Student hangovers are nothing new, but for the first time University of Otago research is revealing how detrimental drinking can be to academic success.
Dr Tamlin Conner, senior lecturer at the university's psychology department, surveyed 281 Otago students via the internet for 21 days.
Students completed daily surveys about how many standard alcoholic drinks they had consumed the day or night prior and the level of their physical, cognitive and emotional function afterwards.
She found a concerning percentage of students drank to excess, but those who consumed only a few alcoholic beverages were able to function at the same rate as those who stayed sober the night prior.
Dr Conner said her research focused on next-day function only, and did not indicate whether regular low-level alcohol consumption would have any long-term effect.
Most of the students surveyed were 19-year-old New Zealanders in their second year of tertiary education.
Participants reported drinking on 26.8% of the survey period days - about two days each week - consuming an average of 7.2 standard drinks.
Males reported drinking 8.1 drinks on 32% of days and women six drinks on 22.5% of days.
Those who consumed alcohol at "low risk" levels during a drinking episode (no more than six drinks for men or four for women) reported levels of next-day physical and cognitive functioning indistinguishable from students who had not drunk at all, Dr Conner said.
"Only heavy drinking (5-9 drinks for women and 7-13 for men) and extreme drinking (10 plus drinks for women and 14 plus for men) predicted significant impairments in next-day physical and cognitive functioning. Extreme drinking produced the most detrimental effects," she said.
Such drinking was associated with the least sleep, feeling the least refreshed, excessive tiredness and a higher incidence of feeling ill.
It was also associated with poor concentration and impaired workload management.
Some males surveyed drank more than 21 standard drinks in a night.
Dr Conner said although aspects of her research were not surprising, she hoped students would be encouraged to consume less alcohol knowing it would directly affect their grades.
"The findings back up the message that the problem is not that people are drinking, it is how they are drinking. Expecting total abstinence from young people is not particularly realistic. However, this research suggests that if they stay within the alcohol guidelines, there should not be too much risk to their immediate health, wellbeing and educational achievements," she said.