One evil never comes alone. And you may wonder why some smokers get addicted for life, without the possibility of quitting. A team at Saint Louis University School of Public Health found a genetic link to all this.
"Some people with a history of depression may become smokers as a way of self-medicating. Some people who are smokers
might become depressed when they try to give up cigarettes and can't," said lead researcher Dr. Qiang John Fu, assistant professor of community health in biostatistics at Saint Louis University School of Public Health.
"When I tried to find something to explain this correlation, I discovered the answer lay partly in a person's genes that are associated with conduct disorder, which is extreme rebellious behavior of teens and children. My findings are an alternate explanation about why nicotine dependence and major depression go together." he added.
The same genes that increased a person's likelihood of developing major depression and nicotine addiction were found in those who also had conduct disorder, like stealing, vandalizing, running away from home and fighting. "These people are likely to become addicted to other drugs and behave impulsively," he said.
His team made the analysis on 3,360 pairs of middle-aged, mostly White twins who served in the military during the Vietnam War. 55 % were identical twins who share their whole genetic material and about 45 % were fraternal twins who share from 1 to 99 % of their genes. The twins completed questionnaires, and a mathematical model evaluated the statistic importance of the genes and fo the environment on nicotine addiction and major depression.
"Our data showed that both major depression and nicotine dependence were highly genetically correlated with conduct disorder. The research also helps to explain why smoking seems to run in some families. Maybe Dad and Mom have a certain personality, which is why they may be more likely to smoke or to be depressed. That personality trait may be based in their genes. The research points geneticists in a new direction to determine the influences of a personality trait," Fu said.
The new research could help physicians detect those people which are at risk of developing major depression or nicotine addiction. "When they see people with a history of conduct disorder, they may be able to predict those people who could develop major depression or nicotine dependence," added Fu.
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