The Role of Lead, Manganese, and Zinc in Autism Spectrum Disorders (ASDs) and Attention-Deficient Hyperactivity Disorder (ADHD): a Case-Control Study on Syrian Children Affected by the Syrian Crisis

Autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD) are two developmental disorders that affect children worldwide, and are linked to both genetic and environmental factors. This study aims to investigate the levels of lead, manganese, and zinc in each of ASD, ADHD, and ASD with comorbid ADHD in Syrian children born or grown during the Syrian crisis. Lead and manganese were measured in the whole blood, and zinc was measured in the serum in 31 children with ASD, 29 children with ADHD, and 11 children with ASD with comorbid ADHD (ASD-C) compared with 30 healthy children, their ages ranged between 3 and 12 years. Blood lead levels were higher in the groups of ASD-C (245.42%), ASD (47.57%), and ADHD (14.19%) compared with control. Lead levels were significantly higher in children with ASD in the age of 5 or less compared with control, and they were also higher in the male ASD compared with females (P = 0.001). Blood manganese levels were lower in the groups of ASD-C (10.35%), ADHD (9.95%, P = 0.026), and ASD (9.64%, P = 0.046). However, serum zinc levels were within the reference range in all groups of study. Lead and manganese were positively correlated with each other (P = 0.01). Lead increase and manganese decrease may associate with the incidence of ASD, ADHD, or the co-occurrence of both of them together. Further studies are needed to examine the relationship between metal levels and the co-occurrence of ASD and ADHD together.