Conflict of interest statement: No conflicts declared.
Confirmation and extension of association of blood lead with attention-deficit/hyperactivity disorder (ADHD) and ADHD symptom domains at population-typical exposure levels
Article first published online: 23 NOV 2009
© 2009 The Authors. Journal compilation © 2009 Association for Child and Adolescent Mental Health
Journal of Child Psychology and Psychiatry
Volume 51, Issue 1, pages 58–65, January 2010
How to Cite
Nigg, J. T., Nikolas, M., Mark Knottnerus, G., Cavanagh, K. and Friderici, K. (2010), Confirmation and extension of association of blood lead with attention-deficit/hyperactivity disorder (ADHD) and ADHD symptom domains at population-typical exposure levels. Journal of Child Psychology and Psychiatry, 51: 58–65. doi: 10.1111/j.1469-7610.2009.02135.x
- Issue published online: 9 DEC 2009
- Article first published online: 23 NOV 2009
- Manuscript accepted 8 April 2009
- blood lead
Background: Recent studies have suggested that child attention-deficit/hyperactivity disorder (ADHD) and its symptom domains are related to blood lead level, even at background exposure levels typical in western countries. However, recent studies disagreed as to whether lead was related to inattention or hyperactivity-impulsivity within the ADHD domain. More definitive evaluation of these questions was sought.
Methods: Two hundred and thirty-six (236) children aged 6–17 years participated (61 ADHD-Combined type, 47 ADHD Predominantly Inattentive type, 99 non-ADHD control, 29 unclassified borderline, situational, or not otherwise specified (NOS) cases). Formal diagnosis was reliably established by a best estimate procedure based on a semi-structured clinical interview and parent and teacher ratings. Lead was assayed from whole blood using inductively coupled plasma mass spectrometry with a method detection limit of .3 μg/dL.
Results: Blood lead levels were slightly below United States and Western Europe population exposure averages, with a mean of .73 and a maximum of 2.2 μg/dL. This is the lowest level of blood lead ever studied in relation to ADHD. After statistical control for covariates including IQ and prenatal smoking exposure, blood lead was associated with ADHD-combined type but not inattentive type. Parent and teacher report indicated association of blood lead with Conners cognitive problems, but only teacher report showed effects on DSM-IV inattention symptoms. Blood lead was associated with hyperactivity-impulsivity in parent report regardless of measurement method, whereas teacher report effects depended on child treatment history.
Conclusions: These findings confirm that in children with typical US population lead exposure, careful identification of children with ADHD also identifies children with slightly elevated blood lead.