Students in the thick of midterms may want to take note of a recent study that empirically demonstrates what they may already know: Alcohol consumption before and during final exam period is detrimental to students’ performance. The effect is particularly significant for the highest-performing students, according to the study, which was released by the National Bureau of Economic Research in September.

Prior studies on the effects of alcohol consumption have focused on issues like death and teen pregnancy, which only impact specific individuals. The researchers — economists Scott Carrell of the University of California, Davis; Mark Hoekstra of the University of Pittsburgh; and James West of the U.S. Air Force Academy — decided to focus on college students to study how drinking impacts a broader segment of the population.

The study compared the grades of students who turned 21 just before final exams and just afterward. It used data on 3,884 students at the U.S. Air Force Academy from 2000 to 2006.

The researchers found that students who turned 21 before final exams scored an average of one-tenth of a standard deviation lower than those whose birthdays were after exams. No dip was found among students who turned 20 before exams, showing that there was more than a “birthday effect” at work.

“The performance drop is of approximately the same magnitude as being assigned to a professor whose quality is one standard deviation below average,” the researchers noted.

Researchers used data from the Air Force Academy because it has a strictly enforced ban on underage drinking, as violators of the ban can be expelled. A survey conducted in 2004 found that fewer than 40 percent of students under 21 reported that they had consumed any alcohol since matriculating at the Air Force Academy, while nearly 90 percent of students age 21 or older had done so.

Conversely, a survey conducted by the National Institute on Alcohol Abuse and Alcoholism this year found that 83 percent of college students in America drink alcohol and 41 percent reported having recently had five or more drinks in one sitting.

Another advantage of using data from the Air Force Academy was that all students have a similar course load. Cadets must take 30 core courses and have no choice in professor, and tests are standardized across sections.

The fact that the drop in performance was largest for the highest-performing students, the researchers wrote, “suggests that the negative consequences of alcohol consumption are not limited to a small fraction of users or even to those who might naturally struggle with academics.”