The Duke of Sussex has said he used to drink a week’s worth of alcohol in a day to try to deal with the trauma of his mother’s death.
Prince Harry was also willing to take drugs to “feel less like I was feeling” more than a decade after she died.
The duke was talking to US talk show host Oprah Winfrey in their new streaming series on mental health.
He also spoke of the anxiety and panic attacks he had as a senior royal, and his experience of his mother’s funeral.
Diana, Princess of Wales, died in a car crash while being pursued by photographers in Paris in August 1997.
Speaking to Oprah for the Apple TV series The Me You Can’t See, Harry described being aged 28 to 32 as “a nightmare time in my life”, in which he had panic attacks and severe anxiety.
“I was just all over the place mentally,” he said.
“Every time I put a suit on and tie on… having to do the role, and go, ‘right, game face,’ look in the mirror and say, ‘let’s go’. Before I even left the house I was pouring with sweat. I was in fight or flight mode.”
He added: “I was willing to drink, I was willing to take drugs, I was willing to try and do the things that made me feel less like I was feeling.”
He said he would drink a week’s worth of alcohol on a Friday or Saturday night, “not because I was enjoying it but because I was trying to mask something”.
Prince Harry famously walked behind his mother’s coffin at her funeral, alongside his brother, father, uncle and grandfather.
“For me the thing I remember the most was the sound of the horses’ hooves going along the Mall,” he said.
“It was like I was outside of my body and just walking along doing what was expected of me. Showing one tenth of the emotion that everybody else was showing: this was my mum – you never even met her.”
The prince, 36, has campaigned for discussions around mental health to be normalised, and started speaking in detail about his personal experiences recently.
In March, he and his wife Meghan were interviewed by Oprah about their life in the Royal Family, and its impact on their mental health.
And on a podcast last week, Prince Harry said he was determined to “break the cycle of pain” of his upbringing when parenting his own children, and shared that he had gone to therapy.
The duke said the happiest time of his life was his 10 years in the Army, as there was no “special treatment” for him.
He left the Army aged 30, and met his wife-to-be Meghan on a blind date a year later.
The duke said family members previously told him “just play the game and your life will be easier”.
“But I’ve got a hell of a lot of my mum in me,” he said. “I feel as though I am outside of the system – but I’m still stuck there. The only way to free yourself and break out is to tell the truth.”
The streaming series sees Prince Harry, Oprah, Lady Gaga, Glenn Close and others tell their own stories about mental health and wellbeing.
It was first announced in April 2019, almost a year before Harry and Meghan announced they were stepping back as senior royals in January 2020.