The Duke of Sussex has warned of the dangers of social media, declaring it "more addictive than drugs and alcohol" during a discussion on young people's mental health.
Prince Harry visited the YMCA in Ealing, west London, on Wednesday, and held a roundtable event with representatives from youth charities.
"There's too much negativity surrounding mental health and it must be so hard for young people to talk about it," the Duke said.
"Social media is more addictive than drugs and alcohol, and it's more dangerous because it's normalised and there are no restrictions to it."
In a post to the new Sussex Instagram account - which has broken the World Record as the fastest account to gain one million followers - a picture of Harry during the visit was shared, and he was quoted as saying: “There continues to be huge progress in smashing the stigma that surrounds mental health, but let’s keep normalising the conversation."
The Duke also spoke about Heads Together - a mental health initiative headed by the Cambridges and the Sussexes, before joining a children's ballet session as he encouraged them to take part in a "balancing challenge".
He told youngsters to "pick a spot and stare at it" as they all tried to balance on one leg in Ealing, West London.
After the challenge, Prince Harry told one girl: "You were very very good, well done," but added that they were "all fantastic".
The soon-to-be-father was also keen to discuss baby sleeping habits when he met a young mother after the dance practice.
In a touching moment, Prince Harry knelt down and spoke with Maria Ahmad, who met the Duke with her three-month-old daughter Naz.
Afterwards, Ms Ahmad told reporters: "He was so excited and happy about the baby.
"He was asking about her sleeping.
"I think he's worried about that, if the baby sleeps at night-time."
She added about meeting the Prince: "It was a nice surprise.
"He is a good person."
Meghan is expecting the couple's baby in the next few weeks.
YMCA South Ealing is part of the YMCA St Paul's Group, which provides services across London and is one of the largest in Europe.
The association provides housing for 150 young people who are dealing with a range of problems such as homelessness, mental illness, substance misuse and domestic violence.
Prince Harry spoke with three residents at the YMCA and told them: "One of the most comforting things to know is you're not alone and you're one of the more as opposed to one of the few."
"Your own experience is very unique to you but the relatability of people in this place and everybody outside is huge.
"It's hugely relatable, even more so today than it was four years ago."
During the tour the Duke also discussed the #IAmWhole campaign with young champions for mental health.
The campaign, developed by the NHS and YMCA, encourages young people to speak openly about their mental health issues.