Written by: Shreya Sharma
The Opioid Crisis has been an ongoing health issue amongst North Americans. Learn about the phases of addiction, the effects of Opioid on the brain, and what genetic factors increase your chances of addiction.
Throughout the last century, drug use and abuse has been a critical point of interest for scientists. However, genuine science was often overshadowed by fears, giving rise to misconceptions. In the 1930s, it was believed that individuals with addictions have moral flaws and reduced willpower. By perpetuating these ideas, the response to addiction was punishment instead of treatment and prevention. While perspective on addiction may have changed, drug abuse is on the rise, creating epidemics such as the well-known Opioid Crisis.
Opioids are natural or synthetic substances that bind to specialized receptors in the nervous system. Heroin, fentanyl, oxycodone, and morphine are examples of opioids that share the common effects of pain relief and sedation. Recognizing the physical response to the substance was especially crucial in shedding the belief that willpower was enough to overcome an addiction. Substance dependency is now known as the physiological and biochemical changes that arise from prolonged use (National Institute on, 2019). Chronologically, drug addiction can be broken down into three main phases. The first is tolerance, which occurs when the individual’s response to a drug is not the same as when they first used it, causing them to increase their dose. The second phase, dependence, is marked by the feeling of withdrawal. If the absence of the drug causes significant mental and physical discomfort, the individual can be categorized as dependent on that particular drug. Lastly, addiction is the complete form of the disease. Despite negative consequences from repetitive exposure, the individual can not stop using the substance. Each of these phases have widely different effects on the brain and the body, but they are all linked to the development of long-term issues (National Institutes of Health, 2017).
As an opioid travels through the bloodstream and to the brain, it attaches to mu receptors on the opioid sensitive neurons. This activates the mesolimbic, or dopaminergic, reward system which triggers a powerful release of dopamine. Dopamine then travels to the nucleus accumbens and results in pleasurable feelings.
Dopamine is an excitatory neurotransmitter, often referred to as a chemical messenger between neurons. The association between an activity and its subsequent reward is enough to increase dopamine levels, which is thought to have contributed to the innate human quality of planning and “seeking” behaviours. This characteristic is a significant contributor to addiction development, as an individual is inclined to repeat the activity that brought about pleasurable feelings (Mysels & Sullivan, 2010). The brain creates new memories of the specific environment or circumstances associated with the feeling, which is known as a conditioned association. Excess neural exposure to an opioid increases the receptors and enzymes, inhibits the drug’s effect and results in withdrawal. Eventually, the conditioned associations between the drug and the positive feelings result in cravings and, ultimately, addiction (National Institutes of Health, 2017).
Increased likelihood of developing a disease is often linked to an individual’s genetic background, and drug addiction is not exempt from this. DNA variations known as single-nucleotide polymorphisms are indicators of increased disease susceptibility.
In a study and analysis of male heroin addicts, single-nucleotide polymorphisms in the OPRM1 gene were seen in the subjects with higher levels of opioid dependence vulnerability. This gene is responsible for coding for the mu-opioid receptor (Kosten & George, 2002).
Furthermore, scientific evidence shows that neurons are damaged by continual opioid usage. The most noticeable changes are those in cell physiology, as well as transcriptional processes.
Modified histone methylation heightens the cells’ responses to opioid exposure, and alters the brain processes associated with rewarding behaviours. Additionally, lowered transcription of synaptic activity and neuroplasticity genes causes abnormalities related to addictive behaviours (Harvard Medical School, 2011).
Today, views on substance abuse and addiction have changed drastically, creating an environment that is more inclined to rehabilitate than degrade those who require help. Continuous discoveries about biochemistry and the human body continue to revolutionize our knowledge, allowing doctors and researchers to respond to the issue in the most effective manner possible.
References
Harvard Medical School Health Publishing. (2011, July). How addiction hijacks the brain.
Retrieved August 7, 2020,
from https://www.health.harvard.edu/newsletter_article/how-addiction-hijacks-
the-brain.
National Institute on Drug Abuse: Opioids. (2019, July). Retrieved August 7, 2020,
from https://www.drugabuse.gov/drugs-abuse/opioids#summary-of-the-issue.
Kosten, T. R., & George, T. P. (2002, July). The neurobiology of opioid dependence:
Implications for treatment. Retrieved August 7, 2020, from
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2851054/.
Mysels, D. J., & Sullivan, M. A. (2010). The relationship between opioid and sugar
intake: review of evidence and clinical applications. Retrieved August 7, 2020,
from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3109725/.
National Institutes of Health Library of Medicine. (2017, July 13). Trends in Opioid Use,
Harms, and Treatment. Retrieved August 7, 2020, from
https://www.ncbi.nlm.nih.gov/books/NBK458661/.