Dude, Where's My Smokes?

By Michael Dhar 12/30/13

Nicotine and the teenage brain: New York City targets smoking's favorite victims


Capping off a decade-long crusade against tobacco, outgoing NYC Mayor Michael Bloomberg took a parting shot at teen smokers: In the last month of his final term, Bloomberg signed a bill raising the legal age for buying nicotine from 18 to 21, making NYC by far the largest U.S. locality to do so. More than simply another general restriction on nicotine use, the law targets a group uniquely susceptible to tobacco: much more so than in adults, nicotine changes the teenage brain.

"The young brain is still developing at that age, and it's particularly sensitive to nicotine," said Danny McGoldrick, vice president of research for the Campaign for Tobacco Free Kids. Most importantly, nicotine rewires the teenage brain, programming it for addiction.

The drugs themselves may have as much, or even more, of an effect on behavior as "adolescent behavior" has on drug use. 

"The adolescent brain responds differently to nicotine, because it is wired differently and is biologically different in its drug response," wrote Dr. Theodore Slotkin, professor of pharmacology and cancer biology at Duke University School of Medicine, in an email response to The Fix. "The adolescent brain is more sensitive to nicotine, shows greater reward, [and] less negative effects, reinforcing addiction."

A Learning Machine

Essentially, smoking teaches the brain to be addicted—and the teenage brain is uniquely receptive to that "lesson," said Dr. Slotkin, who developed an animal model of nicotine's effects on adolescents.

"Think of the developing brain (including the adolescent brain) as a learning machine, since that's its major function," Slotkin said. "At the level of brain circuits, 'learning' consists of the reinforcement of certain connections, and that can be permanent," he said, citing the familiar example of learning to ride a bike. "If you reinforce the circuits stimulated by nicotine, you teach the brain to depend on that stimulation."

Slotkin's animal-model studies paint adolescence as a "unique period of vulnerability to nicotine" due to a number of nicotine-induced transformations similarly unique to the adolescent brain. In raising the smoking age from 18 to 21, public health officials hope to get nicotine out of the hands of these vulnerable targets of addiction.

At the level of brain regions, nicotine alters activity in two areas of the adolescent brain particularly important to addiction: the hippocampus, important in learning and memory, and the mid-brain, a center for the reward and addiction pathways. In particular, adolescent female rats treated with nicotine showed evidence of cell damage and changes in cell size in the hippocampus. Male adolescents, in turn, showed cell damage in the mid brain. By contrast, adult rats actually showed decreases in cell death accompanied by cognitive enhancements.

In each case, the rewiring of the brain regions was accompanied by changes to neurotransmitter connections among neurons. Adolescents showed greater increases in nicotine acetylcholine receptors, which are strongly associated with nicotine dependence. Both dopamine and norepinephrine showed deficits during nicotine treatment, and adolescent rats showed long-term reduced sensitivity to these neurotransmitters. These chemicals play a central role in the reward pathway, and thus addiction, Slotkin said.

Young Smokers

Though biological studies, like Slotkin's, of nicotine and teenage brains have been relatively rare, public health researchers have for some time realized the importance of the teenage years for getting smokers addicted. Perhaps more importantly, tobacco companies have long realized it, too, targeting 18-to-20 year olds, McGoldrick said.

In 1986, Philip Morris released a report stating that "Raising the minimum age for cigarette purchaser to 21 could gut our key young adult market (17-20) where we sell about 25 billion cigarettes and enjoy a 70 percent market share."

National data shows that 95% of daily smokers start before age 21, while 80% start younger than 18; as a result, 700 kids under 18 become regular smokers every day. The years between 18 and 21 also mark the time many adolescent smokers transition from experimental to full-time smoking, McGoldrick said.

For public health professionals, then, NYC's latest attempt to get cigarettes out of teenagers' hands thus stands as a cause for celebration, he said. The age-raise will also affect kids younger than 18, who often model the behavior of, and get cigarettes from, 18-year-old high school seniors, McGoldrick said.

Indeed, in NY as elsewhere in the country, older kids tend to serve as a conduit for nicotine. "When I was in high school, a lot of teenagers smoked," said Jamie Frey, 27, a smoker who grew up in Kensington, Brooklyn. "People had older brothers, or they'd find someone older—it was neighborhood kid kind of stuff."

'What Else Can You Do?'

The age-raise takes aim at the last few percentages of teens who still smoke, after decades of other successful anti-smoking policies, McGoldrick said. Adult smoking rates in New York dropped more than 30 percent from 1993 to 2011, with youth smoking rates declining an even greater 57 percent from 1997 to 2011. The declines coincided with aggressive, and highly influential, anti-smoking policies instituted under NYC Mayor Michael Bloomberg, first elected in 2001. The city raised tax rates on cigarettes in 2003; that same year, NY passed a workplace smoking ban, which famously banished smokers from most bars and restaurants. In other policies over the years, the city aired powerful anti-smoking ads starring real-life New Yorkers ravaged by smoking-related illnesses and distributed free cessation aides.

Those policies, in turn, spread throughout the country: 80 percent of Americans now live in places with workplace smoking bans, whereas nowhere outside of California had any similar ban when Bloomberg enacted New York's.

But in recent years, the effects of those policies have stalled, both nationally and in New York, McGoldrick said. "So, what else can you do?" he asked. "We think raising the age is a good complement to the other things going on."

Targeting 18-Year-Olds

The different policies will have to work in concert, McGoldrick said, since no single measure will prove entirely effective. Even given the age increase, set to take effect in six months, some teenagers will still get cigarettes, he said.

Frey agreed, noting that high schoolers in NY always know the neighborhood stores that sell to the under-18 set. That will likely continue with a 21-year-old policy, he said. "Everyone probably had one store in their neighborhood," Frey said. "You just have to know the spot."

Still, the fact of the law itself will convince many teens to, at least, put off smoking, said Kit Freedman, a researcher with the Wyoming Survey and Analysis Center, who studied teen smoking rates for the CDC. "We spoke to a number of young adults who said that because it is illegal before 18, that was a reason not to begin smoking," he said. "There, you see that age laws do have an effect on smoking initiation."

So far, the public has not seemed to turn on the age increase in the same way that they had for some other Bloomberg public health measures. Public discomfort with a ban on large soda sizes, for example, culminated in a state judge striking down the measure this year. Smoking seems a more marginalized, and thus easier target for bans; while 60 percent of New Yorkers opposed the soda ban, that same majority favored the workplace smoking ban when it passed.

The new law still rankles some, however, who see these bans as heavy-handed encroachments on liberties.

"I know that smoking's bad, it affects health and costs money," Frey said. "But I think a lot of these laws are trying to baby people."

Moreover, the limitation of 18-year-olds should offend a population of legal adults, said Janet Hopf, president of the Manhattan Libertarian Party. "Eighteen year olds should be able to decide what to do with their bodies," she said.

Consequences of Biology

Traditionally, observers have chalked up smoking and addiction among teens to juvenile rebellion. Biological studies of nicotine's affects on the developing brain demolish that facile preconception, however, Slotkin said. "My work provides a biological mechanism for the greater addictability of nicotine in the adolescent," he said. "This is in contrast to thinking about it just as 'adolescent behavior' or 'risk-taking' or 'social pressure.'"

In other words, the drugs themselves may have as much, or even more, of an effect on behavior as "adolescent behavior" has on drug use. Animal models, indeed, associate clear behavioral changes with nicotine's impacts on adolescent brain wiring. The neurochemical alterations led to "immediate and delayed behavioral alterations," manifesting as decreased movement and grooming behavior in the rats.

Though it's difficult to extrapolate these specific behavioral changes to human subjects, the hippocampal damage likely explains cognitive impairment seen in adolescent smokers, Slotkin said. And the overall rewiring of reward circuits likely underlies the greater addictability seen in teens, he said.

Important in the effort to curb smoking, these behavioral changes can persist for a long time, and nicotine's rewiring of the addiction pathways can predispose teenagers to other addictions, Slotkin said. "Newer work shows that adolescent nicotine use permanently changes the response to addictive drugs later in life," Slotkin said. "So that smoking serves as a 'gateway' to other abused substances."

21 Everywhere?

Only a few other, much smaller, locations have enacted 21-year-old mandates similar to NY's: the big island in Hawaii and two small Massachusetts towns. But as data from those places, and particularly from NYC, comes in, the age increase could sweep the country, much like NY's workplace smoking ban already has.

Public health advocates will continue to push for age increases, either way—if only because of the convincing evidence that nicotine transforms adolescent behavior long-term, saddling the teenage brain with addiction.

"It took 50 years to get to this point, and we're still loosing 400,000 people per year," McGoldrick said, referring to the annual mortality rate associated with smoking. "We need to try to finish the job."

Michael Dhar is a medical and science writer who has written for Livescience.com, Science & Medicine, Iowa Outdoors and various medical and research institutions.

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