Cigarette smokers often say that smoking a cigarette helps them concentrate and that they feel more alert. But years of smoking tobacco may have the opposite effect, slowing the accuracy and speed of a person's thinking ability and lowering their IQ, according to a new study headed by University of Michigan researchers.
long-term smoking and diminished mental proficiency in one hundred and seventy two alcoholic and non-alcoholic men was a surprising finding from a study that originally set out to examine alcoholism's long-term effect on the brain and a persons thinking skills.
While the researchers confirmed previous findings that alcoholism is associated with thinking problems and lower IQ, their analysis also revealed that long-term smoking is too. The effect on problem-solving, memory and IQ was most pronounced among those who had smoked for years. Among the alcoholic men, smoking was associated with diminished thinking ability even after drug and  alcohol use were accounted for.
The findings are the 1st to indicate a direct link between smoking and neuro-cognitive function among men with alcoholism. And, the results also indicate that smoking is associated with a reduced thinking ability even among men who don't have alcohol problems.
 

The new findings, released online before publication by the journa Drug and Alcohol Dependence, were made by a group from the University of Michigan Medical School's Addiction Research Center, or UMARC, and their colleagues at the VA Ann Arbor Healthcare System and Michigan State University.

Lead author Jennifer Glass, Ph.D., a research assistant professor in the University of Michigan Department of Psychiatry, cautions that the findings need to be duplicated by other studies before any conclusions are made about smoking's effect on the brain, or before the findings can be considered relevant to women.