Tabacco And Lead Linked to ADHD

The study estimated that up to 35 per cent of cases (around 800,000 children in the US population) of ADHD in youngsters aged between 8 and 15 could be reduced by getting rid of both prenatal exposure to tobacco and childhood exposure to lead.

The Research

The research used data on 2,588 youngsters aged 8 to 15 who had taken part between 2001 and 2004 in the National Health and Nutrition Examination Survey (NHANES).  NHANES is a cross-sectional, nationally representative sample of the population of the US and includes information about health and diet. 

To assess prenatal exposure to tobacco, the researchers used mothers’ reports on cigarette use during pregnancy. To assess lead exposure, the researchers used current blood lead levels, and the diagnosis for ADHD was based on the Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition, considered the "gold standard" for defining certain mental health conditions.

The Results

The results showed that:

• 8.7 per cent of the children met the diagnostic criteria for ADHD
• Children exposed prenatally to tobacco smoke were 2.4 times more likely to have ADHD
• Children whose blood levels were in the top third (upper tertile) for lead were 2.3 times more likely to have ADHD
• Children with both prenatal tobacco exposure and in the top third for blood lead levels were 8.1 times more likely to have ADHD compared to children with neither exposures
• The increased risk of ADHD from both types of exposure was even greater than expected by multiplying the independent risks

Comments

Lead author Dr Tanya Froehlich, a physician in the Division of Developmental and Behavioral Pediatrics at Cincinnati Children’s said:  "Tobacco and lead exposure each have their own important adverse effect."  "But if children are exposed to both lead and prenatal tobacco, the combined effect is synergistic," she explained.  It is especially among those with both exposures.