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.

Keywords:

• adult
• attention deficit hyperactivity disorder
• magnetic resonance spectroscopy
• methylphenidate
• age

Abbreviations

ADHD, attention deficit hyperactivity disorder; PFC, prefrontal cortex; MRS, Magnetic resonance spectroscopy; NAA, N-acetyl aspartate; Cr, creatine; Cho, Choline; MPH, Methylphenidate; DLPFC, dorsolateral prefrontal cortex; ACC, anterior cingulate cortex; DSM-IV, Diagnostic and Statistical Manual for Mental Disorders; WURS, Wender Utah Rating Scale.

Data Sharing Statement

The data associated with the paper are available from the corresponding author upon reasonable request.

Ethics Approval

The study was conducted in line with the principles of the Declaration of Helsinki and approved by the Ethics Committee of Faculty of Medicine, Pamukkale University (date:25/03/2011 approval number:52). All patients included in the study provided written informed consent.

Acknowledgments

We thank to Dr. Yilmaz Kiroglu, MSc, for their consultancy in radiology and Dr. Hande Senol, MD, for their consultancy in biostatistics.

Author Contributions

Gonca Ayse Unal and Ayse Nur Inci Kenar made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors declare that they have no conflicts of interest in this work.

Additional information

Funding

Funding was provided by the Commission of Scientific Research Project, Pamukkale University.