Exposure to heavy metals is associated with higher likelihood of ADHD diagnosis

A study in Spain found that children with higher levels of lead, cadmium, copper, and antimony in their urine had increased odds of being diagnosed with attention-deficit/hyperactivity disorder (ADHD). More specifically, higher levels of copper and cadmium were associated with more severe inattention symptoms, while higher levels of copper and antimony were linked to greater hyperactivity-impulsivity severity. The paper was published in the Journal of Attention Disorders.

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental condition marked by persistent inattention, hyperactivity, and impulsivity that interfere with daily functioning. It typically begins in childhood and can continue into adulthood, adversely affecting academic, occupational, and social life.

Globally, about 8% of children and 2.6% of adults are estimated to have ADHD. Boys are more frequently diagnosed than girls. In the United States, the diagnosis rate among children has risen steadily in recent decades, reaching about 11.4% by 2022. This increase is thought to reflect greater awareness, improved screening, and broader diagnostic criteria rather than a true rise in prevalence. Many adults remain undiagnosed until later in life, especially women and individuals with predominantly inattentive symptoms. ADHD often co-occurs with other conditions such as anxiety, depression, and learning disabilities.

Study author Sharanpreet Kaur and her colleagues note that the causes of ADHD are still not fully understood and that there is a knowledge gap regarding the role heavy metals might play in the development of this disorder. They examined 15 different metals: lead (Pb), arsenic (As), mercury (Hg), cadmium (Cd), chromium (Cr), copper (Cu), cobalt (Co), antimony (Sb), zinc (Zn), selenium (Se), magnesium (Mg), vanadium (V), manganese (Mn), nickel (Ni), and molybdenum (Mo).

Study participants were 190 children between 6 and 15 years of age, residing in the Spanish provinces of Barcelona and Tarragona. Their parents provided early-morning, fasting urine samples for the study. Among the children, 124 were diagnosed with ADHD, while 66 were not. Of the total sample, 131 were boys.

The researchers analyzed the urine samples for concentrations of the 15 listed metals.

Results showed that children with the highest levels of lead, cadmium, copper, and antimony in their urine were more likely to be diagnosed with ADHD. Additionally, higher copper and cadmium levels were associated with more severe inattention symptoms, while higher copper and antimony levels were linked to greater hyperactivity-impulsivity symptoms.

“This exploratory study provides preliminary valuable evidence, suggesting potential associations between environmental factors, such as metal exposure, with ADHD in school-aged children. These findings highlight the importance of further research to support these associations and, if confirmed, explore strategies to mitigate the potential impacts of these toxicants on children’s health,” the study authors concluded.

The study contributes to the scientific understanding of the environmental factors associated with ADHD. However, it should be noted that the design of the study does not allow any definitive causal inferences to be derived from the results.

The paper, “Investigating the Association Between Heavy Metals and Attention Deficit Hyperactivity Disorder in Children: An Exploratory Study,” was authored by Sharanpreet Kaur, Josefa Canals-Sans, Paula Morales-Hidalgo, José A. Alda, and Victoria Arija.