I’ve long suspected that the single most important question when it comes to understanding addictions is— who gets it, and why?

In other words, given the reality that so many people drink and use mood and mind-altering drugs, why do only some – usually a minority, but a substantial one– go on to qualify for what we currently term a Substance Use Disorder (SUD)?

I’ve long thought the answer would have to involve genetics. Not only genetics, however. Other factors can and do play a role.

Mark S. Gold MD, an eminent figure in the scientific study of addictions, reviews the current state of knowledge in Psychology Today. Here’s the link:

Genetics and Addiction: What We’ve Learned

Take Alcohol Use Disorders (AUD), for instance. Gold notes that the heritability of alcohol dependence is up to 60%. If I recall correctly, that’s well above some other psychiatric disorders. Comparable to bipolar disorder.

I wasn’t surprised to learn that “twenty-two percent of adults in the United States have at least one biological parent with alcohol use disorder (AUD).” The 2020 Census put the US population 18 years or older at around 260 million people. That translates to 57 million Americans at increased risk for an AUD during their lifetime. That’s based on having one biological parent.

With two biological parents, the ofworing’s risk is 4.4 times higher than average.

We’re talking odds, remember, not certainty. Being at risk does not mean that at some point, all those folks will wind up in need of addiction treatment. The vast majority will not. Nonetheless, at the level of an individual, it’s something to pay attention to.

What about for cannabis disorders? “Experts estimate that among people who use cannabis, up to 30% may have marijuana use disorder…“ I recall when the estimates were around 9-10%. Has something changed? That number definitely trends in an unfavorable direction.

I assume (hopefully) a large majority of Cannabis Use Disorder (CUD) cases that emerge will qualify as relatively mild. Those with more severe symptoms will continue to predominate in treatment populations, as the result of self-selection.

Still, it does seem that our society is bent on making new cases of CUD at an unprecedented rate. This has to be due to so many more Americans being regular cannabis users. And it’s no longer primarily young adults. Seniors, for Pete’s sake, are now among the fastest growing segments.

According to Dr. Gold, approximately “…50%-70% of an individual’s risk for cannabis use disorder is due to genetic factors.” There’s still plenty of room for environmental influences. For instance, ready access to affordable cannabis products with unusually high THC content… oops.

Inevitably, there will be consequences. Gold observes that new evidence suggests that “…cannabis use disorder and even cannabis use significantly increases the risk for other substance use disorders.” That may explain why so many patients in treatment for alcohol, opioid, and stimulant disorders have long histories of cannabis use, beginning in the early teens.

We’ve come a long way in terms of understanding and appreciating the role of genetics in substance use and related disorders. I’m old enough to recall when simply bringing up the subject of genetics in a conference was enough to draw catcalls from some in an audience of psychiatrists (I’m speaking from experience there).

Fortunately, times do change.