Self-harm, suicide attempts, depression, over-eating, excessive sleepiness, phobias and panic attacks may be some of the signs that all is not well.
'Emotional disorders are often not recognised, even by family and friends,' the college warned.
In a guide to adolescence, published yesterday, the college seeks to raise public awareness of problems which spring from rapid physical and mental change in young people, whose families may be ill-equipped to deal with them.
Michael Shooter, a child and adolescent psychiatrist, said: 'Eating disorders have rightly been getting a lot of publicity lately.
'Adolescents have been expressing their upset for a long time and it is about time we paid more attention to conditions that are potentially life-threatening.'
He said that 15 per cent of teenagers who attempted suicide would try again and, of this minority, 1 per cent would kill themselves within three years, and 3 per cent within five years.
Dr Mollie McBride, honorary secretary of the Royal College of General Practitioners, said that family doctors might be missing adolescent problems because of the tradition that children should only see the doctor accompanied by an adult.
Some parents were inclined to dismiss problems as a food fad or temper tantrums, not serious enough to warrant a visit to a family doctor, she said. In any case, a teenager might not be keen to speak to a doctor for fear that parents might be told about the consultation.
Dr McBride highlighted research by Dr Chris Donovan, a north London GP, who had started health promotion clinics for 16-year olds.
'He found that 10 per cent needed immediate medical treatment and that 25 per cent of boys and 14 per cent of girls were smokers already.
'One third of those attending did not realise that consultations were confidential from their parents once they were over 16.'
The RCP guide urges parents to see the arguments that may accompany adolescence as not necessarily meaning their parenting is flawed.
'Parents often feel rejected, and in a sense they are. But this apparent rejection is necessary for young people to become adults in their own right . . . The rejections and conflicts are often not to do with parents' personalities but simply the fact that they are parents, from whom their children must become increasingly independent if they are to have their own life.'
Surviving Adolescence; Royal College of Psychiatrists, PO Box 19, Basingstoke, Hants RG26 5BR.Reuse content