Over the last 20 years heroin addiction has rocketed into the national spotlight as one of the leading causes of preventable death in the United States. In this article we take a detailed look at how heroin affects the mind and body immediately upon using it.
How Heroin Affects The Brain
Heroin’s most potent effects are produced through hijacking the opioid system in the brain. This system is used to mediate pain, reduce depression and anxiety, and produce behavior related feelings of reward. Our bodies make natural chemicals which stimulate this system known as “endogenous” opioid peptides. Some of these endogenous opioids include the enkephalins, beta-endorphin, and dynorphin. Heroin acts on some of the same receptors as these peptides, however heroin has a much stronger binding affinity, meaning that it will activate the receptors much more strongly and for much longer than the endogenous peptides¹.
This mechanism of action has very far reaching effects throughout the brain and body by affecting both ascending and descending nerve pathways. Ascending nerve pathways take sensory information from the body to the brain. Descending pathways are the reverse, and involve signals from the brain to the body and include heart rate regulation, GI muscle control for digestion, and breathing among many others. Aside from nerve signalling to and from the brain, nerve function within the brain is also affected. Chronic heroin use can lead to increased tolerance through downregulation. Likewise, the limbic system, or “reward center” of the brain is also strongly affected, mostly through μ-opioid receptor overstimulation¹. This is shown to lead to an increase in reward seeking or addictive behavior.
When heroin is present in the brain, the body will respond by decreasing production of natural opioids. Once heroin has been used for an extended time, usually about 3 to 4 weeks, the brain will begin adapting by decreasing production of natural opioid peptides by a substantial amount. This means that the brain will be unstable without the continued presence of the exogenous (introduced from outside the body) opioids provided by continued heroin use. This has the effect of creating chemical dependence. Without continued introduction of exogenous opioids, you will begin to go into heroin withdrawal.
Because of the widespread effects of heroin use on the brain and subsequent behavior, let’s take a look at each area of perception that is effected:
The most potent effect of heroin is on the perception of pain through stimulation of the μ and δ opioid receptors in the brain. Through heroin use the sensation of pain can be severely dulled or even removed entirely. This effect is produced through interaction of ascending nerve pathways and also involves GABA, an inhibitory neurotransmitter. Heroin use will increase GABA activity in ascending pathways which has the effect of slowing and dulling the nerve signals before they even reach the brain. This means that any sensation of pain or discomfort will be weakened, or not even perceived at all¹.
Another effect is on temperature perception. This is produced through the same mechanism but is manifested differently. Heroin users often describe being high as if they were wrapped in a warm blanket. The sensation of cold, or temperature related discomfort is almost totally absent while high on heroin. There is also a total relaxation of both voluntary and skeletal muscles which amplifies the warm and relaxed sensation.
Due to heroin use thought is slowed or clouded dramatically and users tend to “nod off” or briefly lose consciousness and can have very vivid dreams during these episodes. When talking to a heroin user, they may nod off mid conversation and reply several seconds or minutes later as if nothing happened.
Heroin also has the very strong effect of suppressing negative emotions as well as producing positive feelings. This is achieved mainly through interactions at the κ and μ opioid receptors. Feelings of anxiety or depression are decreased or eliminated entirely while simultaneously a great sensation of wellness, security, and peace is produced. Once the brain has adapted to this state, removing heroin will have the opposite effect and these feelings will strongly rebound and increase depression and anxiety well above their pre-heroin levels¹.
Due to the emotional suppression of heroin, especially negative emotions, there is a decreased ability to process or deal with emotions in general by heroin users. This results in heroin users only feeling “ok” emotionally when they are high, or even that emotions are useless and must be avoided. Aside from reinforcing heroin use, this can later lead to emotional disorders which may persist long after heroin withdrawal has been completed.
While heroin increases GABA in ascending nerve pathways it also paradoxically reduces GABA production in the limbic system. This results in a surge of dopamine which produces strong feelings of pleasure and reward. This process is also responsible for feelings of anxiety, depression, and cravings for heroin when use is stopped¹.
Since heroin can reduce all emotions, there is a tendency for heroin addicts to exhibit antisocial tendencies. The perceived lack of feelings by a heroin user will decrease their ability to empathize with others. This has a doubly negative impact on an addict. It will make it easier to harm or rob others in the pursuit of heroin and likewise make it more difficult to ask for help, or to realize that they need help in the first place. This lack of empathy will make previously unacceptable behavior seem less wrong and this trend can escalate the longer heroin is used¹.
Likewise, the priorities of a heroin addict will change the deeper into addiction they go. With a fixation on doing heroin, many other things which used to be important will slide down the priority scale. Personal hygiene, social life, family, work, and hobbies will all become less and less important over time as the desire for heroin grows. Relationships begin to fall apart when getting high looks more appealing than spending time with friends or family. Subsequently, personal hygiene seems less important when you don’t have anyone left in your life and when it doesn’t help you getting more heroin. People may even choose to not eat so they can use that money for heroin, or the fact that less food in their stomach might mean they get a little more high. Finally, heroin may take priority over a place to sleep and someone will choose to be homeless so they can keep getting high. When heroin is the only thing that makes life okay, there is no limit to what an addict will sacrifice to get more.
How Heroin Affects The Body
Heroin affects a wide variety of systems in the body. The effects are depressive in nature meaning that everything gets slowed down to different degrees. The peripheral nervous system gets severely depressed and is responsible for keeping us alive through breathing, blood flow, and digestion. Since the depression is variable depending on the system affected, let’s look at each in turn:
Heroin produces several effects on the heart and circulatory system. Heart rate slows which lessens the speed that blood will circulate and replenish oxygen or remove waste. This has a cascade on all other vital functions, as oxygenated blood is required by every cell in the body. Blood pressure will also decrease, which can lead to poor circulation in the extremities and create the possibility of getting lightheaded or fainting when standing suddenly. Furthermore, many long term heroin users exhibit irregular heartbeats due to chronic inflammation, scarring, and fatty tissue buildup in and around the heart. IV heroin use poses the added risks of collapsed veins, abscesses, bacterial infections, and heart infections.
The depressant effects of heroin are most noticeable in the breathing of a user. Immediately after use there will be a severe decrease in the number of breaths someone takes per minute. This is due to a decrease in signals from the brain and is the leading cause of death in heroin overdoses. An overdose victim can die of hypoxic brain damage more readily than heart failure. Furthermore, there are a number of lung issues caused by IV heroin use which may be painful, debilitating, or even fatal. Some of these include pulmonary embolism, pneumonia, and tuberculosis.
Aside from the possibility of nausea and vomiting, the rest of the lower GI tract is affected as well. Heroin produces a semi-paralysis of the large and small intestines which greatly reduces digestion speed and bowel movement frequency. In chronic heroin users, constipation is extremely common with the bowel movements themselves being very difficult to pass. This slowing of function can lead to reduced and slowed nutrient absorption and this can have a direct effect on immune function and overall health. The strain put on the rectum and intestines can also lead to hemorrhoids, prolapse, or hernia. The liver and kidneys also have great strain put on them by heroin use since the liver metabolizes heroin and filters blood from the GI tract, while the kidneys are responsible for blood filtration and waste excretion in urine. Heroin use will only add to their workload and any contaminants or cutting agents may be dangerous or even toxic.
Heroin use has severe effects on reproduction in both men and women, however these effects differ in nature.
- Male Reproduction: In men heroin makes it difficult or impossible to ejaculate while someone is high on the drug. After prolonged use, blood testosterone levels are reduced as well as sperm motility (ability to swim) being impaired and sperm quantity being decreased. These effects on testosterone and sperm are known to persist long after heroin use has been discontinued¹.
- Female Reproduction: In women heroin is known to cause a wide range of menstrual abnormalities as well as amenorrhea, or a lack of menstruation. This may take many months or years to resolve after heroin use has stopped. Additionally, heroin use can severely decrease sex drive in women¹.
- During Pregnancy: Using heroin while pregnant poses a wide range of serious risks for both the fetus and the mother. Risk of maternal death is elevated as well as risk of premature birth or stillbirth, miscarriage, certain birth defects, and neonatal abstinence syndrome¹. Neonates born to mothers who abused heroin often have low birth weight and also show irregular breathing patterns, particularly while sleeping. Additionally, there is a 5-10x increased risk of Sudden Infant Death Syndrome as well as higher mortality in general for infants born to heroin addicted mothers¹.