International Journal of Contemporary Pediatrics | March 2020 | Vol 7 | Issue 3 Page 640 International Journal of Contemporary Pediatrics Sehgal R et al. Int J Contemp Pediatr. 2020 Mar;7(3):640-646 http://www.ijpediatrics.com pISSN 2349-3283 | eISSN 2349-3291 Original Research Article Blood heavy metal levels in children with attention deficit hyperactivity disorder: an unsolved enigma Rachna Sehgal 1 , Sheffali Gulati 1 *, Yogendra K. Gupta 2 , Savita Sapra 1 , Ravindra M. Pandey 3 , Madhulika Kabra 1 INTRODUCTION Attention deficit hyperactivity disorder (ADHD) is a neurobehavioral disorder that is believed to result from an interplay of environmental influences with inheritable factors. Amongst environmental factors, the possible contribution of heavy metals seems logical as cellular enzyme systems are disrupted by heavy metals and there is environmental ubiquity of various heavy metals. However, in the currently available literature, there are discordant results of association of heavy metals especially lead with ADHD. Moreover, studies with discordant results are from different geographical localities with different environments, monitoring and regulations and socioeconomic backgrounds. ABSTRACT Background: The role of heavy metals in the etio-pathogenesis of attention deficit hyperactivity disorder (ADHD) is a burning enigma. The available studies with discordant results are from different geographical localities with different monitoring, regulations and sociocultural backgrounds. The differential association of heavy metals with ADHD severity and phenotypes has not been adequately examined. Also, there are concerns about laboratory quality control. Therefore, the present case control study was formulated. Methods: Thirty children with ADHD diagnosed by DSM IV criteria and thirty group age matched controls were enrolled. Detailed perinatal, past, developmental and possible exposure history to various heavy metals was taken. Severity of ADHD was assessed using Conners TM Parent reporting questionnaire. Blood level of metals was estimated by inductively coupled plasma- atomic emission spectroscopy (ICP-AES). Results: The mean blood lead, mercury, cadmium, arsenic, zinc were comparable in children with ADHD and group age matched controls. The mean blood lead, mercury and cadmium levels in study population was higher than found in studies from developed countries. Elevated arsenic, mercury and cadmium were found in both cases and controls. Blood zinc correlated significantly with inattention T score and blood mercury with hyperactivity-impulsitivity T score of Conners parent rating scale. Blood cadmium was present in greater proportion of predominant hyperactive- impulsive type patients. Conclusions: Zinc deficiency correlates with inattention; cadmium and mercury toxicity correlate with hyperactivity. Mean blood levels of heavy metals is elevated in a substantial proportion of study population. So, there is an urgent need for sensitization and environmental control. Keywords: Attention deficit hyperactivity disorder, Cadmium, Lead, Mercury, Zinc 1 Department of Pediatrics, 2 Department of Pharmacology, 3 Department of Biostatistics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India Received: 12 December 2019 Revised: 23 January 2020 Accepted: 28 January 2020 *Correspondence: Dr. Sheffali Gulati, E-mail: sheffaligulati@gmail.com Copyright: © the author(s), publisher and licensee Medip Academy. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. DOI: http://dx.doi.org/10.18203/2349-3291.ijcp20200693