Second-hand Smoke Exposure Linked to Psychological Problems in Children

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The first evidence linking mothers’ second-hand smoke exposure while pregnant to their child’s attention deficit disorder (ADHD) and conduct disorder has been published in the current issue of Child Psychiatry and Human Development. ADHD and conduct disorder behaviors are called externalizing psychopathology with symtoms that include aggressive behavior, ADHD, defiance and conduct disorder.

The study compared patterns of psychopathology among three groups of children aged 7 to 15 years, all of whom had significant behavioral and/or emotional problems. Children in group 1 did not experience prenatal smoke exposure. Group 2 mothers smoked during the last two trimsters of pregnancy. Group 3 mothers were only exposed to second-hand smoke at home or at work in the final two trimesters of pregnancy. In total, 171 children (primarily boys) and 133 women participated in the study.

Researchers found that children whose mothers had been exposed to tobacco smoke either by smoking or exposure to second-hand smoke when they were pregnant had more symptoms of ADHD and conduct disorder than children whose mothers did not experience smoke exposure. The children whose mothers had been exposed to tobacco smoke did not show more symptoms of emotional disorders (e.g. depression, anxiety). Researchers controlled for a number of factors including family income, parents’ substance abuse, birth weight and parents’ anti-social behavior. However, second-hand smoke exposure remained the primary predictor of ADHD and conduct disorder.

Nicotine

Nicotine is an alkaloid compound (meaning a nitrogen-containing ring compound produced by a plant, usually water-insoluble and alcohol soluble) in tobacco and is believed to be the cause of these behavior problems in children. Here’s why: the changes observed in receptor-mediated cell signaling in the brain and heart of rats treated with nicotine during pre- or postnatal development mimics those caused by environmental tobacco smoke exposure [1]. Nicotine in tobacco smoke interferes with fetal neurodevelopment, specifically the developing nervous system. In animal models in utero, nicotine alters the pattern of cell proliferation and differentiation by targeting nicotinic acetylcholine receptors in the fetal brain. Cell numbers are reduced and the resulting effect is altered synaptic activity [2]. The changes occur in areas of the brain critical to the development of externalizing psychopathology in humans.

On a side note, a study published earlier this year links prenatal exposure to tobacco smoke with changes in brain physiology associated with basic perceptual skills and affects speech-processing ability in newborn infants [3]. Further work suggests that prenatal and adolescent exposure to nicotine exerts gender-specific effects that are detrimental to auditory and visual attention, along with accompanying changes in the efficiency of neurocircuitry supporting auditory attention [4].

The adverse effects of nicotine involve multiple cellular signaling pathways and affect both immediate developmental fetal brain events and the eventual programming of synaptic competence. Thus, affective and behavioral defects may appear in childhood or adolescence after a period of apparent normality.

The statistics

In the U.S. in 2005, an estimated 60.5 million Americans (24.9% of the population) were current cigarette users. In the 1990s, despite the overwhelming data on adverse health effects, smoking prevalence increased sharply among teenaged girls and until recently, a higher percentage of girls than boys aged 12 to 17 used cigarettes within the past month [5].

Unfortunately, the most recent data available indicates that 22.3% of women 15 to 17 years of age and 26.4% of women 18 to 25 years of age are pregnant and smoke [5]. In addition to the irreparable damage to their unborn children discussed above, women who smoke have an increased risk for developing cancers of the mouth, pharynx, larynx, esophagus, pancreas, kidney, bladder and uterine cervix [6].

What you can do

According to the Surgeon General, there is no risk-free level of exposure to second-hand smoke. Opening a window, sitting in a separate area or using ventilation, air conditioning or a fan cannot eliminate second-hand smoke exposure. Here are some tips to protect yourself and your loved ones:

1. Stop smoking. Get help if you need it, but stop smoking today.
2. Don’t smoke if you’re pregnant. Avoid second-hand smoke exposure.
3. Don’t allow smoking in your home or your car.
4. Ensure that your child’s schools and care facilities are smoke free.
5. Insist on smoke-free sections in restaurants and other public places. Patronize those establishments that are smoke-free.
6. Don’t allow smoking around your children. If someone insists on smoking around your children, leave. Don’t risk your child’s health.
7. Take an active interest in your child’s social life. Ask if your child’s friends smoke. Be aware of who your child hangs out with and if they smoke. Teach your child about the dangers of smoking and why they don’t want to be exposed to it.

References

1. Slotkin et al. Perinatal exposure to environmental tobacco smoke induces adenylyl cyclase and alters receptor-mediated cell signaling in brain and heart of neonatal rats. Brain Res. 2001 Apr 13;898(1):73-81. DOI: 10.1016/S0006-8993(01)02145-X
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2. Slotkin TA. Fetal nicotine or cocaine exposure: Which one is worse? J Pharmacol Exp Ther. 1998; 285:931-945
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3. Key et al. Smoking during pregnancy affects speech-processing ability in newborn infants. Environ Health Perspect. 2007 Apr;115(4):623-9. Epub 2006 Nov 28.
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4. Jacobsen et al. Gender-Specific Effects of Prenatal and Adolescent Exposure to Tobacco Smoke on Auditory and Visual Attention. Neuropsychopharmacology. 2007 Mar 21; [Epub ahead of print].
   View abstract
5. 2005 National Survey on Drug Use & Health Results. U.S. Department of Health and Human Services. Substance Abuse and Mental Health Services Administration. Office of Applied Studies. 2005.
6. Women and Smoking: A Report of the Surgeon General, 2001. U.S. Department of Health and Human Services. 2001.