The brain is the most complex organ in the human body. You need your brain performing at peak levels for even the most basic functions such as eating, sleeping, and even walking.
We constantly adapt to our environment when the brain performs well. Consequently, it is the adaptive feature of the brain that also feeds addiction.
Every part of the brain has a job to do. Drugs interfere with its normal processes. Long-term use could change it completely, causing devastating diseases that have lifelong consequences even after you quit.
How does addiction happen in the brain?
Drugs affect three areas of the brain: the limbic system, the brain stem and the cerebral cortex.
The cerebral cortex is the outer part of the brain. Certain areas process information from the senses that allow you to hear, see, taste and feel. The limbic system controls emotional responses, such as pleasure. It recognises the actions that cause pleasure and motivates you to repeat them.
The brain stem controls the bodily functions that keep you alive. This includes digestion, blood circulation and breathing.
The effect of drugs on the brain depends on the substance and the method by which it was consumed. When you inhale, smoke, chew or inject a drug, it is more potent and dangerous than swallowing. The former method circumvents how nerve cells usually send, receive and process information.
The substance overstimulates the brain’s reward centre and encourages you to keep increasing your next dose. Drugs like heroin and marijuana mimic naturally-occurring neurotransmitters in the body. The abnormal messages they send to the brain lead to problems.
Dopamine and addiction
Addiction to a substance or behaviour usually results from a continuous rise in dopamine levels. It is the brain’s reward centre that is responsible for the sensations you feel when you run, have sex, or eat junk food. Consumption of drugs such as cocaine and methamphetamines increase dopamine levels in the brain.
According to Dr Nora Volkow from the National Institute on Drug Abuse, the way the brain becomes addicted to a substance relates to higher dopamine levels stimulated when you take the drug. The resulting pleasure sensation from higher dopamine levels creates a motivation to perform the same action.
Addictive substances flood the limbic system with 5-10x the normal amount the brain produces. Repeated use tricks the brain into believing the behaviour is normal and only the drug will bring pleasure.
It explains why a person with a substance use disorder injects crystal meth, increases dopamine, takes another dose, a third, fourth, until they’ve lost count. There is no stopping after a while. Each dose is larger than the last to feel the same pleasurable rush.
Over time, high levels of dopamine change how your brain produces and processes the naturally-occurring chemical. It leads to physical dependence, cravings, continued use, despite knowing the consequences.
Addiction physically changes your brain
Researchers are getting closer to understanding more fully how addiction affects the physical structure of the brain. One way the body responds to addiction is to weaken and shrink the Anterior Cingulate Cortex.
This is the part of the brain that links conflict-pain with behaviour-thoughts. When substance abuse influences the ACC, it’s harder to deal with conflict in a healthy way.
Changes are more significant in the developing minds of young people. It causes slow development and interferes with the part of the brain that makes rational decisions.
While changes to neurons might not be permanent, research has shown it could last years. The long-lasting effects make it extremely difficult for long-term addicts to stay abstinent. The cravings they experience are more intense, leading to relapse in most cases.
Individuals who were long-term alcoholics had smaller areas of white matter. Effects such as the death of neurons could be permanent in some individuals. Researchers found that restoration happens more quickly for women than men.
The ACC shrinks and weakens in people who were long-term addicts. It swells back up when they recover. This is proof that it doesn’t cause addiction, rather responds to it.
Why are drugs and alcohol more addictive than natural rewards?
The brain releases more dopamine than normal when you abuse drugs or alcohol. Continuous use means the brain grows heavily reliant on higher levels of dopamine to perform basic functions. The higher the quantity, the more you will require in the next dose to feel the original effect.
The brain reaches a tolerance level where it has adapted to high levels of dopamine. It is difficult for a non-addict to understand. Think of it as the difference between someone using a loudspeaker to say something to you and another person whispering in your ears.
While you turn down the volume because it’s too loud, the brain of an individual with drug use disorder adjusts by limiting the number of receptors receiving signals or producing fewer neurotransmitters in the reward centre.
This, in turn, reduces the addict’s ability to feel any sort of pleasure from normal activities such as eating, sleeping or having sex, increasing the desire for more drugs. When they feel depressed, lifeless and without motivation, they take a higher dose to experience the normal levels of reward.
From liking to wanting, recreation to essential
No addict took drugs or alcohol with the intention of becoming an addict. Yet, millions are caught in its throes. Over two-thirds of individuals with substance use disorder also abuse alcohol. Major drugs causing addiction are marijuana, cocaine and prescription pills. Studies have revealed that 40-60% of an individual’s chances of becoming an addict is hereditary.
All drugs of abuse, including heroin and legal highs, cause a powerful surge of dopamine in the nucleus accumbens. The intensity of the release, method of administration and speed of dopamine release could lead to addiction.
Addiction cannot be treated by will alone. The success of treatment is dependent on the individual’s desire to stay abstinent, get follow-up care and follow a relapse prevention plan. Addiction manifests in cravings, loss of control and continued use. While physical symptoms may reduce after an addict gets help, emotional and psychological triggers could lead to a relapse after many years have passed.