Addiction has always been known to run in the family, a fact now supported by decades of rigorous observational research. For centuries, the trend was chalked up to the consequences of upbringing, class, or race.
In 1967, two researchers selectively bred rats depending on their affinity to morphine addiction. They were able to predict a rat’s proclivity for opioid abuse, given the trait in the parents, regardless of environmental factors. Researchers further discovered that the rats at risk for morphine addiction also had a higher chance of developing alcoholism. These scientists concluded that there was at least one genetic factor contributing to addiction.
The exact mechanisms of this trend are still being explored; the battle of nature versus nurture has been difficult to tease apart.
Whether it’s caffeine or heroin, some similarities underlie all types of addiction.
At the very least, we’re aware that addiction usually involves the ‘reward pathways’ in the brain - a dopamine-fueled system that dictates our motivations. Some compounds - like cocaine - act on this network itself. Many recreational drugs either increase dopamine production or limit its reuptake.
On top of that, how our bodies metabolize drugs and toxins plays a significant role in the way we react to the substance. In the case of alcohol, it is converted into a toxic by-product that is best characterized by the hangover it causes. This metabolite changes into a harmless compound that can be used by the body or disposed of. Therefore, the speed and efficiency of both these steps can significantly affect your relationship with alcohol.
The best example of a genetic effect on drug tolerance is known as the “alcohol flush reaction.” It implicates the second conversion step mentioned above: the build-up of toxic metabolites after drinking. For over 30% of East Asians, this process occurs very slowly, resulting in very uncomfortable side-effects. As a result, they’re significantly less likely to drink at all, effectively eliminating the risk of alcoholism.
This phenomenon is due to deficiencies in the genes related to alcohol metabolism. It is also the only addiction-related variant assessed in 23andMe’s Wellness panel. This has an indirect association with the risk of alcohol abuse. Other genetic mutations have demonstrated a much more pervasive impact.
A shocking example implicates a gene associated with dopamine activity in the brain. An ancient fragment of viral DNA can be found in a certain ‘unused’ part of the RASGRF2 gene, passed down through the generations. Furthermore, this genetic ‘infection’ is associated with a higher risk of intravenous drug use, a hallmark of significant addiction.
This demonstrates the power of dopamine in substance abuse disorders. It also indicates how easily the balance of this neurotransmitter can be disturbed.
Recent estimates suggest that as much as 60% of addiction risk can be blamed on your genetics. Yet, only in the last few years have researchers made significant strides in identifying the exact genes and variants. As shown with alcohol, there can be many different variables that might increase your risk of dependence on any particular drug.
Addiction is a ‘complex trait,’ like your risk for cancer or diabetes. No single ‘addiction gene’ is easily assessed. Like health reports created by 23andMe, estimates are based on many genetic variants, to produce an overall ‘risk score.’ In the same way, lifestyle components are factored into any health and wellness decisions, along with the results of a DNA test.
As of 2019, there are at least ten genetic variations that have been confidently associated with a higher risk of addiction. The majority are involved with dopamine-related pathways and also correlate with measures of impulsivity and compulsivity. In people with all these ‘risk variations,’ there is a very strong association with a clinical diagnosis of alcohol dependence.
This promising line of research is especially important in light of the ongoing opioid epidemic in the United States. People who would have otherwise never come into contact with such powerful drugs are now falling into intense addiction. The crisis has reached a point that doctors are now considering genetic tests for addiction risk before even signing a prescription.
Addiction is most likely to first appear in the late teens and early adulthood. But, it is an affliction that can strike at any time, to anyone. Knowing if you have a genetic predisposition may help direct lifestyle decisions and take appropriate precautions. However, while addiction does run in the family, there are a million factors that might have held it at bay for previous generations.
If you’re curious or concerned, there are some commercial DNA tests available that are as easy as 23andMe or Ancestry - employing a simple cheek-swab. As with any DNA test, there are pros and cons, and negative results can still be harmless, given the right context.
Whether a DNA test indicates that you are at risk - or not - there are some concrete actions you can take to limit your chances of developing an addiction.
The Substance Abuse and Mental Health Services Administration’s National Helpline is a free, confidential, 24/7, 365-day-a-year treatment referral and information service (in English and Spanish) for individuals and families facing mental and/or substance use disorders.