In her
study, "cigarette smoking was negatively related to IQ and
thinking," she said.
This finding
may seem counterintuitive, since many smokers attest to feeling
more alert and focused after smoking. Indeed, research shows
that improved mental functioning is one of the immediate effects
of nicotine exposure. Chronic smoking, however, is known to have
the opposite effect.
Studies show
that up to 87 percent of alcoholics smoke cigarettes, compared
to less than 30 percent of the general United States population.
Yet, few studies have looked into cigarette smoking as a factor
that might explain the cognitive deficits reported among
alcoholics.
To
investigate that association, Glass and her colleagues examined
brain function among 172 men from the same community, including
103 men who abused alcohol.
The team
found that men with higher scores on the lifetime alcohol
problems scale (LAPS) and those who reported a higher number of
pack-years of smoking (i.e. packs of cigarettes smoked per day
times number of years) both had lower IQ scores and lower scores
on a test of global proficiency.
The
proficiency test took into account the speed and accuracy with
which the men were able to perform on a battery of tests
including those that measured short-term memory, verbal
reasoning and mathematical reasoning.
Upon further
investigation, the researchers found that smoking predicted
poorer global proficiency even more strongly than alcoholism
did. Their findings were published online before publication in
Drug and Alcohol Dependence.
Smoking also
appeared to be independently associated with weaker verbal and
visual-spatial reasoning, the study indicates. Thus, though
smoking did not account for all of the decreased neurocognitive
functioning observed among the alcohol abusers, it did seem to
account for some of the effects, the report indicates.
The reason
for the observed associations is unknown, and the researchers
did not investigate the "cause and effect story," Glass said,
but she speculated that the diminished cognitive ability among
smokers may be partly due to some mechanism involving a
restricted flow of blood and oxygen to the brain.
Based on the
current report, Glass said, "if you need another reason to quit
smoking, it's a good potential one to add to the list."
SOURCE: Drug
and Alcohol Dependence, 2005
