Diagnosing ADHD in children is tricky, to say the least, but a new biomarker could give doctors additional clarity.

Many parents agonize over whether or not to medicate a hyperactive child. Even those who do so eagerly sometimes arrive at their decision at wit’s end, or at the behest of a desperate teacher.

Prescribing stimulants, which some medical experts believe can lead to addiction later in life, is a big decision for parents and doctors alike. A diagnosis of ADHD, or attention deficit hyperactivity disorder, is based on subjective questionnaires and clinical assessments. But research published in Radiology shows that a biomarker may offer a more definitive look at ADHD diagnoses and whether these medications would be useful for a particular child.

Lead author Vitria Adisetiyo, Ph.D., and colleagues used magnetic resonance imaging (MRI) scans to examine the brains of 22 children and teens with ADHD. A dozen of them never had been medicated.

The subjects with ADHD were compared to 27 healthy children in a control group. The researchers found that the 12 subjects who had never been medicated had low levels of iron in parts of their brains called the striatum and thalamus. The medicated young people had similar levels of iron to those in the control group.

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Adisetiyo, a postdoctoral research fellow at the Medical University of South Carolina in Charleston, told Healthline that iron levels can be indicators of dopamine levels. Stimulant medications like Ritalin increase dopamine levels in the brain, allowing hyperactive children to be more focused.

But dopamine, a neurotransmitter chemical, increases sensations of pleasure in the brains of people without ADHD. Side effects can include loss of appetite and a “zombie state,” Adisetiyo said.

For children truly afflicted with ADHD, Ritalin and other medications “in some cases make a miraculous difference,” Dr. Cristina Farrell of Mount Sinai Hospital in New York City told Healthline. “It’s amazing to see that happen, and it benefits the whole family.”

The medication works when the ADHD diagnosis is accurate, said Farrell, a pediatrician and professor specializing in child behavior. When it doesn’t work, or makes only a small difference, “You go back and say, ‘Did I make the right diagnosis? Why isn’t it working?’” she said.

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In the absence of biomarkers, doctors base their diagnosis on questionnaires and in-person interviews with the patient, a parent, and ideally a third person, such as the child’s teacher. Farrell said that as a pediatrician practicing at a teaching hospital, she has the luxury of spending extra time with patients and giving a “gold standard” diagnosis.

But the reality is that psychiatrists in private practice must see as many patients as possible to have a successful practice based solely on insurance reimbursement. The result is limited face-time with each child.

Primary care providers face a similar dilemma, Farrell said. “Is (ADHD) over-diagnosed? I think it is,” she said.

Farrell often explains to parents that when a child plays a video game and remains focused for a long time, it is an indicator that dopamine is stimulating their brains to help them remain on task. The idea behind stimulants is to keep them that way when they’re in English class, too, she said.

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Farrell said that while Adisetiyo’s work is interesting, it is “extremely preliminary.” She said that looking at just one part of the brain is not enough to determine a diagnosis of ADHD. “We know that when we treat patients with ADHD with stimulants, the ADHD does not always go away. It’s not like we’re curing them,” she said. “We see the meds doing something, but it’s hard to interpret the meaning of that finding.”

Adisetiyo admits that more work needs to be done, and she is currently recruiting patients for follow-up studies. She hopes to include a larger sample in which subjects have been taking medications for specific periods of time. A longitudinal study looking at subjects’ brains before and after treatment also is needed, she said.

Ideally, the best way to look at the effects of stimulants would be to measure dopamine levels directly. However, that would require using radioactive labels, which Adisetiyo said is not realistic in a clinical setting.

The publication of Adisetiyo’s research comes on the coattails of an announcement last week by pharmaceutical company Shire, maker of the stimulant drug Vyvanse. At the request of the U.S. Food and Drug Administration, Shire plans to begin clinical trials to test the drug on children as young as 4.

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