DOCTORS and parents have long been left to guess at which children with a diagnosis of attention-deficit hyperactivity disorder, or ADHD, will go on to become adults with significant attention problems, how well they will navigate the challenges of adulthood and whether early recognition of—and medication for—their condition will make a difference in the trajectory of their lives.

Now a series of studies following 457 Finnish children from birth to ages 16 to 18 offers a glimpse of how the primary symptoms of ADHD typically evolve. At the same time, the studies raise provocative questions about the long-term effect of treating those symptoms with medication.

The studies focus on a subset of 188 Finnish teens considered to have “probable or definite ADHD” that will follow them into adulthood and 103 kids with conduct disorder—behavior issues that fall short of an ADHD diagnosis but put kids at higher risk for similar problems. Those teens were compared with a group of Finnish teens with no ADHD diagnosis.

Researchers found it is the can’t-sit-still kids—the stereotype of the “ADHD generation”—who are most likely to mature out of the disease. Among those with persistent ADHD, they also found, half have problems with cognitive skills that are key to success in adulthood, but half have no such deficits.

And when researchers compare the findings from Finland with studies of Americans with ADHD, an even more intriguing discovery emerges: By the time they’re in their late teens, those who receive drugs for attention problems seem to fare about the same as those who do not.

That is sure to fuel a simmering debate over the extent to which American kids with ADHD receive medication, often with little other support. In Finland medication for ADHD is extremely rare.

“This begs the question: Are current treatments really leading to improved outcome over time?’” wrote neuropsychologist Susan L. Smalley and coauthor Dr. Marjo-Riitta Jarvelin in a special section of December’s Journal of the American Academy of Child & Adolescent Psychiatry. Smalley codirects the Center for Neurobehavioral Genetics at the University of California, Los Angeles. Jarvelin is a professor of public health and of medicine at Imperial College School of Medicine in London and University of Oulu, Finland, respectively.

UCLA neuroscientist Robert Bilder, who was not involved in the Finnish research, said the studies suggest that ADHD might best be treated, in some kids, by shoring up weaknesses in underlying cognitive skills rather than by focusing exclusively on behavioral symptoms that can change with age.

“We all hope in the future we’ll find the optimal combination of treatments—whether behavioral or pharmacological—that’ll provide young people with these problems the best chance to succeed in school and social environments,” Bilder said. “It’s clear so far that no treatment’s been identified that’s a panacea.”

Two decades ago, as the diagnosis and medication of American children with ADHD began to soar, researchers and psychiatrists scarcely entertained the possibility of adults with ADHD. Today experts estimate that 4.4 percent of American adults—more than 10 million people—suffer from attention problems serious enough to warrant a diagnosis of ADHD.

But like the generation of children first diagnosed in large numbers with ADHD, research on what the disorder looks like across the life span has just begun to mature.

The new research suggests that, as children with ADHD grow into adolescence, it is the dreamy, forgetful, inattentive types who are most likely to continue to struggle with the disorder—especially if they also suffered from depression, anxiety or serious behavior problems in their preteen years. When their childhood symptoms included hyperactivity and impulsiveness as well as inattentiveness, their chances of having adult ADHD grew higher still.

Underscoring the strong role of genes in the development of attention deficit disorders, the studies found that a child’s likelihood of having ADHD that persists into adulthood is significantly greater if either parent—but especially his or her father—suffers from serious attention problems too.

By contrast, those whose childhood symptoms were confined to hyperactivity are the most likely to mature out of the disease in adolescence, the Finnish studies found. By age 18, most with persistent ADHD will struggle with mental rather than physical restlessness.

In all, roughly two in three of the Finnish children who were diagnosed with ADHD as children continued to exhibit severe attention problems between ages 16 and 18.

In an introduction to the special section, Smalley points out several similarities and one intriguing difference between the Finnish children who were studied and their US counterparts. ADHD appears with similar frequency in each of the two populations. Each population also has similar variations in symptoms of the disorder and similarly high rates of social and emotional problems—depression, anxiety, defiant behavior—that often afflict adolescents and adults with ADHD.

In Finland, as in studies of US populations, about half of older teens with persistent ADHD performed poorly on tests of short-term, or working memory, and in cognitive skills that are key to problem-solving, making plans and executing tasks. And in each group, roughly the same proportion of children “mature out” of the disorder.

Although about 60 percent of American children diagnosed with ADHD are medicated—at least at some point—for its symptoms, virtually no Finnish children are given medication. And yet, by the time they reach 16 to 18 years old, these two populations look very much the same.

In an interview, Smalley stressed that the studies do not cast doubt on the short-term benefits a child with ADHD might get from a stimulant or other medication that treats the symptoms of the disorder. She cited recent studies showing that at the end of one year, children medicated for ADHD symptoms function better at home and school than those who get behavioral and cognitive therapy. But after three years, the difference between the two groups begins to wane.

“We really need to look at how effective, really, is medication alone in long-term prevention” of the intellectual deficits and psychiatric problems that plague those with ADHD at higher rates than those without, Smalley said.

She also emphasized that the studies show that ADHD is “an extreme on a continuum” of normal for humans. Just as kids range across a spectrum in glucose tolerance or reading ability—putting some at higher risk of diabetes or dyslexia—they are also distributed across a spectrum in terms of their ability to focus, the strength of their working memory and their propensity for developing social and emotional problems. As children age, some will “age out” of the disorder, no longer meeting diagnostic standards for ADHD.

If better medication or specialized therapy, or both, can drive down the risks that these children will be hobbled by academic failure, ill-chosen impulses and other psychiatric problems, their other talents could shine through, Smalley said. And the world would be a better place for it, she added.

“We need to step back and embrace neurodiversity, diversity in human behavior and try to work on ways to embrace and enhance being at the extreme, instead of only focusing on the deficits and disorder aspects of ADHD,” Smalley said.

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