(Inside Science) -- Around 5 million people worldwide are expected give up booze for the month of January according to Alcohol Concern, the British charity that popularized the dry January campaign a few years ago. It makes for a popular New Year’s resolution, but whether the act of abstinence for 31 days makes any meaningful difference to your health is far from clear, and experts say it largely depends on what you do come February.
"I sit on the fence -- I can see both sides of the argument," said Ian Hamilton, a registered mental health nurse at the University of York in England whose research focuses on the relationship between mental health and alcohol use. "The idea of recalibrating our relationship with alcohol is no bad thing, but there are risks to this campaign too. Fasting and then returning to bingeing for the rest of the year is an obvious danger."
Drinking alcohol excessively on a regular basis or even just a single time can take a toll on multiple organs, according to the U.S. National Institute on Alcohol Abuse and Alcoholism. It obstructs the brain’s communication pathways, which can cause mood changes and coordination problems. Alcohol can also cause irregular heartbeats, high blood pressure and strokes. It is a major cause of liver disease and can increase the risk of developing a number of different cancers as well.
But scientists say there is not enough data on the long-term health benefits of going dry for a month -- and what data do exist are flawed.
"There is actually very little evidence about the benefits of short-term abstinence. Much of our knowledge comes from when people are forced not to drink, such as during military training, and when they finish there is a rebound effect," said Richard de Visser, a psychologist at the University of Sussex in England. "The other evidence showing this rebound comes from animal studies, but that’s where you’ve trained them to be addicted, and most humans aren’t addicted."
The situation might be very different, de Visser argues, when abstinence is voluntary and done with the supportive feeling that comes with 5 million other people joining you -- so he asked the charity Alcohol Concern for their data to test his thinking.
In 2016, de Visser published a paper in the journal Health Psychology, based on one-month and six-month follow-up questionnaires with 857 of the people who signed up for dry January with Alcohol Concern (249 were male and 608 were female). His results suggest that going sober for a month does have an overall positive impact.
"We found that a small number, 10 percent, exhibited a rebound effect and drank more than they did in the months before dry January. About 40 percent drank the same but the biggest group, of about 50 percent, were drinking less," de Visser said.
These results should be viewed cautiously, Hamilton advised. "Looking at Richard’s article, it seems there is some longer-term effect, but my concern is that he is studying a group who have completed the program and agreed to participate in the study. But I’m far more interested in the people that fail and don’t agree to participate. His sample is self-selecting."
This, said de Visser, is a valid criticism of his work; participants may have been more likely to agree to take part in his study if they believed they have successfully reduced their alcohol intake.
Breaking from booze for a month may confer health benefits, said Gyongyi Szabo, a professor and vice chair of research at the University of Massachusetts Medical School, in Worcester, where she investigates alcohol-related liver diseases at the cellular and molecular levels.
"It really depends on how long someone has been drinking and how much they’ve been drinking," Szabo said. Age and genetics have a lot to do with it too.
"If the drinker is young, say in their 20s, and hasn’t been drinking too much, then one month of sobriety could bring the liver back to normal," she said. "But if you’re in your 30s and have been drinking for 10 years, then it’s not looking so good, and when you’re in your middle ages you’re much less likely to see significant improvement in a month."
Alcohol-induced liver damage continues longer in women compared to men even after cessation of alcohol use. The same amount of alcohol is more likely to cause liver damage in women than men. This is partly due to size -- men are typically larger than women -- but it is also thought that sex hormones could play a role too.
Liver aside, those who successfully complete dry January anecdotally report a number of health benefits, Hamilton said.
"Sleep would hopefully improve and mental health may improve too, although the benefits are more likely to be physical," he said.
Unfortunately, Hamilton said, all these benefits "are short-term and unlikely to be there in six months’ time if you’ve returned to your old behavior."
Both the British and Canadian governments, among other groups, recommend committing to at least two alcohol-free days a week throughout the entire year, while making sure not to overdo it the other five days a week.
Hamilton agrees, "I’d rather see someone do two days a week than someone go dry for a month and yo-yo."