Dr Garret McGovern was responding to the results of a UK study that showed 33% of young people have used illegal drugs in the past year.
This is a 10% jump on the previous year.
"It mightn’t surprise you but I think alcohol use kind of went through the roof during lockdown and there was a recoil effect when restrictions are lifted,” Dr Garrett McGovern told Newstalk.
He said the findings are alarming, but just confirm what he is seeing in his work.
“I think people are underestimating the impact that lockdown has had on people,” the Medical Director at the Priory Medical Clinic said.
"It’s had devastating effects on some people and certainly some people I’ve treated just couldn’t deal with it at all.”
"They went into themselves, they got depressed and they either drank more or they used more drugs – usually cocaine.”
He said it’s not just young people who are using drugs more than usual.
"People didn’t reduce the drinking that they had developed.”
"Post-COVID, we’re definitely seeing more people presenting for treatment,” he said.
"Initially, when COVID broke we all went quiet in the clinics. We were kind of wondering, ‘What is going on here?’”
"But what was actually festering away at home was that people were using drugs and drinking alcohol and then the whole thing kind of exploded and then it got really, really busy.”
In June, Dr McGovern told Newstalk that there has been a huge increase in the number of people coming forward for cocaine dependence.
"The amount of presentations over the last couple of years - and understandably so, cause people were holed up in the house - men going out to garden sheds away from their wife and kind of snorting away for the evening."
He described the situation as “very, very grim.”
A report from the Health Research Board (HRB) recently showed that Ireland now has the second-highest proportion of 15- to 24-year-olds in Europe who have used cocaine or ecstasy at least once.
It revealed the amount of young people treated for cocaine use between 2011 and 2019 increased by more than 170%.