The Duke of Sussex has said he "slipped into depression for about two weeks" after relocating to Canada in 2019 ahead of his move to the US.

Prince Harry, who recently returned to the UK with his wife Meghan and their two children, said he had originally left the country to "get some space."

The duke also discussed feeling "emotionally numb" after the death of his mother Diana, Princess of Wales, because he felt "disloyal and guilty for the possibility of being happy and joyful without her".

He opened up about his mental health with a neuroscientist in a session for a video learning platform.

He and his brother, the Prince of Wales, have previously been candid about their mental health struggles, including over their mother's death, and both are involved in mental health charities.

Prince Harry, who stepped back from royal duties to move to California with Meghan, made the latest comments as part of a paid-for online masterclass on dealing with grief.

"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," he recalled.

"It was as if I 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 and his wife unexpectedly announced last month that they were returning to the UK with their children Prince Archie, seven, and Princess Lilibet, five, after spending six years in the US. They are now thought to be living in the Cotswolds.

In the video, Prince Harry also revealed that he had a rule that he would never be away from his family for more than 10 days.

He talked about struggling to process his grief in the years after the death of his mother when he was 12.

"In my 20s, I went to war twice thinking I could outrun my feelings," the duke said, referring to his stints in Afghanistan as a member of the Army."But that's not what happened.

"I'd spent so long emotionally numb, to a large extent, because I felt disloyal and guilty for the possibility of being happy and joyful without her.

"I felt like I had to be sad and I had to be emotionally numb in order to prove to her that I missed her."

Prince Harry said in the discussion that after crying at Diana's funeral, he did not cry for nearly two decades, according to news outlets.

He said it was a therapist who suggested he spray her perfume to "unlock everything", adding that this allowed him to discover that "she just wanted me to be happy".

Mary-Frances O'Connor, a neuroscientist and University of Arizona professor who also featured in the online class, explained: "Your brain doesn't register your loved one as gone - it registers them as lost.

"And it will keep searching until you teach it otherwise. We still expect that they're going to walk through the door."

MasterClass approached Harry about appearing in the programme last year and it was filmed in California over the summer, according to People magazine.