Early Smokers More Addicted

Nicotine dependence worse in people who start earlier based on twin study

/ Author:  / Reviewed by: Robert Carlson, M.D

(RxWiki News) Twin research studies help scientists see the difference between genes and environment. With smoking, these studies highlight how addictive nicotine itself really can be.

In a recent study of identical twins smoking behaviors and nicotine addictions were examined. These twins had started smoking at least 2 years before the second twin picked up smoking.

The results showed that unlike drug and alcohol dependence, nicotine dependence appeared to be worse in the twin that started smoking earlier.

"Talk to your kids, smoking is addictive."

Kenneth S. Kendler, MD, from the Department of Psychiatry at Medical College of Virginia at Virginia Commonwealth University in Richmond, VA, led an investigation into when people started smoking in relation to nicotine dependence later in life.

“Compared with those who start smoking later in life, individuals who begin smoking at a young age are at substantially (much) higher risk for subsequent (following) nicotine dependence,” said the authors.

For this study, 244 identical twin pairs were interviewed about their smoking habits. The twins were recruited from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders.

In all of the twin pairs selected for the study, one of the twins had started smoking at least 2 years before the second twin started smoking.

The average age for the first twin to start smoking was 16 years old, followed by 21 years old for the second twin.

The first of the twins to start smoking was also the first to start smoking heavily. The first smoking twin also had higher scores on a nicotine dependence scale and had stronger cravings for cigarettes when they couldn’t smoke.

These results were found in both male and female twin pairs.

When tested for substance, alcohol and marijuana abuse or dependence, no differences were found between the two twins in each pair.

By comparing nicotine habits to other types of substance abuse, the researchers were able to show that increased nicotine dependence was not genetic, but rather a result of starting smoking earlier in life.

“[T]hese findings suggest that in humans, early nicotine exposure directly increases level of later nicotine dependence,” concluded the authors.

The authors recommended further studies explore the risks involved with early onset smoking habits.

The authors suggested strict regulation to keep cigarettes out of the hands of minors.

This study was published in April in The American Journal of Psychiatry.

The National Institutes of Health, the Virginia Foundation for Healthy Youth and the Virginia Commonwealth University Center for Clinical and Translational Research supported funding for this project. No conflicts of interest were found.

Reviewed by: 
Review Date: 
April 5, 2013
Last Updated:
April 9, 2013