What Does Research Show About the Effects of ADHD Medication?

By Child Mind Institute, Understood Founding Partner

I’m thinking of putting my 8-year-old on ADHD medication. What do long-term studies of children on ADHD medications show?

Many parents are concerned about the effects of medications for treating ADHD. These drugs are usually stimulants. And kids often take them for years.

An Accurate Diagnosis

Before you consider medication, be sure your child has gotten an accurate diagnosis from a professional trained and experienced in child and adolescent mental health. If medication is being prescribed, make sure your doctor has the time to carefully determine the best dose and monitor your child over time.

Basics of Stimulants

The stimulant medications prescribed for ADHD are short-acting. They don’t stay in the body for long. That means that they stop working when he stops taking them. Any possible side effects, like loss of appetite or trouble sleeping, also stop when he stops taking the medication.

Research on Effectiveness

Stimulant medications have been prescribed for ADHD for more than 40 years. There is a lot of research showing that they are safe and effective for reducing the symptoms of ADHD. There are a number of controlled studies of ADHD. Some compare results of treated and non-treated kids. Others compare those treated with medication and those who get behavioral therapy.

The largest of the controlled studies, called the MTA (or Multi-Modal Treatment Study of ADHD) study, treated nearly 600 children in the late 1990s for 14 months. The longest treated over 100 kids for two years. Both found that kids treated with stimulant medications had their symptoms significantly reduced. Medication had a more powerful effect than behavioral therapy.

Research on Long-Term Effectiveness

Some studies followed children with ADHD for longer periods, even into adulthood. But the kids in these studies are not being treated in a systematic, scientifically controlled way. So the results are not conclusive.

There’s no way to know what kind of care they are getting or how many of them really stick with the medication. In addition, some kids outgrow their symptoms as they go through adolescence. Those who stay on medication longest may be those who had the most severe ADHD symptoms to begin with, so the results are skewed.

Some researchers believe that follow-up studies of kids in the MTA study show that the effectiveness of medication declines and disappears when it’s taken longer than two years. But others consider these results meaningless since the use of medication wasn’t controlled or monitored after the first 14 months. And by the time kids are adolescents, few of them take their medication consistently.

Research on Long-Term Safety

A number of studies have followed children with ADHD for longer periods. None has turned up any negative effects in kids whose parents reported that they were taking medication.

Rachel Klein, Ph.D., professor of psychiatry at the New York University School of Medicine, and a group of colleagues did a two-year controlled study of more than 100 school-age kids back in the late 1970s. They then followed up with them repeatedly over 33 years. Most are now 41 years old. Those who took ADHD medication showed no negative effects in terms of medical health or other functioning, compared to those who didn’t.

Dr. Klein notes that we don’t know for sure the long-term effects of this medication on the brain. It’s difficult to treat patients in a scientifically systematic way for a long time and measure the results. But she adds that parents have to weigh the unknowns of long-term use against the known risks of not treating ADHD in children: a higher rate of school failure, conflict with parents and authorities, and dangerous behaviors.

According to Ron Steingard, M.D., a child and adolescent psychiatrist at the Child Mind Institute, doctors report unusual side effects or problems their patients encounter to drug companies in what are called “post-marketing surveys.” Over four decades, he notes, nothing significant in terms of long-term effects has surfaced.

ADHD Medication and Growth

There is evidence that taking ADHD medications, which can suppress a child’s appetite, can affect a child’s physical development. Several studies in the last 10 years show that children on medication for as little as three years are behind other kids by as much as an inch in height and 6 pounds in weight.

But a new study last year looked at kids over a period of 10 years and found no differences in height or weight between those who had taken stimulant medications and those who hadn’t. Differences were most noticeable in the first two years. But most kids on ADHD medications caught up with other kids over time. And kids who took what parents call a “drug holiday” over the summer or on weekends did not show the lag in growth.

Problems Later in Life?

Stimulant medications are not considered habit-forming in the doses used to treat ADHD. There is no evidence that their use leads to substance abuse.

Still, substance abuse is, and should be, a big concern for parents of kids with ADHD. A recent study showed that teens and young adults with ADHD are at higher risk for substance abuse than other kids. But treating them with stimulant medications doesn’t increase the risk. What the new study shows is that the risk is linked to the disorder, not to the treatment.

Long-Term Effects on the Brain?

ADHD medication changes levels of brain chemicals called neurotransmitters. Studies using brain scans to look at kids who had been treated with stimulant medications have found changes in the brain related to the medication and to those neurotransmitters. The number of “targets” for the medication was increased in kids who had been on stimulant medications, compared to other kids.

Some scientists think the increase in density of those targets could be an effect of the brain adapting to the effects of the medication. This could make sense, since in some kids the medication doesn’t work as well over time. They need an increase in dosage to get the same results.

So it’s possible that use of stimulant medication does have some effect on brain functioning after a child stops taking it. But we don’t know enough about what effect that might be to know if it has any consequences. And we do know that not treating ADHD has serious long-term effects, including increased risk of failure in school, conflict with authorities, and other risky behavior.

In any case, ADHD medication has been proven helpful for kids when it matters. “Lots of good medications become ineffective eventually,” says Child Mind Institute scientist Michael Milham. “That doesn’t mean we don’t use them for as long as they work.”

About the Author

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Child Mind Institute, Understood Founding Partner is dedicated to transforming mental health care for children everywhere.

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