Chronic use of heroin can lead to changes in the neural pathways of the brain that can result in issues with normal functioning. Heroin use also damages the brain through several other mechanisms.
Heroin is a controlled substance listed by the U.S. Drug Enforcement Administration (DEA) in the Schedule I classification. This means it is deemed to have no useful medical purposes and cannot be possessed by private individuals for any reason unless they have special permission from the government. Usually, permission is given for recognized research institutions that study the effects of drugs.
It is typically sold as a white or brownish powder that is often cut with other substances, such as powdered milk, starch, quinine, or other drugs.
Today, pure heroin that may be seized in drug busts in the United States most often comes from South America instead of Asia. The heroin referred to as “black tar” heroin is most often produced in Mexico and is considered to be less pure than white heroin.
The heroin epidemic in the U.S. occurred in the late 1950s and early 1960s. It was mostly brought under control by authorities.
Recently, the opioid epidemic that resulted in tighter controls on prescription opioid drugs led to a reemergence of heroin abuse by street users.
Heroin is an opioid drug, meaning it is derived from opium. When a person takes heroin, it is converted into morphine in the body, and then it binds to receptors in the brain that are called mu–opioid receptors (often referred to as endogenous opioid receptors).
Certain neurotransmitters that regulate feelings of stress, pain, the release of hormones, and other feelings are specialized for these receptor sites, and heroin binds to the sites readily. When these sites are activated, they stimulate other areas in the brain, such as the reward center, causing a release of the neurotransmitter dopamine. This leads to feelings of reinforcement, satisfaction, and similar positive experiences.
The personal experience of using heroin will vary among individuals. It can depend on numerous factors that include:
Heroin users report a surge of pleasure or feeling of reward, often referred to as “the rush,” when they use the drug. This surge of euphoria is typically followed by a warm feeling or flushing of the skin, dryness in the mouth, feelings of relaxation, and a heavy feeling in the arms and legs. Other effects including itching, nausea, significantly decreased mental functions, decreased heart rate, slowed breathing, and other reduced body functions.
Heroin is most often snorted, smoked, or injected. These means of administration allow for rapid absorption of heroin into the system.
The brain naturally changes in response to experience. This adaptability of the brain is often referred to as neuroplasticity.
Repeatedly using any drug will result in changes in the structure and function of certain areas of the brain. Technically, these changes are not considered brain damage as they are the result of the brain’s natural ability to adapt itself to the environment.
However, chronic use of drugs like heroin produces changes in the brain that are the result of neuroplasticity, which later lead to dysfunctional behaviors or outcomes. Thus, the changes that occur in the brain associated with repeated drug use are often considered to be neurodegenerative.
Heroin use can also lead to tissue damage in the brain and other organs.
Chronic abuse of heroin can lead to tissue damage in the brain through several potential mechanisms.
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Repeated use of opioids like heroin changes the physical structure of the brain. This can lead to long-term imbalances in neurotransmitters and hormones that may not fully resolve even if the individual stops using heroin. The various types of brain changes are outlined below.
A study in the journal Neuropathology and Applied Neurobiology examined the brains of chronic methadone and heroin users who died. The average age at death was 26, indicating that these individuals should have relatively normal brain development.
The findings of the study indicated that people who had chronically abused opioids like heroin were three times more likely to have changes in the brain that resembled Alzheimer’s disease. The changes occurred in the white matter of the brain (the signaling portions of neurons).
The alterations occurred due to the development of proteins in the brain. This is more often associated with people who have been diagnosed with Alzheimer’s disease.
Chronic use of heroin leads to a cycle of massive increases in the neurotransmitter dopamine. This increase is followed by a depletion of dopamine in the brain when the person stops using the drug.
These changes occur in an area of the brain that is often referred to as the reward system. The system is designed to ensure that behaviors that are proactive and reinforcing have a greater chance of being repeated, and activities that result in negative consequences have a greater chance of not being repeated.
Chronic heroin use stimulates the feeling of reinforcement. This increases the probability that the individual will continue using heroin due to these changes in the brain.
Tolerance is a complex physiological and psychological phenomenon that is the result of the repeated use of a drug.
Repeated heroin use increases neurotransmitters in the brain like dopamine, which is associated with the drug’s pleasurable effects. The natural tendency is for the system to try to maintain a balance (homeostasis) of neurotransmitters and hormones.
When certain neurotransmitters are increased repeatedly, the system will automatically increase the levels of hormones and neurotransmitters that produce the opposite effects. Over time, the system resets, and the person needs more of the drug to get the same effect they once got. This is tolerance.
Over time, these changes result in the individual having difficulty experiencing pleasure and reinforcement through everyday activities. They are more likely to experience negative feelings like irritability, discomfort, and chronic feelings of emotional distress as their natural state. This leads to increased use of heroin to avoid these negative states.
The development of significant tolerance to heroin is a sign that the person is on the road to developing a physical dependence on the drug.
Physical dependence to any substance, including heroin, is a direct result of the changes the system made to accommodate for the presence of the drug. This includes changes that are made to the brain.
The system is thrown out of balance when levels of heroin are decreased. This leads to an increase in feelings that are often opposite to what the drug produces. In the case of heroin, these feelings include:
For many chronic users, using heroin becomes their primary goal in life.
The limbic system is an area of the brain that has numerous functions.
It contributes to the experience of emotions and the development of memories that are associated with different emotional states.
Chronic use of heroin alters the circuits in the limbic system, which can lead to later problems with emotional regulation. Individuals who are chronic heroin users often become impulsive and have uncontrollable emotional reactions to seemingly trivial events.
At other times, they appear to have no concern over events that are obviously threatening.
Chronic use of opioids like heroin affects the neural pathways in the anterior portion of the brain — an area of the brain that is associated with higher intellectual capacities, including judgment, abstract thinking, and rationality.
These alterations result in individuals becoming less prone to thinking things through and more prone to immediately acting out in situations that are emotionally disturbed. They may have difficulty thinking in abstract terms. They may also have problems with rational thinking and judgment that would be considered to fall into the domain of “common sense.”
Chronic use of heroin can lead to alterations in areas of the brain that are important in learning and memory.
Respiratory suppression associated with chronic heroin use can result in changes and even damage to an area of the brain known as the hippocampus. This is a crucial area of the brain that is associated with learning new information and forming new memories.
Chronic heroin abuse can affect several areas of the brain that are associated with the ability to produce voluntary movements or goal-directed behaviors. Many of these areas are in the interior portions of the brain, but they are also present in the posterior portion of the brain known as the cerebellum.
Chronic opioid abuse can damage these areas and result in problems with coordinating movement, fine motor control, and even broader problems, such as issues with walking.
Chronic use of any opioid drug, including heroin, results in the blockage of messages from the body to the brain through the spinal cord, particularly messages associated with the experience of physical pain or stress.
When an individual uses an opioid, their sensation or perception of pain is dampened. When chronic abusers are not using these drugs, they may actually become more sensitive to feelings of pain and discomfort as a result of mechanisms described earlier (issues with tolerance and changes in brain pathways). This can result in increased use of heroin to cope with everyday issues. These issues may be somewhat uncomfortable to the average person, but they are experienced as painful to these individuals.
Although chronic use of heroin primarily affects certain brain pathways and neurotransmitter systems, other effects occur throughout the brain. Numerous potential issues can occur in individuals as a result of chronic heroin abuse.
According to the book Drugs, Addiction, and the Brain, some of these can include:
Chronic abuse of heroin can lead to many changes in the brain that can result in tissue damage and alterations in the functioning and structure of the brain. Other events associated with heroin use can damage the brain or change the structure of certain areas of the brain.
In some cases, these alterations may not be fully reversible, such as in cases where the brain damage from heroin resembles Alzheimer’s disease.
The only way to assuredly avoid the potential effects of heroin use on the brain is to stop using it. Since heroin is a serious drug of abuse, professional help is needed to treat the addiction. Treatment will start with medical detox to safely stop use of the drug and proceed to comprehensive therapy.
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(March 2018). Cerebral Hypoxia. National Library of Medicine. Retrieved from https://medlineplus.gov/ency/article/001435.htm
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