London: Taking common painkillers during pregnancy more often is likely to raise the risk of autism and attention-deficit hyperactivity disorder (ADHD) in children, especially boys, new research warns. The findings also showed that pre-natal exposure to paracetamol raises the risk of autism spectrum diseases more in boys. "The male brain may be more vulnerable to harmful influences during early life. Our differing gender results suggest that androgenic endocrine disruption, to which male brains could be more sensitive, may explain the association," lead author Claudia Avella-Garcia, researcher at Centre for Research in Environmental Epidemiology (CREAL), a Spanish research organisation. On the other hand, maternal intake of paracetamol increased the risk of ADHD in children of both genders. Persistently exposed children in particular showed poorer performance in attention, impulsivity and visual speed processing. "An increase in the number of symptoms that a child has, can affect him or her, even if they are not severe enough to warrant a clinical diagnosis of a neurodevelopmental disorder," Avella-Garcia added. The exposed children were at higher risk of hyperactivity or impulsivity symptoms at age five. For the study, published in the International Journal of Epidemiology, the team recruited 2,644 mother-child pairs in a birth cohort study during pregnancy. Paracetamol could be harmful to neurodevelopment for several reasons. First of all, it relieves pain by acting on cannabinoid receptors in the brain. Since these receptors normally help determine how neurons mature and connect with one another, paracetamol could alter these important processes, the researchers explained. "It can also affect the development of the immune system, or be directly toxic to some foetuses that may not have the same capacity as an adult to metabolise this drug, or by creating oxidative stress," noted Jordi Julvez, one of the researchers from CREAL.