Dopamine transporter imaging in adult patients with attention-deficit/hyperactivity disorder

The aim of this study was to provide in vivo evidence for the hypothesis that dopaminergic neurotransmission is altered in adult patients with attention-deficit/hyperactivity disorder (ADHD). We used high-resolution brain-dedicated single-photon emission computed tomography and the dopamine transporter (DAT) marker [¹²³I]FP-CIT in 17 adult treatment-naïve ADHD patients and 14 age-matched controls. Magnetic resonance imaging-based region of interest analysis was performed to quantify the DAT availability (expressed as a ratio of specific to non-displaceable binding, V₃″) in the striatum. Additionally, the specific radiotracer binding was assessed in the thalamus and the midbrain/brainstem regions (reflecting also the availability of the serotonin transporter to which [¹²³I]FP-CIT binds with moderate affinity). In the striatal areas of the ADHD patients, a significantly reduced specific tracer binding was found (V₃″: 5.18 ± 0.98; controls 6.36 ± 1.34). In contrast, the specific [¹²³I]FP-CIT binding did not differ from controls in the thalamus and midbrain/brainstem areas. These data indicate a reduced dopaminergic but not serotonergic transmitter reuptake function in adult ADHD. Further studies will have to deal with the question of whether these findings have the potential to influence treatment decisions in this complex disorder.