ADHD Medication Rendered Impotent?

April 1, 2012 § Leave a comment

Studies in the United States indicate that approximately 8-10% of children meet the diagnostic criteria for ADHD. It is therefore one of the most common childhood disorders. Many think children will outgrow this disorder, but recent studies reveal that many will continue to experience symptoms throughout their lives, into adulthood. These symptoms may affect both occupational and social performance.

Common medications for the treatment of ADHD are psychostimulants like methylphenidates (Ritalin, Metadate, and Concerta), amphetamines (Dexedrine, Vyvanse, and Adderall), and atomoxetines (Strattera).

A recent study led by Dr. Paolo Fusar-Poli and Professor Katya Rubia, performed at the Institute of Psychiatry (IoP) at King’s College London, reveals that the brain appears to adapt to ADHD medications in the long-term. This study was published in the American Journal of Psychiatry.

Professor Rubia said, “There is currently no evidence for the long-term effectiveness of stimulant medication. In fact, there is evidence that the effect of medication diminishes over time and we know from clinicians that medication doses often need to be increased over time to be as effective as they were initially. Our findings could help explain why stimulants work very well in the short term but not so well long-term.” The findings suggest that ADHD medication is more useful in the short-term.

ADHD is linked to deviations in the dopamine system. Dopamine is a chemical that affects motivation and attention. Patients with ADHD have low levels of dopamine. Ritalin and other such medications block uptake of dopamine in the brain, leaving more available.

Conversely, measuring the exact levels of DAT in the brains of ADHD patients had revealed contradictory results. Early Positron Emission Tomography (PET) and Single Photon Emission Tomography (SPECT) scans revealed DAT levels were elevated in the basal ganglia in ADHD patients, but later studies found them to be reduced. The research team endeavored to elucidate this contradiction.

They performed a combined analysis of 9 SPECT and PET studies to observe levels of DAT in 169 ADHD patients and compared them to a control group of 173 healthy individuals. Most were focused on adults.

The researchers found that the DAT levels in ADHD patients was associated with whether or not the patients had been taking long-term medication. Patients who did not take stimulants had unusually low DAT levels. Contrarily, patients who had received long-term medication had elevated DAT levels. These findings suggest that the brain builds up more DATs to adapt to stimulants to compensate for the high levels of dopamine. The DATs eliminate the dopamine. Also, this means that increased DAT levels in ADHD patients is the result of long-term medication and is therefore not always attributable to ADHD itself.

The team expresses that more long-term studies must be performed in order to examine the long-term effects of the adaptation.

 

Sources

Mersch, John. “Attention Deficit Hyperactivity Disorder (ADHD) (ADD)”. Medicine Net. March 11, 2012. http://www.medicinenet.com/attention_deficit_hyperactivity_disorder _adhd/article.htm.

“Patients’ Brains May Adapt to ADHD Medication”. (February 2, 2012). Neuroscience News. March 11, 2012. http://neurosciencenews.com/adhd-medication-patient-brains-adapt-dat/.

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