Secondhand Smoke Exposure Linked to Mental Disorders in Children A higher level of salivary cotinine, a biomarker used to measure secondhand smoke (SHS) exposure, is associated with poorer mental health particularly hyperactivity and conduct disorder in children, suggests a new community-based study drawn from the Scottish Health Surveys. In addition, investigators found that 40% of the more than 900 children included in the study had high SHS exposure, with the highest cotinine levels found in those living in poorer areas. "We know that secondhand smoke is linked to physical health outcomes in kids, but we know little about the mental health effects," lead study author Mark Hamer, PhD, associate professor of social epidemiology in the Department of Epidemiology and Public Health at University College London, United Kingdom, told Medscape Medical News. "Smoking parents should be educated [by clinicians] about the harmful effects of secondhand smoke exposure on their kids," said Dr. Hamer. The study was published online December 6 in the Archives of Pediatrics and Adolescent Medicine.