The study was carried out by researchers at the University of Southern California on 17,308 human brain scans from the UK Biobank.
According to Lucina Uddin, director of the Cognitive and Behavioural Neuroscience Division at the University of Miami, this is one of the biggest sample sizes ever.
"Back in the day we'd scan 20 or 40 subjects, if we were lucky, for neuroimaging studies. Now we're getting bigger numbers like 200 or 300 individuals. But this is the biggest sample we've ever seen," he said.
Drinking alcohol and smoking daily can affect your brain
Using these many brain scans, the scientists discovered that every gram of alcohol consumed daily caused the brain to age 0.02 years (7 and-a-half days).
For context, a small glass of wine or an average can of beer contains 14 grams of alcohol.
According to the lead author of the study, Arthur Toga, "The 0.4 years of difference was statistically significant. We suggest that daily or almost daily alcohol consumption can be detrimental to the brain."
Reportedly, people who drink alcohol every day had brains that were 0.4 years older than people who did not drink daily.
When it came to smoking, the scientists found that this had a stronger effect on the brain's ageing process.
The study showed that smoking a pack of cigarettes daily for a year is capable of ageing one's brain by 0.03 years (11 days).
Basically, the more you drink and smoke, the more likely you are to have a brain that is older than you actually are.
Commenting on the results of the research, Uddin said, "Looking at brain age is a way of checking how well you've been taking care of your brain. My age is 40, but does my brain look more like a 50-year-old brain or a 60-year-old brain? Do you look younger than your age or older than your age?"
Drinking daily is bad for your brain but the occasional drink is good for the heart
While drinking every day ages your brain, scientists have found that alcohol consumption in moderation has some health benefits.
Dr Qi Sun, a co-author of a Harvard study, told Insider: "There is a really robust link with [alcohol and] high levels of HDL, the 'good' cholesterol. We also see moderate drinking associated with lower rates of chronic inflammation."
Despite the findings of the study, he stressed the need for balance - drinking occasionally and eating a healthy diet.
"It's the all-round package that gives you the most benefits. People shouldn't cherry-pick any individual component or another. If you drink alcohol, it's very important that you drink responsibly, not in excess, and that you also focus on eating a healthy diet, maintaining a healthy body weight, not smoking, and exercising. If you don't drink you don't need to start drinking," he stated.