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Abstract:
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The Attention-Deficit/Hyperactivity Disorder (ADHD) is a neuropsychological disorder characterized by inattention, impulsivity and/or hyperactivity. It is one of the most common disorders in childhood with an average prevalence of 5%. Symptoms persist into adulthood in 30-60% of the cases, with 3.4% of the adults maintaining a full-diagnose. Although it is a highly diagnosed disorder, its etiology is still unclear. Currently, the most widely accepted theory points to a dysfunction of the dopamine neurotransmission. ADHD patients present an alteration of the nucleus accumbens (NA). Therefore, this neurostructure is the key target of the pharmacological treatment, mainly Methylphenidate (MPH), which blocks dopamine active transporter (DAT) leading to an increase in dopamine. Despite being the most commonly used pharmacological treatment for ADHD, the neurobiological long-term effects of MPH are poorly understood. Moreover, there is a lack of neuroimaging studies addressing possible changes in brain structure due to pharmacological treatment, especially in adult populations. Therefore, the aim of this study was to apply a ROI analysis to structural magnetic resonance imaging scans to examine whether there were volumetric differences in the nucleus accumbens (NA). The study compared a group of ADHD subjects (n=34) with a group of control subjects (n=33). Addtionally, we studied the NA differences between the sub-group of MPH medicated subjects (n=7) with the sub-group of medication-naïve subjects (n=26). The ADHD group presented a larger NA compared to control group and medicated patients presented a smaller NA compared to non-medicated patients, but none of these differences were statistically significant. It is important to perform more studies with larger and homogeneous samples in order to draw firm conclusions. |
