Smoking can lessen IQ, thinking ability: study

By Charnicia E. Huggins

NEW YORK (Reuters Health) – The poorer mental function seen
among alcoholics, many of whom also regularly smoke cigarettes,
may be partially due to the long-term effects of nicotine, new
research suggests.

“People who are also smokers are at a much higher risk,”
Dr. Jennifer M. Glass, of the University of Michigan’s
Addiction Research Center, told Reuters Health.

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