LOS ANGELES, July 17 (Xinhua) -- About 40 percent of adults in the United States who drink alcohol do so in amounts that risk health consequences, a new study has found.

The study, published this week in the Journal of Substance Use, found that 73 percent of those drinking risky amounts were still doing so two to four years later, while 15 percent of those did not drink risky amounts.

"Some people just stop drinking too much, but most continue for years, and others not drinking too much will begin doing so during adulthood," lead author Richard Saitz, professor of community health sciences at Boston University School of Public Health (BUSPH), was quoted as saying in a news release.

"Public health and clinical messages need repeating, particularly in young adulthood. Once is not enough," said Saitz.

The researchers used data collected by interview from a nationally representative sample of more than 34,000 adults in the U.S. who completed the National Epidemiologic Survey on Alcohol and Related Conditions in 2001-2002 and again in 2004-2005.

The survey assessed participants' drinking in the past month using a well-validated interview tool.

"At-risk use" was defined as more than 14 drinks per week on average or more than four on an occasion for men, and more than seven per week or more than three on an occasion for women.

Starting to drink too much was associated with being younger, transitioning to legal drinking age, being male and white, and smoking and drug use, among other social factors, the research found.

Among all the predictors, the biggest one of transitioning to at-risk alcohol use was younger age, particularly among participants who were under the drinking age at the time of the first survey.

According to the 2015 U.S. National Survey on Drug Use and Health (NSDUH), 86.4 percent of people aged 18 or older reported that they drank alcohol at some point in their lifetime, 70.1 percent reported that they drank in the past year, and 56.0 percent reported they drank in the past month.

From 2002 to 2013, the number of American adults who consumed alcohol increased, from about 65 percent to 73 percent. The more concerning finding was that the number of drinkers who displayed hazardous drinking increased 30 percent over this period, according to a previous work published by Bridget Grant, Ph.D. and colleagues last year in JAMA Psychiatry.

According to the JAMA Study, the number of U.S. alcoholics increased almost 50 percent during this 10-year period.