But the apparent finality in this information should not be cause for despair. First of all, these studies have been challenged on some of their assumptions and methodologies. And, regardless of its reliability, this data confirms that genes are not the exclusive dictators of destiny. In pairs of identical twins, both twins develop schizophrenia half of the time, but in 50 percent of cases, only one twin develops the disorder. Since these twins have exactly the same genes, only the differences in their individual experiences or environment can explain why, in the discordant pairs, one twin became schizophrenic and the other did not.

And while hereditary personality factors contribute strongly to an ADHD profile, the line between an extreme in normal personality, and a full-blown disorder, is still determined by family and culture. Children with ADHD in genetics studies are well screened and generally more extreme than garden-variety, spirited children struggling in a suburban school. And the child who lives in Boston is more likely to be considered a problematic candidate for medication than the one in Honolulu because of cultural and child-rearing factors.

Essentially, parents can help balance the power of heredity, but never erase it completely. Psychologist Judith Harris tries to explain this complicated alchemy in her controversial book "The Nurture Assumption." She was excoriated in some quarters for purportedly saying that nature determines behavior so definitively that "parenting doesn't matter."

But a closer read of her book reveals that even Harris believes that parenting styles do matter. To paraphrase, she says it would be very naive on your part to think, upon marrying your spouse, that you could fundamentally change his or her personality. However, how you behave with one another can have a major influence on how well the two of you get along.

The same principle holds true in raising children, according to Harris. While you are unlikely to influence long-term outcomes for your children when it comes to interests, educational level and, dare I say, mental illness or health, the way you behave with them as they grow can make a huge difference in your daily life together -- how well you get along, how close you are, how much you fight with your child.

In other words, it's up to you to adapt to your child's personality -- to have certain expectations and responses that are compatible with your kid's personality needs. Temperament theorists call this a "goodness of fit." Children with goodness of fit in their families have less psychiatric problems, at least through mid-adolescence. (Little reliable data exists for outcomes in adulthood.)

Of course, when I suggest adapting to your child's personality, I don't mean that you must give in to your children's demands. In fact, for a child with a very persistent and intense personality, a good fit may mean that you need to take a steady and firm stance in the face of his or her strong challenges. A child with a shy or inhibited personality will do better if you are sensitive but do not excessively rescue or protect your kid from facing the stresses of normal life.

When it comes to an adopted child with a troubled or unknown genetic pedigree, the parents are definitely taking on an extra challenge. Genes are not the only culprit in difficult or dangerous behavior, but it would be somewhat naive to think that a loving and stable home could overcome every personality-based problem a child inherits. Adopted children do have more psychiatric problems -- they are in treatment twice as much as children who live with their birth parents. A combination of genes and adoptive family dynamics appears to contribute to this higher incidence of problems.

On the other hand, studies also show that children adopted by families with socioeconomic advantages have IQs up to 10 points higher than they would be expected to have if they stayed with their biological parents. And a stable loving home seems to be a major attenuating influence on the rates of criminal behavior among adopted children whose biological parents were also engaged in criminal behavior.

At this stage in her daughter's life, I doubt there is any specific answer or solution for this writer and her child. Genetic determinism can be seen to absolve parents and children of any blame in troubling behavior, but it carries with it a whiff of fatalism and belief in a lifelong stigma that I'm not sure is justified or moral.

I think it still makes sense for this mom to search for strategies and ways to be involved with her teenager and to provide help and emotional support until her daughter is making wise decisions on her own. And given the difficulty of this task, the writer should find support of her own -- she deserves it.

Most importantly, KS should not blame herself (or her daughter) for the problems they've experienced. Hereditary factors are a hurdle, but in appreciating her child's unique personality, and finding the most appropriate responses to her behavior, she can help tip the balance in her child's journey to adulthood, turning an unpleasant slog into a rewarding adventure.

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