Small children, small problems. Wisdom has it that children are most labour-intensive in their infant and toddler years, but are most challenging psychologically in the teenage years.

With the Leaving Cert comes a collective sigh of relief from parents who think: "Finally, I've launched my child into the world."

Should you rest easy just because your child has got that coveted place in UCD, TCD, DCU, UCC, UCG, UL . . .?

Maybe not. Once your children reach the 17-25 year age group they need you as never before - not just to provide stability, but to help them make the right choices. "Thresholders" is the term for this vulnerable age group coined by Terri Apter, in her book, The Myth of Maturity: What Teenagers Need from Parents to Become Adults, which will be published tomorrow.

"At no time in the life of a parent is understanding a daughter or son more difficult," Apter writes.

Apter, a social psychologist at Cambridge University, is the author of several widely acclaimed and ground-breaking books, such as The Confident Child: Emotional Coaching for the Crucial Decade - Ages Five to Fifteen.

"Thresholders" are people who have the world as their oyster, but don't have the confidence and life-skills to cope with the opportunities that youth and talent offer, she believes. "Despite the rosy appearance of youth bursting with potentiality, young people in the years between 18 and 24 very often feel unworthy, lost, anxious and unprepared for the rigours of adulthood," writes Apter. "They race through puberty but balk at the rites of passage of adulthood. The proliferation of paths of maturity can arrest a person in their tracks and pressure from television, films and magazines to be beautiful, clever and successful can sap a teenager's energy and self-confidence."

A study of US and European 18-24 year-olds revealed that a quarter suffered from depression, a third had contemplated suicide and a third judged their abilities at the age of 21 to be significantly lower than they had thought them to be at the age of 17. As one leading Irish child psychiatrist has described it: "Life is about coping with challenge. Adolescents commonly see suicide as an option at a time when they are learning to deal with challenges."

Dealing confidently with challenges is the major life-skill that people in the late-teens, early-20s age-group need to master.

"Thresholders" are as much in need of emotional support as their younger brothers and sisters. Yet many parents believe that, to encourage their "adult" children's new-found independence, they should tactfully withdraw emotional and practical support, thinking it best for their children to solve their own problems.

However, Apters' research - as well as her experience as the parent of a university-aged daughter - shows that young adults actually need their parents' guidance and support more than ever. Using 32 case studies, Apter outlines the often missed cues that "thresholders" give their parents when they need help, cues that often differ from those given by adolescents and children.

If they have bought into "my child doesn't need me any more" ethos, parents may miss self-destructive behaviours around alcohol, drugs, no-strings-attached sex and the "leave me alone" mentality. These are all cries for help - pitfalls on the "adult" child's route to forming a "rewarding self-identity".

"Greg" graduated having also worked as editor of the college newspaper. He thought the world outside university couldn't wait for his talents, instead he found he was a 21-year-old "nobody". He told Apter: "It suddenly hit me that I wasn't what I thought I was . . . I wasn't mature. I wasn't talented. I wasn't marketable . . . Nobody taught me how to survive as a nobody."

So what should parents do? Apter says that parental support is not about being at your children's beck and call and giving them unquestioning financial support. She focuses on offering emotional support and, most importantly, giving "essential second chances".

"Even when parents understand how difficult the threshold phase is, they are at a loss what to do. Too often, the are confined by the myth of maturity and the myth of the spoiled child. The myth of maturity is the assumption that being mature means being independent in the sense of being separate or autonomous. It is the myth that young people can only prove themselves by showing they do not need or want their parents," Apter writes.

Dealing with a young adult's problems is very different from responding to a teen, she believes. Young adults do not respond "with a child's loving awe or with a teenager's passionate, minute criticism."

Parents must be aware of "the different shapes" that loneliness, loss and confusion take, she argues. "The first, and most obvious tactic is to help relieve a thresholder's fear that this crucial relationship (between parent and child) will be lost. Being there - and being aware that even an adult daughter or son requires an active, loving presence - is essential."

Children are "attached" to their parents in profound ways - and this attachment persists despite teenagers' attempts to appear stubbornly independent. Thresholders who remain close to their parents do better at dealing with stress, loneliness and academic and career setbacks. Young people who describe their parents as "available" do better than those who describe themselves as "self-reliant".

So if you child is off to university or a career, don't be fooled into thinking that you're not needed any more. Thresholders need their parent's heartfelt belief in them. The teen who would have cringed at his or her parents' blind faith needs it more than ever when the big world beckons.