What Are The Causes Of Substance Use Disorder
In our most recent article we discussed why alcoholics and other drug addicts continue to drink and use despite increasingly difficult social, legal, professional and health related problems. That begged the question of how it is that one person will start using alcohol or cannabis, or use an opioid prescription as prescribed, and use these drugs safely, but another will start down the trail of abuse, dependence and addiction.
In discussing causes, Johns Hopkins medical center reviews separately the cultural acceptance of alcohol and drug use on the one hand and causes of substance use disorder on the other. They note that there are cultural and social factors that influence what is considered acceptable drug or alcohol use. Public laws determine what kind of drug use is legal or illegal. A case in point is the growing, societal acceptance of cannabis use and the changing legal landscape (we have written previously about how this is not as clear an issue favoring legalization as some would have us believe).
Substance use disorder, on the other hand, is a medically defined disease caused by multiple factors including genetic vulnerability, environmental stress, social pressures, individual personality characteristics, and other behavioral health issues. Substance use disorder expresses itself differently for individuals and determining which of these factors has the most influence in any one instance cannot certainly be determined as of yet.
Discussing these two perspectives separately helps us distinguish between occasional, socially unacceptable behavior and pathologic substance abuse and addiction. We all know someone who made a mistake with alcohol and vehicular use, learned their lesson, perhaps painfully, and never made that mistake again. We all know someone who acted poorly at a family event one time, regretted that behavior and apologized. These are instances of socially unacceptable use of a socially acceptable drug but not, necessarily, addiction. A repeated pattern of use and abuse despite mounting personal, legal, employment and family problems is a pattern of abuse that indicates the development of substance use disorder.
A review on the Mayo Clinic website discusses causes, risks, complications for developing a substance use disorder. They note factors that can affect the likelihood and speed of developing an addiction:
Genetic predisposition. There is ample evidence that there are gene expressions that impact processing alcohol and other drugs and result in differences in brain chemistry and that these genetic variations can be inherited. Drug addiction is more common in some families and likely involves an increased risk based on genetic make-up. People who have a blood relative, such as a parent or sibling, with alcohol or drug addiction are at greater risk of developing a drug addiction
Mental health disorder. Individuals with a mental health disorder such as depression, attention-deficit/hyperactivity disorder or post-traumatic stress disorder are more likely to become addicted to drugs. Self-medicating can seem an effective strategy but will usually exacerbate these problems
Lack of family involvement. Difficult family situations or lack of a bond with parents or siblings may increase the risk of addiction, as can a lack of parental supervision
Early use. Using drugs at an early age can cause changes in the developing brain and increase the likelihood of progressing to drug addiction. It appears that interactions in the yet developing brain may lead to addiction and dependence while first use after further development will not. Hence prohibitions against underaged use are reinforced
Using highly addictive substances. Some drugs, such as stimulants, cocaine or opioid painkillers, may result in faster development of addiction than other drugs. Smoking or injecting drugs can increase the potential for addiction.
Recovery.org provides an excellent overview in a 2025 article about causes, symptoms, interventions and treatment. They note that despite advances in research it is still not perfectly clear what specifically causes addiction as risk factors vary between each individual, and no single factor will cause or prevent addiction. It is clear that if a person has multiple risk factors the likelihood of misusing substances or developing an addiction increases.
Recovery.org lists certain of the factors already discussed but with different emphases. These include:
Aggressive behavior in childhood
Neglect from parents or guardians
Early experimenting with drugs or other substances
Access to drugs at school
Poverty in the community.
They also have a slightly different discussion of genetic influences. Their report suggests that addiction is moderately to highly heritable. The relationship with first-degree relatives who struggle with addiction strongly influences the risk of developing an addiction themselves. Recovery.org reports that there are over 400 locations in the human genome that may influence activities like smoking or alcohol use.
This article also emphasizes home influences on later substance use, abuse and addiction. Specifically they discuss that children of parents who use drugs and alcohol and/or are involved in criminal activity are at risk of misusing substances. Parents may introduce children to drugs, model negative behaviors, and create environments that increase stress. Similarly, exposure to drugs and alcohol in schools or neighborhoods especially at an early age can enhance risk of developing an addiction.
We cannot overemphasize the impact of early childhood experiences on an individual’s physical and emotional health. Adverse childhood experiences especially can be stressful, traumatic events that may lead to physical and emotional difficulties and are a significant contributor to the development of substance use disorder. Adverse childhood events that may also occur in adolescence and beyond include:
Verbal abuse
Physical or emotional neglect
Witnessing violence
Having a family member with a mental illness
Having an incarcerated family member
Having a family member who is addicted to drugs or alcohol
Parental separation or divorce
Sexual abuse
Violence
Finally, the link between substance use disorder and other behavioral health conditions is very strong. A person is said to have a co-occurring condition when more than one disorder or illness presents in the same person, for example, the presence of depression and a substance use disorder. It is estimated that in the United States, 7.7 million people have co-occurring mental health and substance use disorders. It is difficult to determine if or how one leads to the other or which came first, but there does appear to be a relationship between co-occurring disorders. Neuroscientists believe that neurotransmitters in the brain, such as dopamine, are impacted by substance use, but they also play a role in various other mental health conditions. Brain changes resulting from mental health disorders may impact or lead to substance use and vice versa.
The medical science of addiction is progressing rapidly. As we have to date treated substance use disorder as a behavioral health condition we have treated it through traditional behavioral health therapies that have only recently turned to neuroscience. Perhaps we will arrive at a point of recognizing a basis in brain chemistry more certainly and better define the seemingly obvious genetic predispositions, and that will lead to other approaches and solutions to abuse. That does not suggest that the co-attendant psychosocial issues will, necessarily, be treated in similar fashion of course.
Until that time the causes of an individual developing abuse and addiction will not be as specifically clear. We know that we live in a culture that promotes alcohol use, increasingly cannabis use, and that use is widespread. We have previously noted that 70% of American adults use alcohol, 93% of Americans believe that cannabis use is acceptable in certain instances and 50% of American adults have tried cannabis at some point in their lives. It is no surprise that American youth and early adults would experiment with using alcohol and cannabis.
At the point of initial use some individuals with a genetic predisposition may start down the trail of abuse and addiction. Individuals with a first degree relative appear to be more at risk. As of this writing there is no “test” as we might have for other diseases such as diabetes.
We also know that there are environmental factors. These include growing up in those parts of society where alcohol and drug use are not only condoned but are part of broad use and even expectation. Widespread use in the home, in recreational settings, and in schools tend to promote early use. We know that early use will more likely result in developing a substance use disorder perhaps due to the still developing brain structure in adolescents.
Adverse family situations are also likely to produce patterns of substance abuse. Addicted parents, extensive use of drugs in the home, parental incarceration, parental criminal behavior are all likely to encourage abuse and possibly accelerate addiction. Physical, sexual, mental abuse and parental neglect are also major contributors to starting alcohol and drug use and to developing patterns of abuse.
There is a clear link between substance use disorder and other behavioral health conditions. We do not yet know if these comorbidities are expressions of the same underlying condition or that they create predispositions and if so is one a stronger influence on the other. We do know that some individual with a behavioral health condition attempt to self-medicate and that it rarely turns out well.
Finally, this discussion has tended to consideration of alcohol and cannabis. The same factors apply to other schedule 1 and schedule 2 narcotics. The difference is that there is ample evidence that these drugs create a much stronger physical linkage and are much more likely to result in addiction. The largest killer of Americans, nicotine, would be included on this list.
Today we do not have a specific understanding of the causes of substance use disorder that we can apply to every individual and diagnose the disease. We do know that there are genetic predispositions that seem to lead one individual to abuse and addiction while another will use alcohol and cannabis and prescription pharmaceuticals safely. We are also well informed about environmental influences and the relationship with other mental health conditions. All of these environmental factors also provide information about protective measures that may be taken especially where there is a close relative who we know suffers from substance use disorder.
Gene Gilchrist
September 2025
