Hair and urine lead, cadmium, nickel, and arsenic levels in children with attention-deficit hyperactivity disorder: A case-control study in a tertiary care hospital in eastern India

Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by inattention and/or hyperactivity-impulsivity. It is one of the most widespread neurodevelopmental conditions and has compound etiopathogenesis involving both environmental and genetic factors. Though the role of heavy metals on ADHD has been implicated but is less studied. Hair and urine are two non-invasive methods which can substitute blood as a method of monitoring and assessing heavy metal levels. Twenty-four cases of ADHD and their age matched healthy children (24) were taken as controls. Hair and urine samples were analyzed for lead, cadmium, nickel, and arsenic using inductively coupled plasma optical emission spectrometry (ICP-OES) after acid digestion and extraction. The levels of heavy metals were significantly higher in cases; lead (p = .004, .003), cadmium (p = .020, <.001), and nickel (p = .016, <.001) of the hair and urine samples, respectively. Arsenic was below the limit of detection for all the samples. Hence, in conclusion, the heavy metal levels in hair and urine were significantly higher in ADHD cases as compared to their healthy counterparts.