Objective: Attention deficit-hyperactivity disorder (ADHD) is an important psychiatric illness with a prevalence of 5% worldwide, which is characterized by core symptoms like hyperactivity, attention deficit and impulsivity and it effects on the patients’ and their families’ quality of life. Even though the pathogenesis of ADHD is still greatly unknown, evidences from different researches point out primarily the dopaminergic and noradrenergic (NA) system. In this study, it was aimed to be compared plasma dopamine (DA) and NA levels in children diagnosed with ADHD in baseline and after two months methylphenidate OROS treatment.
Method: 50 children with the diagnosis of ADHD within the age range of 6-12 years were recruited in the study. The psychiatric diagnoses were determined by applying a semi-structured interview with Kiddies Schedule for Affective Disorders and Schizophrenia for School Aged Children- Present and Lifetime Version (K-SADS-PL). The symptom severity of ADHD was measured by Clinical Global Impression (CGI) ADHD severity scale. Clinicians filled up Du Paul ADHD scale. Plasma DA and NA levels were measured before methylphenidate treatment and two months after beginning methylphenidate OROS.
Results: According to a paired samples T-test, mean plasma DA levels in the baseline were 169.27 and 180.82 in the end point, (t=-1.339, df=49, p=0.187) and baseline NA level was 232.03 and after methylphenidate OROS treatment it was 232.03 (t=1470, df=49, p=0.148). There were no significant changes for both DA and NA levels between pretreatment and post-treatment significant difference was not found between three subtypes of ADHD. The difference between DA and NA levels and comorbidity did not reach statistical significance and there was no correlation between DA and NA and Dupaul or CGI scores.
Conclusion: To our knowledge, this is the first study in which plasma DA and NA levels were measured pretreatment and two months after methylphenidate OROS treatment Catecholaminergic pathways have been implicated in the neurobiological causes responsible for the emergence of ADHD. A better understanding of the possible roles of catecholaminergic and non-catecholaminergic systems in ADHD could advance our understanding of the disorder and help determine better treatment regimens.