Why does this happen? For some people especially those without any addictive tendencies, it seems like alcohol and drug abuse is a choice. After all, you enjoy a drink every day or may smoke something every weekend. You don’t crave it. You don’t need it to survive. You’re still holding down a job.

All of these beliefs miss some of the most important key components of drug addiction. First, it is never voluntary. Second, there’s a true science behind what happens and why some people suffer from addiction and others do not. A study out of the University of California San Francisco why some people become alcoholics found that moderate drinking causes an increase in a substance that causes the physical change of the brain. This is a slow process, enhanced by binge drinking or drug use. In short, a person’s genetics determine when this substance impacts the brain, how it does, and what the long-term impact of excessive drinking is.

Genetics play a big role in why some people can tolerate substances and others cannot. But most importantly, consistent and even just moderate alcohol or drug intake will impact the chemistry and makeup of the brain, encouraging long term damage to occur.