(Reuters Health) - About a third of 15-year-olds in the UK have blacked out due to alcohol, a new survey indicates - and the rate rises to nearly three-quarters by the time they reach 19, researchers found.

"Blackout is associated with pretty severe intoxication," said Dr. Marc Schuckit, the study's lead author from the University of California, San Diego. It occurs when the blood alcohol level "is about double what is legally drunk."

"We found that (blackouts) were shockingly common" among the teens in the survey, Schuckit told Reuters Health.

Although there are some variations among U.S. states, most set a blood alcohol content of 0.08 percent as the legal limit. The National Transportation Safety Boardrecommended lowering that level to 0.05 percent, which is the cutoff in many European countries.

Schuckit believes teens, and popular culture, view blacking out as funny. But it's very serious, he said, adding that when blood alcohol levels are high enough to cause blackouts, "people are very likely to get into trouble."

The 1,402 teens in the study, all of whom reported drinking when surveyed at age 15, were surveyed again at ages 16, 18 and 19.

At age 15, 30 percent reported drinking to the point where they could not remember what happened the next day. By age 19, about 74 percent had experienced an alcohol-related blackout.

There were four distinct drinking patterns, researchers found. About 5 percent of participants did not report any blackouts. In about 30 percent, blackouts increased rapidly as kids got older. In about 45 percent, blackouts slowly increased with age. And in about 20 percent, there was a steady rate of blackouts throughout the study.

"What is really important is the 'never had a blackout' group was relatively uncommon, compared to the other groups," Schuckit said.

Some students were more likely to report alcohol-related blackouts, compared to other students.

"The first was a surprise to me," Schuckit said. "That is if you're female."

His group also reports in the journal Alcoholism: Clinical and Experimental Research that drinking more, smoking, having fewer inhibitions and having more friends thought to be drinking and using drugs were all tied to an increased number of blackouts.

While Schuckit said these numbers may be less dramatic among U.S. teens, "there's no way I'm ever going to see a kid from (age) 14 on without asking about their drinking pattern."

If doctors do suspect a teen is on a dangerous path with drinking, he said "what you do is as a clinician is a brief intervention."

A brief intervention is a quick session to make a person think about their drinking and giving them resources to drink more responsibly.

Parents, Schuckit said, should start a discussion about drinking.

SOURCE: Alcoholism: Clinical and Experimental Research, online December 16, 2014.