| Does Methylphenidate Cause a Cytogenetic Effect in Children with Attention Deficit Hyperactivity Disorder? Susanne Walitza,1 Birgit Werner,2 Marcel Romanos,1 Andreas Warnke,1 Manfred Gerlach,1 and Helga Stopper2 1Department of Child and Adolescent Psychiatry and Psychotherapy, and 2Department of Toxicology, University of Würzburg, Würzburg, Germany Abstract
Background and objective: Attention deficit hyperactivity disorder (ADHD) is the most common psychiatric disorder in children and adolescents (6–12% affected) . Treatment with methylphenidate (MPH) in the United States has increased to a current prescription rate of > 5 million per year. However, a 2005 study by El-Zein and co-workers [Cancer Lett 230:284–291]reporting a 3-fold increase in genomic damage in all 12 analyzed children after 3 months of therapy with MPH resulted in much concern about potential carcinogenic effects. Here we provide new information concerning the cytogenetic effect of MPH in children. Design, participants, and methods: In a prospective study, we analyzed the genomic damage in children with ADHD (initial sample size 38 children) before and 1 (30 children) , 3 (21 children) , and 6 (8 children) months after initiation of MPH therapy. In addition, we investigated a group of 9 children receiving chronic MPH therapy. Patients were recruited within a study of our Clinical Research Group on ADHD in the Department of Child and Adolescent Psychiatry and Psychotherapy of the University of Würzburg. Assessment and treatment of patients were performed during inpatient or outpatient health care. The measure for genomic damage was the frequency of micronuclei, a subset of chromosomal aberrations, in peripheral lymphocytes. Results: MPH treatment resulted in no significant alteration in the micronucleus frequency. Conclusions: Because the findings published in 2005 by El-Zein and co-workers could not be replicated, the concern regarding a potential increase in the risk of developing cancer later in life after long-term MPH treatment is not supported. Key words: ADHD, cytogenetic effects, methylphenidate, micronuclei, psychostimulants. Environ Health Perspect 115:936–940 (2007) . doi:10.1289/ehp.9866 available via http://dx.doi.org/ [Online 21 February 2007]
Address correspondence to H. Stopper, Department of Toxicology, University of Würzburg, Versbacher Strasse 9, D-97078 Würzburg, Germany. Telephone: +49 931 201 48427. Fax: +49 931 201 48446. E-mail: stopper@toxi.uni-wuerzburg.de We gratefully acknowledge the technical assistance of M. Kessler and A. Nowak. This study was partially funded by grants from the German Research Foundation (Deutsche Forschungsgemeinschaft ; KFO 125/1-1) and from the Interdisciplinary Center for Clinical Research [IZKF N-5 (1) ] and was performed independent of financial or other support by companies producing or selling methylphenidate. The authors declare they have no competing financial interests. Received 30 October 2006 ; accepted 21 February 2007.
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