smokers who have smoked more cigarettes have clear differences in their
brains compared to lighter smokers, according to a new study.
"Earlier studies of older participants showed that the
smokers had structural differences in various brain regions," said senior
author Edythe D London. And in studies of adolescent animals, nicotine damaged
and killed brain cells, added London, from the Semel Institute for Neuroscience
and Human Behaviour at UCLA and the David Geffen School of Medicine in Los
Angeles. "While the results do not prove causation, they suggest that there
are effects of cigarette exposure on brain structure in young smokers, with a
relatively short smoking history," London said.
smoking an epidemic
Six to seven cigarettes per day
She and her team at UCLA mapped the brains of 42 people ages
16 to 21 using magnetic
resonance imaging (MRI) and asked them about their smoking history and cravings. Eighteen
of the participants were smokers. They had typically started smoking around age
15 and smoked six to seven cigarettes per day.
stimulation blunts cigarette craving
There were no clear differences in the brains of smokers
versus non-smokers. However, among smokers, those who reported smoking more
cigarettes tended to have a thinner insula, a region of the cerebral cortex
involved in decision making, according to results published in the journal
Neuropsychopharmacology. The effects seemed confined to the right insula.
Previous studies have suggested the insula plays a central
role in tobacco dependence, with the highest density of nicotine
receptors in the brain.
The researchers also found a thinner insula in the brains of
people who had more cravings and felt more dependent on cigarettes. Their study
was funded by Philip Morris USA, makers of Marlboro and Virginia Slims.
Young people ages 18 to 25 have the highest smoking rates in
the US at 30%, London said. "Because the brain is still undergoing development,
smoking during this critical period may produce neurobiological changes that
promote tobacco dependence later in life," she said. Changing the
structure of the insula may affect future smoking dependence and other
substance abuse. "It is possible that changes in the brain from prolonged
exposure help maintain dependence," she said.
People who start smoking early in life seem to have more
trouble quitting and have more serious health consequences than those who start
later, London said. But since the study only assessed smokers at one point in
time, it doesn't prove that cigarettes changed their brains.
possible that such changes pre-dated the smoking, i.e. they were not caused by
smoking," Dr Nasir H. Naqvi told Reuters
Health in an e-mail. "The only way to know this is to take a group of
adolescents who have never smoked, follow them over time, and then see who
starts smoking, and then compare them to the adolescents who never started
smoking."Naqvi, a substance abuse researcher at Columbia University in New
York City, was not involved in the study.
Less control over cravings
He studies the insula and said that area drives drug
addiction like a "gas pedal" and also controls decision making like a
"brake pedal". Since the insula was thinner in heavier smokers, it
could be they have reduced power over the "brake pedal" and less
control over cravings, he said.
"The key question is whether these changes are
reversible with smoking
cessation, or whether they persist," Naqvi said. But few studies have
measured changes in the brains of people who stop taking a drug." What we
do know is that once you are addicted to smoking, you will always have a high
likelihood of relapse, even if you are abstinent for many years," Naqvi
The study is interesting but quite small, especially for a
study on this age group, Simone Kuhn said. Kuhn studies brain plasticity across
the lifespan at the Max Planck Institute for Human Development in Berlin and
was not involved in the new research. "Between 16 and 21 the prefrontal
cortex changes considerably; this might make research such as this slightly
difficult," she told Reuters Health.
clearly agree that brain structural effects of smoking in adolescence is an
extremely interesting topic that could be used to spice up anti-smoking
campaigns, addressing this age group with scientific facts."
"It would be useful to do this kind of study in a
larger number of people, starting before the initiation of smoking and
continuing with repeated scans," London said. "This is practical. It
just requires funding."
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