq AU. American Journal of Therapeutics. 2018;25(6):e752-e755.
  6. Relationships between oxygen changes in the brain and periphery following physiological activation and the actions of heroin and cocaine. Thomas SA, Curay CM, Kiyatkin EA. Scientific Reports. 2021;11(1).
  7. Drug Fact Sheet: Heroin. Drug Enforcement Administration. Published April 2020. Accessed November 30, 2023.
  8. Understanding heroin overdose: A study of the acute respiratory depressant effects of injected pharmaceutical heroin. Jolley CJ, Bell J, Rafferty GF, Moxham J, Strang J. Fischer G, ed. PLOS ONE. 2015;10(10):e0140995.
  9. Opioids and endocrine dysfunction. Seyfried O, Hester J. British Journal of Pain. 2012;6(1):17-24.
  10. Opioid system modulates the immune function: A review. Liang X, Liu R, Chen C, Ji F, Li T. Translational Perioperative and Pain Medicine. 2016;1(1):5-13.
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