Illicit Drug Use among Twins

Illicit Drug Use among Twins

Scientists are increasingly researching the impact of genetic disposition on substance abuse. Understanding to what extent behaviors are programmed in a person’s DNA may help target individuals for awareness education.

One strategy for studying the genetic disposition of certain traits that lead to behavior pathologies involving substance abuse is the examination of twins. A recent study looked at the illicit drug use among Finnish adolescent twins to see if there was a causal relationship or correlated liabilities.

The study by Huizink, Levalahti, Korhonen, Dick, Pulkkinen, Rose and Kaprio was published in 2010. It compared two models among adolescent Finnish twins. The first model describes a direct impact of liability to tobacco use on cannabis and other illicit drug use. The second model included a shared underlying liability for the same substances.

Another objective of the study was to examine the extent to which genetic and environmental influences contributed to the covariation between liabilities to use the substances.

The researchers examined the use of tobacco and illicit drugs at the age of 17.5 years. Twin data was analyzed on 3,744 participants using standard biometrical methods. In addition, two alternative multivariate models were fit and compared with Mx, a statistical program for genetic model fitting.

The results of the study show that the multivariate model provided the best fit to the data. This included the direct impact of the initiation of tobacco use on illicit drug use.

In the model, the variation in the age of initiation of illicit drug use was broken down to several factors, including genetic factors (32 percent), common environmental factors (20 percent), unique environmental factors (8 percent) and a component due to initiation of smoking (40 percent).

The initiation of smoking and illicit drug use provided the most variation in the progression of illicit drug use.

The information provided by the study has important implications for the understanding of causal relationships and correlated liabilities as factors in substance abuse. The study shows that liability to initiate smoking directly affects illicit drug use.

The study indicates that there are several common genetic influences that may be related to tobacco and illicit drug use. Further research may include the examination of specific genes to find those that may be responsible for underlying illicit drug use.

Understanding the specific genes that lead to illicit drug and tobacco use may be very beneficial in targeting for intervention those who are predisposed to behavioral pathologies underlying substance abuse.

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