What every parent and adult needs to know

Report By: Researchers at Brookhaven National Laboratory

For many years, dopamine, a neurotransmitter (a brain chemical that transmits a message from a brain cell to another brain cell), was thought to be primary culprit in ADHD. Dopamine plays a major function in the brain as it is responsible for reward-motivated behavior. A plethora of studies have shown rewards increase the level of dopamine in the brain. This is what makes us motivated to get rewarded. Many drugs, including cocaine, Ritalin, and methamphetamine, act by amplifying the effects of dopamine. Too little dopamine means greater distractability and riskier behavior as the brain constantly seeks ways to increase its dopamine levels.

Researchers at Brookhaven National Laboratory published a study in the journal PLOS One examining levels of dopamine in ADHD patients who had never taken stimulants. They reviewed dopamine transporter density. Transporters actually filter dopamine away from its receptors in the brain. More transporters means less dopamine (and therefore less bang for the reward). Transporter density was determined through PET brain scans.

Initial scans found no differences among their small population of 18 adults who suffered from ADHD but were never treated for it. This group was then treated with Ritalin. After a year, the researchers discovered that dopamine transporter density increased by 24 percent. What this study found was in fact what many parents have discovered during their child’s use of medication; taking ADHD medication may change the brain’s chemistry so that the effects of the medication are reduced over time. To accommodate this, one’s pediatrician or medical doctor will often increase the dosage due to drug tolerance.

More questions than answers arise due to this research. Here’s what’s now on the table:

* Medication is commonly taken over many years. The researchers are not sure whether the brains would return to their original state if they stopped taking the drug.

* Other studies have indicated that increased levels of dopamine transporters in the brain could be used as a diagnostic marker for ADHD — a way to screen for ADHD. This research tells us that long-term use of stimulant medications like Ritalin may actually cause these increased levels. So increase levels is not a good biomarker.

* Long-term effects are now questionable; will the medicated person constantly need more risk-associated behaviors including drug use as the effects of medication are reduced over time?

“In this study, we only proved that increased dopamine transporter levels cannot be used as a biomarker,” Wang said.

One of the patients in Wang’s study who had never received ADHD therapy was having difficulty in college and in her marriage, but she loved to paint. After taking medication she did better in school and with personal relationships, but she lost her creative drive, Wang said.

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