Science/Tech

Long-Term Treatment For ADHD May Lead to Changes in Brain Chemistry

By Makini Brice | Update Date: May 16, 2013 02:15 PM EDT

An adult woman who had never received therapy for her attention deficit/hyperactivity disorder (ADHD) loved to paint, but had difficulty with her marriage and with her college courses. After she was treated with medication for year, her ability to perform academically and to interact in her personal relationships improved, but her creative drive disappeared.

Her story - told when she was part of a recent study on ADHD - is not unusual, but it may indicate a need to reconfigure how physicians and scientists address ADHD. According to Healthline, ADHD is typically diagnosed through a variety of behavioral systems. It has previously been believed that people with ADHD had greater numbers of dopamine transporters. Dopamine, a neurotransmitter, has been held responsible for attention and pleasure; transporters are responsible for filtering them out of the brain. Therefore, it was believed that people with ADHD have more of these transporters, and that is why the condition is often manifested through performing risky behaviors that elevate dopamine.

However, a recent study has found that the targets of ADHD medication may have been wrong. In fact, the study indicates that taking ADHD medication, like methylphenidate, which is commonly sold as Ritalin, may change the brain's chemistry. The research indicates that, as a result of long-term use of the drug, the brain may change in order to make it less effective, in turn causing users to build up a tolerance to the drug.

The study was performed by examining 18 adults who suffer from ADHD and who had never been treated for it. Because most children who suffer from ADHD do receive treatment, it makes it difficult to find adults who have never been treated for the condition if they have it, which is why the sample size is so small. The adults had their brains scanned at the beginning of the study, and then a year after they took Ritalin. These adults were compared with a control group of adults who did not have any neurobehavioral disorders.

While the first scan did not reveal any difference in the number of dopamine transporters between the subjects with ADHD and those without, the second scan a year later did. According to My Health News Daily, the study found that taking the drug for a year increased the number of dopamine transporters by 24 percent, while the controls had no difference in their brains. Researchers are not sure whether the brains would return to their original state if they stopped taking the drug; nevertheless, the finding represents a conundrum, as most people who take stimulants for ADHD do so for a long period of time.

"Upregulation of dopamine transporter availability during long-term treatment with methylphenidate may decrease treatment efficacy and exacerbate symptoms while not under the effects of the medication," the researchers write.

The study was published in the journal PLOS One.

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