Cancer treatment is more effective when the disease is caught early. Ditto for heart disease that?s treated before a stroke or heart attack. But, in mental health, most patients suffer for months or years before doctors intervene. A growing number of psychologists and psychiatrists ? frustrated with what they see as an ?epidemic? of mental illness ? say that attitude needs to change. Doctors need to know how to find mental illness in at-risk children and young adults before the symptoms become full-blown.

?In the whole history of medicine, it?s never been possible to overcome an epidemic simply by treatment. You need to have prevention,? said Gregory Clarke, a psychologist at Kaiser Permanente?s Center for Health Research in Oregon. The problem Clarke and others face is how to address an illness that has not yet manifested itself ? and may never. A number of mental illnesses, including depression, bipolar disorder and schizophrenia, are thought to have genetic components that put children at risk if the diseases run in their families.

But these children may never develop the illness, so should they sit through hours of talk therapy each month just because their mother is depressed? Should they be prescribed powerful medications with unknown side effects just because they are unusually anxious? Should doctors and schools label children as at-risk for bipolar disorder or schizophrenia when such a label is fraught with stigma?

Such questions have been at the heart of a debate prompted by a 2003 report from the President?s New Freedom Commission on Mental Health, which suggested a focus on early detection and treatment. Critics, including a Texas Congressman who has filed a bill to prohibit use of federal funds for widespread mental health screening, said mental illnesses cannot be identified with a simple brain scan or blood test, and they fear early screening will lead to overmedication of young patients.

Others support early detection efforts. ?Depression is just such a terrible illness to experience. As one mother said to me, it attacks the soul ... but you can protect children going through that experience, if you get youngsters early in the course of the illness, you have a much better chance at an effective long-term positive outcome,? said Dr William Beardslee, chief of psychiatry at Children?s Hospital Boston. He is involved with two early intervention projects for depression that are among a handful scattered across the country. They use talk therapy and group counselling to educate adolescents with depressed parents about how to keep minor problems from becoming major ones.

Depressed people are prone to a phenomenon called ?catastrophising,? several experts said. A simple negative experience such as a bad test grade or bad breakup might act as a trigger, sending a person spiralling downward. Therapy can be as simple as teaching teenagers to see such setbacks as just that ? temporary setbacks. The approach was shown to have lasting effects by a pioneering study that Clarke published in 2001, which compared at-risk teenagers who received 15 sessions of talk therapy with those who didn?t. After a year, the group that got no intervention had three times the rates of depression as the group that did receive therapy. The treatment is now being duplicated at some schools and at four test sites around the country, including Boston.

Mood genes: Depressive mothers can pass on their problems to their babies

Even if ?it?s just delaying [the onset of depression], that?s a benefit,? Clarke said. Because the risk for developing clinical depression is greatest when people are 15 to 25 years old, a prevention programme may be able to keep them healthy until they are out of the window of risk, he said. Research at this point focuses mainly on those at known risk of depression because of age or family history, or special cases like women who have just given birth.

Ricardo Mu?oz, a psychologist at San Francisco General Hospital, works with postpartum mothers to prevent depression and help them interact with their child. Studies have shown, he said, that depressed mothers may pass on their problems to their babies by some combination of genes and interaction. ?There?s something that happens to babies of depressed mothers fairly fast so that if the mother is depressed for a good chunk of time, this could have an impact on how the baby learns how to respond to stress, even learns how to feel.?

As more and more mental illnesses are thought to show signs early in childhood, researchers are also beginning to work to get to children as soon as feasible. Dr Joan Luby, a psychiatrist at the Washington University in St Louis, works to uncover mental illnesses in preschool-age children by having youngsters watch two puppets interact and asking them to identify with one of the characters.

Schizophrenia researchers have identified a number of ?prepsychotic? symptoms in teenagers thought to be the early signs of the disease. The Child and Adolescent Bipolar Foundation last month issued guidelines for mental health professionals attempting to diagnose bipolar disorder in children, which may have different symptoms than the adult form. Some prevention programmes for these less common mental illnesses can be more controversial. Some programmes use therapy in combination with medication, under the theory that it could be possible to stave off the illness altogether, or lessen its intensity. But the medications sometimes used ? antipsychotics, antidepressants, and other psychiatric drugs ? have been linked to harmful side effects, including suicide and diabetes.

On the other hand, the risk might be worth it. ?Why wait five or six years for these symptoms to wreak havoc, to have a neurobiological effect? You wouldn?t think of leaving seizure disorder for years, because they generalise, they move from one side of the brain to the other,? said Dr Timothy Wilens, a paediatric psychopharmacologist at Massachusetts General Hospital who does drug-based interventions with at-risk children, some preschool-age.

He noted that the greatest problems parents face is a lack of resources: Few doctors are trained to detect precursors of mental illnesses early in life, or know what to do if a serious risk does exist. Betty Ruth, a social worker at Boston University, campaigned vigorously for prevention services in Massachusetts in 2001 ? not as part of her job, but because as a mother of a depressed daughter she feared that her son might also be at risk. ?Parents should be able to turn to the system and say, ?I?ve got one kid who?s depressed,?? and expect to get help.