Association of Age and Response to Methylphenidate HCL Treatment in Adult ADHD: A Proton Magnetic Resonance Spectroscopy Study

Abstract

Purpose: This study investigated the age-dependent effects of methylphenidate (MPH) on brain metabolites including choline (Cho), N-acetyl aspartate (NAA) and creatine (Cr) levels in the dorsolateral prefrontal cortex (DLPFC), striatum, cerebellum, and anterior cingulate cortex (ACC) regions of the brain in adult patients with attention deficit hyperactivity disorder (ADHD). Patients and Methods: The study was included 60 patients with ADHD between the ages of 18 and 60 years. The patients were grouped with respect to their ages as follows: 18-24 years, 25-30 years, and 31 and over years. Levels of NAA, Cr and Cho in DLPFC, ACC, cerebellum and striatum were measured with magnetic resonance spectroscopy (MRS). Subjects were then given 10 mg of oral MPH and the same metabolite levels were measured 30 minutes apart. Results: Twelve (20%) of the cases were female and 48 (80%) were male. The age distribution of the cases is as follows: 15 subjects between the ages of 18-24, 26 subjects between the ages of 25-30 and 19 subjects over the age of 30. NAA levels were higher after MPH in the DLPFC of the 18-24 age group (p = 0.016) and in the cerebellum of the 25-30 age group (p = 0.041). No increase in Cho and Cr levels was observed after treatment compared to before (p > 0.05). Conclusion: It is thought that treatment of MPH can be effective on metabolites in different brain regions and this effect can vary upon age adult ADHD patients. After MPH treatment, both the 18-24 age group (in the DLPFC) and the 25-30 age group (in the cerebellum) was detected significantly higher NAA levels compared to pre-treatment levels. This increase in NAA levels suggested that pharmacotherapy, especially at early ages, may be effective on neuronal damage.