74% of 11-18 year olds are aware of the risks of smoking cannabis
Nearly one in two teenagers knows someone who has suffered from a mental health problem like paranoia after using cannabis, a survey suggests.
Forty-two percent of 11-18 year olds know someone who has experienced memory loss, panic attacks or paranoia from cannabis, drugs information service Frank said.
The survey of 27,000 teenagers found 74% were aware of the risks.
It revealed 18% of teenagers felt under pressure to try the Class B drug.
One in ten thought it made them look cool.
The research, which was carried out on networking website Habbo Hotel, found 64% of young people were aware cannabis could cause panic attacks, 41% knew it could bring on paranoia and 38% thought it could result in memory loss.
Over 50% of teenagers associated cannabis use with losing motivation and doing badly at school or college.
But one in four said they saw cannabis as a "natural" drug, despite the risks.
And 14% of 11-18 year olds admitted using the drug to help them to cope with life.
Chris Hudson, from Frank, said: "The majority of teenagers (55%) don't want to risk their health by using cannabis, however, some people choose to take the risk; while others wrongly believe cannabis is harmless because it is a plant.
"Cannabis messes with your mind - and reactions can be more powerful with stronger strains such as skunk, which is around twice as potent," he warned.