6.3 Biological theory

Some researchers believe that substance use disorders are a biological phenomenon; “efforts to target addictions require consideration of how the improved biological understanding of addictions may lead to improved prevention, treatment and policy initiatives”.^[1]  The biological theory of substance use helps us understand how substances impact our brain and the changes that happen.  Please watch the following short video on how substances impact the brain.^[2]

If you think about any activity you participate in, if it makes you feel good, chances are that when you participate your brain is releasing dopamine.  If you remember in Chapter 4, we learned dopamine is a neurotransmitter that impacts the reward centre of the brain.   Your brain typically releases dopamine when you participate in behaviours or activities that make you feel good.  This is released each time you repeat a behaviour.

When you take a substance, especially opiates, your brain releases dopamine.  Every time you take that substance, your brain, and the dopamine it produces are remembering that “feel good” feeling and reinforcing it.  For a person living with a substance use disorder, every time they use a substance it triggers adaptations in dopamine production.  Using a biological theory to explore how substances impact the brain can help with the development of treatment that focuses specifically on the brain.  For example, Methadone Maintenance Treatment (MMT) is a treatment that focuses on the biology of an opiate use disorder and benzodiazepines have been used to target the biology of alcohol withdrawal symptoms.^[3]

We can use biological theory to help us understand the vulnerabilities of some to a substance use disorder.  What is a vulnerable individual?  A vulnerable individual may be someone who has a unique physiology (mental health disorder, brain disorder, or physical disorder).  Certain groups, particularly adolescents and young adults, may be vulnerable to developing a substance use disorder at certain ages, due to the stages of brain development.  Specific brain regions, like the amygdala typically mature slower, impacting decision making, which may be a reason why some youth struggle with substance use.^[4]

Mental health also plays a role in substance use.  Studies suggest some youth who have schizophrenia, and have not been diagnosed, use substances to manage their illness.^[5]  Vulnerable individuals may also be people who have a genetic predisposition (a parent or a close family member who has struggled with a substance use disorder).  For example, numerous family studies, adoption studies, and twin studies suggest genetics plays a role.^[6]  Many of these studies however do not allow us to separate the effects of genetic and environmental influences.^[7]  This means that substance use disorders from a genetic perspective should not be considered simply a biological phenomenon.

Despite significant advances in our understanding of the biological bases of substance use disorders; we know substance use disorders continue to represent a huge public health crisis,^[8] and further research in this area must continue as we support individuals living with a substance use disorder.  Every brain, and every person is different; we must look at biology as one potential factor in a substance use disorder.