More than half of young people who experience stigma due to mental health problems say their own friends are the ones who bully them.
A new poll of more than 2,000 11 to 24-year-olds for the YMCA found 38% felt stigmatised, with more than a third saying it happens at least once a week and 54% saying it originates from their own friends.
Types of stigma included being left out of activities (54%) and verbal abuse (36%). Most of those affected said it damaged their school performance and confidence.
The YMCA is backing the #IAMWHOLE mental health campaign, which is being fronted by celebrities including presenters James Corden and Dermot O'Leary and singer Ed Sheeran.
The campaign aims to change how people describe mental health issues and urges young people to ask for support from their friends, parents, teachers, GPs or youth workers.
Denise Hatton, chief executive of YMCA England, said: "YMCA's research backs up conversations we have had with young people in which they have told us mental health is one of the principle worries affecting their generation today.
"What is alarming from these findings is the widespread stigma young people are now seeing or experiencing from others that is making them less likely to seek professional help."
Dr Tim Kendall, national clinical director for mental health for NHS England, said: "A lot of work is being done by the NHS in England to support improvements in children and young people's mental health and wellbeing, including major investment and service transformation over the next five years.
"Reaching out to young people who aren't coming forward to access services due to fear of stigma is so important and the #IAMWHOLE campaign is helping to start that conversation with young people today online, through social media and an anti-stigma challenge initiative for schools."
The survey comes as a separate poll of more than 1,200 youngsters aged eight to 15 for mental health research charity MQ found 49% thought a diagnosis of mental health problems might mean never getting better.
Some 56% of young people said they thought that if a classmate the same age developed a condition they would be treated differently, 55% thought they would lose friends and 51% would feel embarrassed.
New figures from the charity also show that mental health research funding across all age groups in the UK is just £8 per person affected each year.
It said this is 22 times less than that spent on cancer and 14 times less than dementia.
Cynthia Joyce, chief executive of MQ said: "We can no longer accept the status quo in mental health. Radical change is needed. If we don't take action now, this imbalanced situation will continue to let down millions of children and young people.
"Through research, we've seen extraordinary advances in healthcare that were once unimaginable. We need to be just as ambitious about mental health, and implement long-term action."