Understanding Addiction: The Basics

by Jessica Hulsey

In my book Understanding Addiction, I dig into key topics about addiction and answer common questions that family members and caregivers have about substance use disorders (SUD), the medical term for addiction. It isn’t an excerpt from a medical textbook or a scientific journal. Instead, I’ve sat down with physicians and researchers in the addiction field to translate the science into understandable terms that I hope you find helpful.

A Medical Condition

The first thing to note is that substance use disorders are a very common illness in the United States, with millions of families currently struggling. You and your family are not alone. Almost half of Americans report having a family member or close friend with an addiction, and more than 48 million people aged 12 or older—one in six people in the United States—meet the diagnostic criteria for a substance use disorder. In comparison, there are approximately 30 million people in the United States with heart disease, 29 million people with a diabetes diagnosis, and 2 million new cancer cases each year.

Addiction is a medical condition that affects the brain and can change a person’s behavior.  It’s characterized by a loss of control over a person’s substance use, as well as continued use despite consequences—such as loss of a job, arrest, or damaged relationships. It can happen to anyone regardless of race, age, or socioeconomic status. Many people start using substances to feel good or out of curiosity. However, an SUD affects brain function as it develops and progresses, making it harder for a person to control their use. The impairment in self-control is the “hallmark of addiction,” according to the National Institute on Drug Abuse. What was once a decision to use turns into a compulsion. This is why engaging with treatment as soon as possible is so important.

Addiction and the Brain

Because of the impact addiction has had in my own family, I set out to learn about addiction, how it can affect the brain, the psychological and social components, and what treatment entails. I dug into learning and translating what that meant and how it affects those struggling with the illness.

I found a famous scientist in the addiction field, Dr. Nora Volkow, a Mexican-born neuroscientist with curly, untamed blonde hair that has too much energy to lie down. The head of NIDA, the agency at the National Institutes of Health (NIH) that studies addiction, Nora spoke to me unpretentiously and patiently. I had so many questions. As a psychiatrist, she had been intrigued by the behaviors of patients she saw who struggled with addiction. In the 1990s, she started running brain scans of those struggling with addiction, and they showed the effects of substance use disorders. The scans, blobs of yellow, blue, and red. The proof. Like other diseases, from heart disease to Alzheimer’s, the scans showed the physiological effects of addiction. She taught me that there are two main parts of the brain affected by drug use: the limbic system and the cortex. It sounded like Latin to my unscientific ears, but I learned.

Turns out the limbic system—this primal, mammalian part of the brain—is responsible for our basic survival instincts. When we humans do the most basic, fundamental things to stay alive—like eat, drink, find shelter, have sex, or care for our young—our brains reinforce these behaviors through a release of dopamine from this region. Pleasure. Reward. Then we record a memory of that feeling so we seek it again. This is our survival hardwiring. And then there is the pre-frontal cortex, which is what separates us from other animals and controls decision-making and impulse control. When you use drugs or alcohol, the same dopamine process in the survival center activates. And with too much use, that substance can hijack that part of the brain. It changes the brain and weakens this reward-producing survival contraption to make it believe that the primary need for survival is the drug—more important than food, than shelter, than taking care of your baby. And the hijacker is hungry, it needs more and more to reach the same level of reward or feeling of pleasure, so the brain becomes increasingly damaged.

Brain scans show that the damage to the brain that happens during addiction can, in many cases, be reversed. For example, one study found that the length of time abstinent from alcohol is associated with improved executive functioning (thinking/decision-making), larger cerebellar volumes (the size of your brain), and improved memory. There are many factors to consider, including the types of substances and the length of time in active addiction and other health conditions. This is also an emerging area in science, so we’re learning more each year.

Biopsychosocial Components of Addiction

While addiction is categorized as a brain disease, it has other components as well.  You may hear about the biopsychosocial model, which comes from combining the biological, psychological, and social factors that contribute to many chronic illnesses, including addiction. The biopsychosocial model recognizes that there are multiple pathways to addiction, such as genetic predisposition, psychiatric and psychological factors, and unhealthy coping skills. The significance of these specific pathways depends on the individual.

The biopsychosocial approach was one of the first models to recognize the importance of treating the whole person and not just the disease. It was conceptualized in 1977 by psychiatrist Dr. George Engel, who proposed that the treatment of illness should consider psychological and social factors in addition to biological ones. Engel stated, “that to understand and respond adequately to patient’s suffering—and to give them a sense of being understood—clinicians must attend simultaneously to the biological, psychological, and social dimensions of illness.” The goal of a biopsychosocial response is to work together with the patient to discover the different underlying causes and introduce appropriate treatment models to create a unique pathway to recovery.

To learn more, download or listen to Understanding Addiction today.

Citations:

1. Substance Abuse and Mental Health Services Administration. Key substance use and mental health indicators in the United States: Results from the 2022 National Survey on Drug Use and Health (HHS Publication No. PEP23-07-01-006, NSDUH Series H-58). 2023. Center for Behavioral Health Statistics and Quality, Substance Abuse and Mental Health Services Administration. https://www.samhsa.gov/data/report/2022-nsduh-annual-national-report

2. National Institute on Drug Abuse. Drugs, Brains, and Behavior: The Science of Addiction. 2020. https://nida.nih.gov/publications/drugs-brains-behavior-science-addiction/preface

3. Liu RS, Lemieux L, Shorvon SD, Sisodiya SM, Duncan JS. Association between brain size and abstinence from alcohol. Lancet. 2000 Jun 3;355(9219):1969-70. doi: 10.1016/s0140-6736(00)02332-1. PMID: 10859046.

4. Borrell-Carrió F, Suchman AL, Epstein RM. The biopsychosocial model 25 years later: principles, practice, and scientific inquiry. Ann Fam Med. 2004. doi: 10.1370/afm.245. PMID: 15576544; PMCID: PMC1466742.

Excerpts from Understanding Addiction: A Guide for Families by Jessica Hulsey © 2025