Dopamine Protein Abnormality Linked to ADHD

A genetic variant in dopamine transporters may be a factor in the development of ADHD.

Researchers from Vanderbilt University Medical Center discovered a dopamine transporter variant in two brothers with ADHD. This rare genetic variant, found only once before in a woman with bipolar disorder, causes the transporter to "run backwards." That is, the transporter behaves as if an amphetamine were present and pushes dopamine out into the brain.

Experts have long suspected a link between dopamine signaling and a variety of psychiatric disorders, including ADHD, schizophrenia, and some phobias, and the present study pursued this specific variant to uncover possible functional impairments.

The researchers found that dopamine was "bleeding out," rather than being released in individual batches, but that, surprisingly, amphetamines blocked this leak. In a normal transporter, amphetamine would function how the variant transporter acts on its own; it would cause an increase in the dopamine released into the brain.

The research sheds light on how the two most common ADHD medications, amphetamine and methylphenidate, may work to decrease symptoms, and indicates that dopamine transporters may be an important component in the development of ADHD.

The study has been published in the current issue of The Journal of Neuroscience.