Prince Harry revealed he “slipped into depression” after fleeing the UK with Meghan Markle and their son, Prince Archie, in 2019.

During a new MasterClass session “Redefining Grief: Building Resilience Through Loss,” hosted by neuroscientist and academic professor Dr. Mary-Frances O’Connor, the Duke of Sussex said he experienced an “adrenaline crash” when the family arrived in Canada at the time.

“Being in Canada, away from the stressful environment where presumably my body was just pumped full of adrenaline, within two or three days, I experienced this adrenaline crash, something that I’d never experienced before,” Harry, 42, said.

The “Spare” author explained that he realized he “needed stress in order to get the adrenaline to make my brain function because I became useless around the house.”

“I actually slipped into depression for about two weeks and I felt like I couldn’t function without adrenaline,” he added.

Harry and Markle, 45, began living in Canada with their then-infant son in late 2019. They remained there for several months after announcing they were stepping back from their royal duties in January 2020.

The couple and Archie later relocated to Montecito, California, where their daughter Lilibet was born in June 2021.

In August, the family of four moved back to the UK.

During his MasterClass, Harry reflected on feeling “absolute panic” when he was carrying out his public duties in the UK.

“I started to realize that I had become seriously depleted when just putting a simple dress shirt on — the tightening of the collar — literally felt like I was suffocating, and I would be experiencing panic attacks just in the car on the way to work,” he said.

“And that’s when I realized, okay, there’s something bigger, there’s something else that you need to look into here.”

Harry also said that his “biggest anxiety” when he was a working royal was the “fear of sweating.”

“It was the fear of people seeing me looking disheveled and me not being able to explain to them in one short sentence what’s actually going on,” he explained. “I would feel like I’ve just been in a boxing match.”

Elsewhere during the interview, Harry shared that joining the military at age 20 was the “perfect distraction” from grieving his mom Princess Diana’s tragic death.

“For 15, 20 years, when I was being asked, ‘Are you okay?’ My response was, ‘I’m fine,'” Harry, who was 12 when his mom died, recalled. “It was numbness, emotional shutdown. And without knowing it, adrenaline was pushing me, was driving me.”

Harry admitted his “post-traumatic stress was not tied” to his military tour in Afghanistan, but instead that experience “appeared to be a trigger for other traumas that had stored themselves within me.”

As Page Six previously reported, the Sussexes moved back to England to be closer to Harry’s cancer-stricken father, King Charles III.

But Charles, 77, has made it clear that the couple are living in the UK as “private citizens with commercial and charitable interests,” and not as working royals.

Harry gave an update on life in the UK last month, gushing that “it’s great to be back on British soil” at an Invictus Games charity event in London.

He also confirmed his two children “are in school” and the family is “happy.”