A doctor told Prince Harry that he believes the Duke has Attention Deficit Disorder during a live Q&A.
The claim came during a video event to promote his memoir, Spare.
Dr Gabor Maté, an expert in trauma and childhood development, told the Prince: "Whether you like it or not, I diagnosed you with ADD. It takes one to know one, so I share that diagnosis."
Harry responded: "Okay. Should I accept that or should I look into it?"
Attention Deficit Disorder, more commonly called ADHD, is a neurological disorder that typically causes difficulty focusing and impulsive or erratic behaviour. The condition affects roughly one in 50 adults in the UK.
Dr Mate told the Duke: "Reading the book, I diagnose you with ADD.
"I don't see it as a disease, I see it as a normal response to abnormal stress.
"When a kid is in a stressful environment, one way they cope with it is they scatter their attention so that they remove themselves from the stress.
"I think there's a lot of stress in your life. And I also think you're one of these sensitive kids."
The Q&A came a month after his highly-anticipated book, which details how the young Prince dealt with the death of his mum Princess Diana, was released.
Harry also hit out at his family, accusing his brother Prince William of physically attacking him and King Charles of refusing to hug him after Diana died.
The Duke’s controversial memoir has become the fastest-selling non-fiction book in the UK since records began in 1998.
Harry sat down with Dr Maté on Saturday March 4 to discuss living with loss and the importance of personal healing.
As well as a renowned speaker, Dr Maté is the author of The Myth of Normal: Trauma, Illness, & Healing in a Toxic Culture, a book investigating the connection between mental and physical health.
Harry’s late mother, Diana, Princess of Wales, died in a car crash in Paris in 1997 when the duke was just 12 years old.
In Spare, which was written with the help of a ghost writer, Harry described how difficult it was to deal with her death and he described the princess as his “guardian angel” and said she is with him “all the time”.
Harry’s grandmother, the late Queen, died in September 2022, the year after the death of his grandfather, the Duke of Edinburgh.
The duke and his wife, Meghan, have also spoken about the baby they lost when the duchess suffered a miscarriage in the summer of 2020, a year after her first son Archie was born.
During the event the Prince answered pre-submitted questions from the audience which were read out by the moderator.
Tickets costed £17 plus a £2.12 fee for UK customers, which included a copy of the book.
Harry hasn't revealed how much cash he made from the book, however he has given some of the profits to charity.
The memoir, which hit the shelves on January 10, broke the previous record of 210,506 set by the first Pinch Of Nom cookbook – written by Kay Allinson – in 2019.
Spare, which was ghostwritten by JR Moehringer, is the only non-fiction book to make it into the top 10 fastest-selling books in the UK since records began.
The March event was produced by Random House, the publisher behind Harry's book' in partnership with Barnes & Noble, Waterstones and Indigo Books & Music.