A URV research team reveals that the prevalence of attention deficit hyperactivity disorder (ADHD) is sixteen times higher in children with higher levels of copper in their bodies

Impulsivity, hyperactivity and difficulty concentrating are some of the symptoms associated with attention deficit hyperactivity disorder. It is estimated that 6% of schoolchildren in Catalonia suffer to a greater or lesser extent from this neurodevelopmental condition. Although genetic factors are the main cause, environmental factors such as exposure to pollutants can increase the risk of developing ADHD or can intensify its symptoms. “These factors influence brain development during pregnancy and the early years of a child’s life,” warned Fina Canals, a researcher with the URV’s Nutrition and Mental Health research group, which has investigated how exposure to metals affects neuropsychological performance and has linked it to the presence of ADHD during childhood.

“These elements accumulate in specific areas of the brain, such as the hippocampus or the frontal cortex, which are closely related to functions affected by ADHD,” explained Canals. The aim of their study was to determine whether there is a relationship between the presence in the body of heavy metals (which are suspected of aggravating the symptoms of ADHD) and the prevalence of this disorder in children aged between 6 and 16 years old.

To do this, they gathered data from 205 children: 139 who had been diagnosed with ADHD by the researchers themselves and a control group of 66 children without any associated neurodevelopmental disorders. Each child, accompanied by their families or legal guardians, was diagnosed individually by the researchers in accordance with the international DSM5 criteria. In addition to the diagnosis, the researchers also recorded IQ scores and indices of verbal comprehension, logical reasoning, working memory and visuomotor processing speed, among others. The presence of heavy metals in the body was analysed through urine samples in a specialised laboratory at the University of Granada, which focuses on levels of copper, cadmium, lead, arsenic, mercury and antimony.

More heavy metals, more ADHD

The researchers found that ADHD was up to five times more prevalent in those children in the sample who had the highest levels of lead in their bodies. In the case of copper, the relationship was even stronger, with children with the highest levels being sixteen times more likely to be diagnosed with ADHD. To a lesser extent, the team also linked cadmium and antimony levels to the presence of this neurodevelopmental disorder.

Copper, despite being an essential metal for healthy development, can be harmful in excessive amounts. In addition to finding a direct association between copper and ADHD, the research team also found a link between it and a worsening of symptoms such as inattention and impulsivity. Along with lead—recognised as toxic even at very low levels—copper has been linked to slower cognitive processing speed, an effect that is more pronounced in children with ADHD than in those without the diagnosis.

The results also link mercury exposure to increased inattention, frequency of omitted responses, and inconsistency in reaction times during cognitive testing. In particular it was noted that children already diagnosed with ADHD were more vulnerable and showed more intense negative effects even at the same levels of exposure, which suggests that they had greater sensitivity to environmental toxins.

“Although the study does not prove that heavy metals directly cause ADHD, its results reinforce the evidence that reducing exposure to these elements would promote healthy brain development,” argues Sharanpreet Kaur, co-author of the research and researcher at the URV’s Department of Psychology. On the basis of these results, such a reduction would also improve children’s learning experience and behaviour, especially in the most vulnerable cases.

The research team from the Nutrition and Mental Health research group collaborated with the CRAMC (Centre for Research in Assessment and Measurement of Behaviour) and plans to continue studying environmental factors that might increase the risk of ADHD or aggravate its symptoms. They are currently engaged in research on air pollutants. Given that the use of these metals is common and they may be present in contaminated soil, water, air and food, the researchers stress the need to strengthen public health measures, especially in terms of environmental monitoring, reduction of industrial emissions, safe waste management and food safety.

References: Kaur, S., Canals-Sans, J., Morales-Hidalgo, P., Alda, J. A., & Arija, V. (2025). Investigating the Association Between Heavy Metals and Attention Deficit Hyperactivity Disorder in Children: An Exploratory Study. Journal of Attention Disorders, 29(6), 423-436. https://doi.org/10.1177/10870547251315276 (Original work published 2025)

Kaur, S., Canals-Sans, J., Morales-Hidalgo, P. et al. Exposure to heavy metals and neuropsychological performance in children with and without attention deficit hyperactivity disorder (ADHD). Sci Rep 15, 40070 (2025). https://doi.org/10.1038/s41598-025-24319-7