By Stephanie Stahl

PHILADELPHIA (CBS) — Mental disorders affect nearly 12 percent of the world’s population, which is about 450 million people.

And Tuesday marks the 25th anniversary of World Mental Health Day.

READ MORE: Northeast Philadelphia Native Jasmine Martinez Will Represent Flyers In Montreal NHL Draft

In Britain, Prince William and his brother Harry are teaming up with health advocates to encourage people to talk about their problems instead of suffering in silence.

The young royals are promoting well-being through their “Heads Together” campaign.

During their official visits Princes William and Harry started noticing many people were struggling with mental health issues.

“At the core of adult issues like addiction and family breakdown, unresolved childhood mental health issues were often part of the problem,” Prince William said.

For this World Mental Health Day, many British people are abandoning the traditional “stiff upper lip” for more open conversations about mental illness.

READ MORE: Buildings Designated Unsafe After Partial Collapse in West Oak Lane, City Spokesperson Says

This is just one of hundreds of “Tea and Talk” events — where people can speak honestly.

“My self-esteem has always been, sort of, on the floor, and that kind of permanently berating myself through the voice that never, ever shuts up,” Roxie Nafousi, who suffers from anxiety & depression, said.

Experts say millions of people around the world have a variety of mental health conditions, with depression being most the prominent.

“There is still a stigma attached to talking about mental health struggles,” Med-depression screening counselor Dana Careless said.

Careless says a recent study showed many teenagers are also struggling.

MORE NEWS: Camden County Health Officials Contact Tracing After Resident Tests Positive For Monkeypox

Over 30 percent of Philadelphia High School students reported feeling hopeless or helpless for 2 weeks or more. That’s higher than the national average.

Stephanie Stahl