College students today celebrate 21st birthdays with an average of 12 drinks for men and nine for women, according to the most in-depth picture yet of the consequences of heavy drinking.

The University of Texas-Austin research found 78 percent of students cited ill effects, including hangovers (54 percent). Of the 44 percent who had blackouts, 22 percent found out later that they had sex; 22 percent got in a fight or argument. And 39 percent didn't know how they got home.

Although the study focused on just one campus, researchers say this level of extreme drinking goes way beyond "bingeing" — four or five drinks in one sitting. And it's a phenomenon likely being repeated at schools across the country, researchers say. Studying 21st birthday celebrations is a new area of research and no national studies have been done, but studies on a handful of other campuses have found similar extremes.

Of more than 2,200 students in the four-year drinking study that began in 2004, Texas researchers randomly selected 152 students for an analysis focused on 21st birthday drinking, including interviews. All but two of the students said they drank to celebrate.

Consumption varies by region; a recent review by Harvard researchers found more binge drinking at campuses with a strong drinking culture and easy access to alcohol. In Austin, 12 of the 152 students reported 21 or more birthday drinks.

At the University of Missouri, a study of 2,518 students published in June found 34 percent of men and 24 percent of women had 21 or more drinks.

Psychology professor Kenneth Sher, co-author of the Missouri study, said the Texas research is novel. "It's a drink-by-drink reconstruction of the evening," with bartender input on contents and size of each drink.

Texas' larger study of 2,200 students also looked at drinking in the two weeks before and after the 21st birthday and found frequency of drinking increases after 21, but quantity decreases.

Psychology professor Kim Fromme, who directs the Texas study, said turning 21 decreases the risk associated with heavy episodic drinking. Overall, the research found most students drank twice a week or less; 19-year-olds drank the most.

Of the 2,200 students studied, 40 percent of those who were 21 reported driving after drinking in the past three months.