For most women, drinking up to four standard drinks in a night can cause their mood and wellbeing to be lower the next day, and for men, drinking up to five standard drinks.
But University of Otago researchers studying more than 1300 young adults, with an average age of 19, have been surprised to find their moods were not affected by those levels of consumption.
It took higher levels of consumption to bring about "hangxiety".
Lead author Jenna Gawn, who conducted the research as part of her honours degree in psychology, studied the relationship between a subject’s alcohol use and their mood and wellbeing the next day.
The participants completed two daily diary studies over the course of one or two weeks, in which they reported how much they drank the previous night and how they felt the following day.
Alcohol consumption was split into three categories — low-risk (one to four drinks for women, one to five for men); medium-risk (five to nine drinks for women, six to 11 for men); and high-risk (10-plus drinks for women, 12-plus for men).
She said people who drank medium- and high-risk amounts reported having a significantly lower mood, vigour and wellbeing the next day, compared with a night of no drinking.
"They were also more confused and fatigued."
However, those who drank in the low-risk category were indistinguishable from nights of no-drinking.
"Interestingly, drinking within these guidelines did not impair mood and wellbeing," she said.
Co-author and University of Otago psychology Prof Tamlin Conner was also surprised by the findings.
"We expected that low-risk drinking might impair next-day mood, but found no evidence of that.
"We were also surprised there was no evidence of ‘hangxiety’ — feeling anxious or worried after a night of drinking."
Prof Conner believed four drinks was "quite a lot".
"From a public health perspective, knowing how alcohol is metabolised, four drinks seems like a lot.
"What it equates to in a young adult limit is half a bottle of wine over the course of a night.
"What we don’t know is the time frame that they were taking to drink these drinks. It might have been over a longer time frame.
in the public health guidelines for avoiding binge drinking, their mood and wellbeing seemed to not be impaired."
However, she had a caveat.
"This is not to say that that won’t cause acute or long-term health effects.
"Our work is not saying that this is recommended.
"The long-term effects of drinking that much would certainly manifest metabolically, cognitively and so on."
As tertiary institution orientation weeks were coming up, Ms Gawn hoped the research would help young people make more informed decisions when drinking.
"It’s not just about having fun tonight, it’s also about feeling good tomorrow."
