Can Parents' Smoking Cause Childhood Behavior Problems?
What unknown power governs men? On what feeble causes do their destinies hinge!
The question first popped into my mind as I sat in a bar in rural England with four parents of severely hyperactive ADD children. As the parents each lit their cigarettes, they proceeded to tell me absolute horror stories about how their children had kicked in doors, smashed windows, punched and even stabbed their siblings, and violently attacked their parents and their teachers. These kids were out of control with a ferocity I'd rarely seen among middle-class ADD/ADHD children in the United States.
Why would this be? I wondered. Why did it seem that there was so much more violent childhood behavior among the children of England's middle class, as compared with America's?
Sometimes we don't notice what's right in front of us because we're so used to it. I'd heard similar stories from parents all over the UK, in Germany, and, particularly in poorer neighborhoods and on Indian reservations, in the United States.
As my lungs screamed in pain from all the cigarette smoke around me, my mind raced back over the many stories and the parents who'd told them to me. I looked at the smoke in the air, and recalled how many other times parents had sat with a cigarette in their hand and told me about their off-the-wall children.
Could it be?
How many, I wondered, of those parents of the "most violent" children were smokers? My mind began to race through the list. By my recollection, it seemed as if it were a majority, but then memory is often a highly variable thing. Maybe it was just the pain cigarette smoke causes me that was coloring my perceptions.
But the question persisted: Could there be a relationship between parental smoking and childhood violence?
And, if so, what was the mechanism? Was it that parents who smoke are more likely to come from lower socioeconomic classes, where hitting a child as a form of discipline is more accepted? Or could it be that the children had become addicted to the nicotine in the passive smoke and were acting out a craving or withdrawal when they didn't have it?
Sitting in that pub, these questions raced through my mind. I was beginning to feel restless, my nose and lungs on fire, my heart racing as I inhaled their heart-stimulating drug.
At that time, I knew that nicotine is the most addictive drug currently known to man. It's more addictive than heroin (by one measure it's five times more addictive), more addictive than crack cocaine, and far more addictive than alcohol (as you can see from all the smokers at any AA meeting). Inhaling nicotine in smoke causes it to hit the bloodstream and the brain twice as fast as injecting it, so smokers get a more rapid "rush" than heroin users (which is why they're often so resistant to using nicotine gum, which eliminates the craving but doesn't give the "high" because it hits the bloodstream hundreds of times more slowly).
I also knew that nicotine is one of the most powerful drugs we know of to affect the central nervous system (CNS). It's wildly more powerful than amphetamine or Ritalin, for example.
It's such a powerful CNS drug that the tobacco plant produces it as an insecticide to kill predatory bugs. Nicotine is purified from tobacco and used as an insecticide in some countries and it's incredibly effective, leaving virtually any insect in its path twitching and convulsing in massive CNS overload. The main reason it's not more widely used on crops, in fact, is because it's so dangerous to humans: three drops of pure nicotine on the skin will kill a full-grown man in less than ten minutes.
Wondering if there may be a connection between childhood behavior and parental smoking, I did a bit of research.
The first article I found was in the July 15, 1992 issue of the American Journal of Medicine ("Nicotine and the central nervous system: biobehavioral effects of cigarette smoking"). In it, researchers pointed out that nicotine is a "neuroregulatory" drug, which profoundly adjusts and modifies the state of the entire central nervous system. When nicotine is absorbed (by smoking or inhaling others' smoke), "dose-dependent neurotransmitter and neuroendocrine effects occur," including increases in blood levels of norepinephrine and epinephrine (two hormone/neurotransmitters involved in the "fight-or-flight" response), and brain levels of dopamine (one of the neurotransmitters some researchers think is off-balance in children with ADD) are altered. Other hormones and neurotransmitters that flood the brain as a result of exposure to nicotine include arginine, vasopressin, Beta-endorphin, adrenocorticotropic hormone, and cortisol (the violence-enhancing hormone released when a person is under stress). Several of these neurochemicals are so highly psychoactive that they modify behavior at a "limbic brain level" in a way which is beyond the conscious control of the individual <%10>...<%0> as any smoker who's tried to quit will tell you.
This was an interesting beginning, but I narrowed the search to specifically look for a correlation between "bad behavior" (not just ADD but disruptive or violent behaviors) and parental smoking.
What I found then was shocking.
It began in 1979, when a national survey was done by Harvard Medical School and the University of Rochester, polling 12,000 young people between the ages of 14 and 22 to determine their smoking and childbearing behaviors. Follow-up interviews were conducted annually, and by 1986 it was found that 2256 children, ranging in age from 4 years to 11 years old, had been produced by this group. At that point, the children of these parents were rated as to their behaviors, and it was found that children of smokers were "40-50% more likely" to be extremely disruptive than children born of or living in the homes of nonsmokers. Researcher Barry Zuckerman published the results of this multi-year, large-population study in the September, 1992 edition of the well-known Child Health Alert publication for physicians.
Interestingly, Zuckerman's epidemiological data found that smoking during pregnancy wasn't nearly as likely to cause "extreme" behaviors among children as was smoking in the house where the children were living. Passive smoke, according to this study, was a clear candidate for the role of "cause" for the extreme behaviors of many of these children.
Another report discussing this study, published in the Pediatric Report's Child Health Newsletter in 1992, pointed out that the researchers had been so meticulous as to even determine that there was a "dose dependent" correlation between how much nicotine the children inhaled in the home environment and how severe their behavior was. They pointed out that children of mothers who smoked more than a pack of cigarettes a day were twice as likely (that's 100% more likely!) as other mothers to have children with highly disturbed behavior, whereas mothers who smoked less than a pack a day were only 1.4 times as likely to produce these types of children.
At first, reading this, I wondered if it might just be that people who smoke generally (particularly in the USA) are more likely to come from lower income groups. In the upper-middle-class suburbs of Atlanta where I've lived for the past decade, I don't know of a single parent who smokes: it's seen as a sign of low class. In England and the rest of Europe, however, that distinction has not yet hit the masses, and smoking is widely accepted. And in England I also found many, many more highly disruptive children than I've found in America among the children of people showing up for ADD support groups. So I wondered, could it be a class or income issue?
"No," was the unequivocal answer of this study's authors. They'd carefully factored out issues of class, income, lifestyle, use of other drugs, and even diet from their study. This was smoking around the kids, and only smoking around the kids, that predicted violent and disruptive behavior.
Since that time, I was amazed to discover, numerous studies have been done which corroborated the conclusions of this early Harvard study. One was published in the prestigious medical journal Pediatrics in 1992. In that study, Weitzman and his colleagues found a clear correlation between how much Mom smoked and how off-the-wall (my term, not theirs) her child was. They wrote that the connection was "highly statistically significant," which is researcher jargon for "This looks like a very strong connection!!"
That study's publication was followed by the publication of another, a year later and also in Pediatrics, this time by David Fergusson and two other scientists. They spent twelve years studying children of mothers in New Zealand who smoked, compared to a carefully selected group of similar class/income/lifestyle nonsmokers. In this study of 1,265 children, they methodically removed from consideration other possible causes of (or variables affecting) poor conduct, including gender, ethnicity, family size, maternal age, maternal education, socioeconomic status, standard of living, maternal emotional responsiveness, avoidance of punishment, number of schools attended, life events, changes of parents, parental discord, parental history of drug use, and parental history of criminal offense.
Having pulled out every possible factor which could contribute to a child becoming violent, acting out, or engaging in antisocial behavior, only one factor was left, and it was staring them right in the face. Their research found a clear and obvious association between mothers smoking during pregnancy and both "poor conduct" and "attention deficit disorders" (their phrase).
Other studies have corroborated these. They include studies done by Fried & Watkinson (Neurotoxicology & Teratology, 1988), McCartney ("Central auditory processing in school-age children prenatally exposed to cigarette smoke," Neurotoxicology & Teratology, 1994), Richardson and Tizabi ("Hyperactivity in the offspring of nicotine-treated rats: Role of the mesolimbic and nigostriatal dopaminergic pathways," Pharmacology and Biochemistry of Behavior, 1994), Sexton & Fox ("Prenatal exposure to tobacco: Ill effects on cognitive functioning at age three," International Journal of Epidemiology, 1990), Wakschlag & Lahey, et al ("Maternal smoking during pregnancy associated with increased risk for conduct disorder in male offspring," manuscript submitted for publication), Weitzman & Gortmaker, et al ("Maternal smoking and behavior problems of children," Pediatrics, 1992), Bertolini & Bernardi ("Effects of prenatal exposure to cigarette smoke and nicotine on pregnancy, offspring development, and avoidance behavior in rats," Neurobehavorial Toxicology, 1982), Cotton ("Smoking cigarettes may do developing fetuses more harm than ingesting cocaine," Journal of the American Medical Association, 1994), and Fried & Gray ("A follow-up study of attentional behavior in 6-year-old children exposed prenatally to cigarettes¼" Neurotoxicology & Teratology, 1992).
These studies not only corroborated the earlier ones, but also showed that this effect could be seen in rats and other animals (which rules out the socioeconomic factors theory). In rats and dogs, researchers have found that "passive" exposure to smoke "alters neurotransmitter functioning" (Cotton, 1994; Slotkin, 1992), increases hyperactivity and motor activity (Richardson & Tizabi, 1994), and decreases learning efficiency and ability (Bertolini, et al., 1982). In humans, they showed that nicotine exposure could do profound damage to the cognitive (thinking) abilities of children from birth right through the teenage years, and that the longer and more severe the exposure was, the more visible and serious was the damage. Several of these studies focused specifically on conduct disorders, and the results were consistent: exposure to "passive" cigarette smoke in the home correlates with violent behavior in children.
The mechanism by which this effect takes place is, at this moment, unknown. It is known, however, that cigarette smoke stimulates at least two different parts of the brain at the same time. It stimulates the production of cortisol, the "stress hormone," which leads to large releases of adrenaline, epinephrine, and other "rage" and "fight-or-flight" hormones and neurotransmitters, and, in the high doses that a smoker inhales, also stimulates the production of endorphins, the naturally-occurring opiates of the brain which produce the "high" smokers experience (along with the cortisol stimulation).
But while smokers are getting both parts of their brain stimulated, children inhaling their smoke are only getting enough nicotine to stimulate the cortisol mechanism: the dose isn't high enough to produce endorphins.
This is intuitive knowledge to any smoker - ask him how he'd feel if he could only smoke one or two cigarettes a day, instead of the twenty or forty he normally smokes. He'll describe how easily upset, on-edge, irritable, and filled with anxiety he'd feel at such a low dose of nicotine - which is the sort of dose his children are receiving as second-hand smoke.
Reading these studies, and many others that I came across in the course of my research, I was amazed that the issue of cigarette smoking around children hadn't gotten more coverage in the popular media. Certainly if a child were exposed to, for example, marijuana smoke at home, there would be considerable concern among the authorities about the child's absorption of THC, the active drug in that plant. And the same would be true of parents who smoked crack cocaine. But nicotine?
Then I remembered my days working as a writer and contributing editor to numerous magazines. Nearly all took hundreds of thousands, sometimes millions, of dollars a year from the tobacco companies in exchange for advertising. Who would bite that hand?
Only medical journals like Pediatrics, which don't carry advertisements for cigarettes...
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