An estimated 10 percent of Americans have had a drug use disorder at some time in their lives, but many have gone untreated, according to a new study by the National Institute on Alcohol Abuse and Alcoholism (NIAAA).

Only about one-quarter of people who have ever had a drug use disorder received treatment, the study found.

“Based on these findings, more than 23 million adults in the United States have struggled with problematic drug use,” George F. Koob, PhD, NIAAA Director, said in a news release. “Given these numbers, and other recent findings about the prevalence and under-treatment of alcohol use disorder in the U.S., it is vitally important that we continue our efforts to understand the underlying causes of drug and alcohol addiction, their relationship to other psychiatric conditions and the most effective forms of treatment.”

The study relied on interviews with more than 36,000 adults between 2012 and 2013, Time reports. In JAMA Psychiatry, the researchers note almost 4 percent of those studied received a diagnosis of a drug use disorder in the past year. Men, young unmarried adults, people with lower education and income levels, and white and Native Americans were most likely to have a drug use disorder.

People were more likely to report problems with drug use if they also abused alcohol and nicotine, or had mental health issues such as major depressive disorder, bipolar disorder or post-traumatic stress.

“The prevalence and complexity of drug use disorders revealed in this study, coupled with the lack of treatment, speak to the urgent need for health care professionals to be trained in proper techniques to identify, assess, diagnose, and treat substance use disorders among patients in their practice,” said Nora D. Volkow, MD, Director of the National Institute on Drug Abuse, which contributed funding to the study.