Smoking in adolescence contributes to attention problems that persist into adulthood, a new study of identical twins suggests.
"Since our results imply that smoking causally increases attention problems, the most important implication of this study is that the initiation of smoking should be prevented or delayed as much as possible," Jorien Treur, doctoral candidate, Department of Biological Psychology, VU University Amsterdam, the Netherlands, told Medscape Medical News.
"The prevention of smoking is even more important for adolescents who already have attention problems (eg, ADHD). We know from previous studies that these adolescents are more likely to start smoking, but now our study has shown that smoking could also further increase their preexisting attention problems," she added.
The study was published in the November 1 issue of Biological Psychiatry.
The researchers used the "powerful" discordant monozygotic co-twin design to test whether smoking leads to attention problems, Treur explained.
"Monozygotic twins share approximately 100% of their DNA, and a large part of their [family] environment. If these twin pairs who are discordant for smoking differ in attention problems, it can't be due to genetic or shared environmental factors (because these are shared by the twins)," she said.
The researchers had longitudinal data on smoking and attention problems for 1987 adult and 648 adolescent monozygotic twin pairs from the Netherlands Twin Register.
They found that adult twins who had ever smoked had significantly more attention problems than their never-smoking co-twins.
Among adolescent twin pairs discordant for smoking, greater attentional problems were found at age 16 years in the individuals who smoked compared with their co-twins who did not. "This difference in attention problems did not yet exist when the twins were younger and neither smoked. The effect also remained after correcting for the twins' educational level, alcohol use, and cannabis use," Treur said.
The finding that individuals who smoked had more attention problems than their nonsmoking twins suggests a causal effect of smoking, the researchers say. It also provides further support for the "hypothesis that smoking affects the brain and increases attention problems, as suggested in animal studies," the authors write.
In an accompanying editorial, Edythe D. London, PhD, from the Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine, at the University of California, Los Angeles, says the findings do "support the conclusion that smoking in adolescence produces problems with attention that persist to adulthood." They provide "strong evidence that exposure to nicotine, in combination with the many other components of tobacco smoke, has such enduring effects," she writes.
She notes that in a recent analysis conducted by the US Centers for Disease Control and Prevention, it was estimated that roughly 3.7 million high school students and 910,000 middle school students were using tobacco in 2014. Attentional problems are only "one of many concerns" regarding the consequences of cigarette smoking by young people, Dr London says, and "measures to protect the public health of youth are needed."
"Stringent regulations are needed regarding the sale, pricing, and design of tobacco products to limit initiation of their use by youth as well as strong education and public messaging with health warnings and protection of youth from exposure to second-hand smoke. Because of the immaturity of prefrontal cortical resources to guide potentially life-altering decisions, strong regulatory efforts are needed to protect youth," Dr London concludes.
The authors have disclosed no relevant financial relationships.
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Cite this: Teen Smoking May Cause Enduring Attention Problems - Medscape - Oct 13, 2015.