Depressed Dopamine Activity in Caudate and Preliminary Evidence of Limbic Involvement in Adults With ADHD

ABSTRACT

Context Attention-deficit/hyperactivity disorder (ADHD) is the most prevalent psychiatric disorder of childhood. There is considerable evidence that brain dopamine is involved in ADHD, but it is unclear whether dopamine activity is enhanced or depressed.

Objective To test the hypotheses that striatal dopamine activity is depressed in ADHD and that this contributes to symptoms of inattention.

Design Clinical (ADHD adult) and comparison (healthy control) subjects were scanned with positron emission tomography and raclopride labeled with carbon 11 (D2/D3 receptor radioligand sensitive to competition with endogenous dopamine) after placebo and after intravenous methylphenidate hydrochloride (stimulant that increases extracellular dopamine by blocking dopamine transporters). The difference in [11C]raclopride's specific binding between placebo and methylphenidate was used as marker of dopamine release. Symptoms were quantified using the Conners Adult ADHD Rating Scales.

Setting Outpatient setting.

Participants Nineteen adults with ADHD who had never received medication and 24 healthy controls.

Results With the placebo, D2/D3 receptor availability in left caudate was lower (P

Conclusions This study reveals depressed dopamine activity in caudate and preliminary evidence in limbic regions in adults with ADHD that was associated with inattention and with enhanced reinforcing responses to intravenous methylphenidate. This suggests that dopamine dysfunction is involved with symptoms of inattention but may also contribute to substance abuse comorbidity in ADHD.

Thank you to the Archives of General Psychiatry, August 2007. This is the Abstract. The entire article is made free to readers online at http://archpsyc.ama-assn.org/cgi/content/full/64/8/932

Nora D. Volkow, MD; Gene-Jack Wang, MD; Jeffrey Newcorn, MD; Frank Telang, MD; Mary V. Solanto, PhD; Joanna S. Fowler, PhD; Jean Logan, PhD; Yeming Ma, PhD; Kurt Schulz, PhD; Kith Pradhan, MS; Christopher Wong, MS; James M. Swanson, PhD

Arch Gen Psychiatry. 2007;64:932-940.

title: Depressed Dopamine Activity in Caudate and Preliminary Evidence of Limbic Involvement in Adults With ADHD

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