Second-Hand Smoke While Pregnant
The question about whether second-hand smoke causes ADHD has been addressed by some research. But some of that research stretches back to before the child with ADHD was even born. A University of Washington study published in a 2007 issue of Child Psychiatry and Human Development linked mothers' second-hand smoke exposure levels with ADHD and other disorders in the fetus. In other words, if a mother is exposed to second-hand smoke on a regular basis while pregnant, the child that comes from that pregnancy is at a higher risk of developing ADHD, as well as other conduct disorders (e.g., aggressive behavior, fighting, school failure, substance abuse).
The researchers studied three groups of children between the ages of seven and fifteen who had significant behavioral and/or emotional problems. Of the three groups, one had mothers who smoked during the last six months of pregnancy, one had mothers who were exposed to second-hand smoke during that same time period, and one had mothers who had no smoking exposure during pregnancy. One hundred and seventy one children took part in the project. The first two groups of children were found to have more ADHD and conduct disorder symptoms than those in the last group, even when controlled for family income, parents' drug abuse, postnatal weight, and parents' behavior.
Second-Hand Smoke and Young Children
In October of 2010, a US study found that children who have had exposure to second-hand smoke have much higher rates of ADHD. The study collected data about cigarette smoke exposure for children and adolescents between the ages of four and fifteen, as well as measuring their blood cotinine levels (levels of exposure to tobacco smoke). According to the results of the study, children with second-hand smoke exposure had a 10.6% chance of having ADHD. Children who had no exposure to second-hand smoke had about half of that chance, at 4.6%. Socioeconomic factors and prenatal exposure were controlled for in this study.
The Alleged Cause
So how can second-hand smoking cause ADHD? The culprit is said to be nicotine, the alkaloid compound found in tobacco. Even animal studies have shown the impact that nicotine can have on the development of the brain development during pregnancy; changing parts of the brain that are involved in the way that people react to the events around them. Especially when a fetus is exposed in uterine, the high levels of dopamine (a chemical that affects behavior and thinking), can be extremely susceptible to the nicotine in second-hand smoke.
One of the researchers involved in the University of Washington study believes that cigarette smoke exposure in utero can affect children even as infants and toddlers, before ADHD symptoms can be identified. He believes that as babies they are more likely to have colic and be hard to calm, and that as toddlers they are overly active and refuse to listen to authority more often than other toddlers.
This post is part of the series: Possible Causes of ADD and ADHD
Did you ever wonder what causes ADD and ADHD? There appear to be many factors that can affect these disabilities. These articles explore several factors that researchers are looking at currently.