Illicit Drug Use and Abuse May be Genetic

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ILLICIT DRUG USE AND ABUSE MAY BE GENETIC
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Findings replicated in twin study based in Norway – a country with lower prevalence of drug use than the United States and Australia</i>
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RICHMOND, Va. (July 5, 2006) – Researchers have found that genetic factors may play an important role in a person’s use, misuse or dependence of illicit drugs like marijuana, stimulants, opiates, cocaine and psychedelics.

In the July issue of the journal Psychological Medicine, Virginia Commonwealth University researchers, in collaboration with researchers from Norwegian Institute of Public Health and University of Oslo in Norway, reported the results of a population-based study of twin pairs that showed that genetic factors influence the illicit drug use in Norway, a country with significantly low levels of psychoactive substance use disorder.

“Prior twin studies of illicit drug use and abuse have all been conducted in Anglophonic countries, specifically the United States and Australia, with high levels of such use. This is the first study of a non-English speaking country with much lower rates of drug use - yet results are similar - drug use and abuse or dependence is quite heritable,” said lead author Kenneth S. Kendler, M.D., a professor of psychiatry and human genetics in VCU’s School of Medicine.

The team examined the role of genetic and environmental factors in the progression of psychoactive substance use and abuse.

Approximately 1,400 young adult twin pairs from the Norwegian Institute of Public Health Twin Panel were interviewed and assessed for their lifetime use of illicit drugs, including marijuana, stimulants, opiates, cocaine and psychedelics. Researchers defined the significant lifetime use of illicit substances as use 10 or more times.

Previous theories have suggested that genetic factors might be of less importance in influencing drug use in societies where drugs were not widely available. According to Kendler, the results of this study are inconsistent with this theory.

“In addition to prior findings, the results of this investigation indicate that genetic factors are likely to be important risk factors for psychoactive drug use and misuse in many parts of the world,” he said.

This work was supported in part by grants from the National Institutes of Health, the Norwegian Research Council, the Norwegian Foundation for Health and Rehabilitation, The Norwegian Council for Mental Health and the European Commission.

Kendler collaborated with Steven H. Aggen, Ph.D., in the department of psychiatry at VCU; and Kristian Tambs, Ph.D., and Ted Reichborn-Kjennerud, M.D., who are affiliated with the Division of Mental Health and Institute of Psychiatry, Norwegian Institute of Public Health; and University of Oslo Norway.

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About VCU and the VCU Medical Center: Located on two downtown campuses in Richmond, Va., Virginia Commonwealth University ranks among the top 100 universities in the country in sponsored research and enrolls 30,000 students in more than 180 certificate, undergraduate, graduate, professional and doctoral programs in the arts, sciences and humanities in 15 schools and one college. Sixty of the university’s programs are unique in Virginia, and 20 graduate and professional programs have been ranked by U.S. News & World Report as among the best of their kind. MCV Hospitals, clinics and the health sciences schools of Virginia Commonwealth University compose the VCU Medical Center, one of the leading academic medical centers in the country. For more, see www.vcu.edu.

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More evidence of genetic links to drug abuse

Study tracked marijuana, cocaine use by young adult identical twins

Reuters
Updated: 10:43 a.m. PT July 12, 2006

NEW YORK - A study conducted in Norway provides more evidence that genetic factors may play an important role in the use of drugs such as marijuana and cocaine.

According to study chief Dr. Kenneth S. Kendler, previous studies on the role of genes in illicit drug use were conducted in countries with high rates of drug abuse, namely the United States and Australia.

“This is the first study to show the importance of genetic factors in a culture/country (Norway) with rather low rates of drug problems,” explained Kendler, who is from the Medical College of Virginia in Richmond.

“It has been suggested that in such countries, social rather than genetics factors should prove to be most important. Our results do not support that hypothesis,” he said.

Kendler’s team interviewed and assessed 1,386 Norwegian pairs of young adult twins about their lifetime use of illicit drugs, including marijuana, stimulants, opiates, cocaine, and psychedelics. They report their findings in the journal Psychological Medicine.

The findings overall, Kendler told Reuters Health, provide “rather strong evidence that individuals differ in their risk for drug abuse, that this difference is rather strongly influenced by genetic factors and this pattern of findings occurs in cultures with both low and high rates of drug abuse.”

As expected in this Norwegian population, “significant lifetime use” of illicit drugs, defined as use 10 or more times, was relatively uncommon, being reported by 6.4 percent of the total sample.

The tendency for twins to both take up illicit drug use was much higher in identical twins than in fraternal twins. A diagnosis of psychoactive substance use disorder in both twins, although rare, was also much more common in identical twins than in fraternal twins.

Identical twins are monozygotic, coming from the same egg that splits after fertilization, and they share the same genetic makeup. Fraternal twins are dizygotic, meaning two eggs were fertilized simultaneously, and they are no more genetically alike than non-twin siblings.

Estimates of the “heritability” of illicit drug abuse were high, ranging from 58 to 81 percent, the authors report.

“In addition to prior findings, the results of this investigation indicate that genetic factors are likely to be important risk factors for psychoactive drug use and misuse in many parts of the world,” Kendler concluded in a press release.

Copyright 2006 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content is expressly prohibited without the prior written consent of Reuters.

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Children Of Smokers More Likely To Have Behavior Problems, Smoke And Use Drugs In Adolescence And Adulthood

Medical News Today
14 Aug 2006

A new study exploring smoking, heavy drinking and marijuana use across three generations indicates that the children of a parent who uses any of these substances are more likely to smoke, binge drink or use marijuana in adolescence and adulthood. Drug transmission across generations, the study found, was for a general tendency to use these substances rather than to use any one specifically, with the exception of tobacco.

The children of cigarette smokers face an especially murky future, according to the University of Washington study published in the current issue of the Journal of Abnormal Child Psychology.

"If your parents were smokers it is a double whammy because you are more likely to use drugs in general and even more likely to smoke cigarettes," said Karl Hill, a research associate professor at the UW's Social Development Research Group and co-author of the new study. "There is something about tobacco that if parents smoke, their kids are more likely to smoke. It may be that parents who smoke might leave cigarettes around where their children can see and get to them. Parents may not leave marijuana and alcohol around in the same way."

Data from the paper were drawn from two long-term UW studies, the Seattle Social Development Project and the Intergenerational Project, which are tracing youth development and social and antisocial behavior. Participants were recruited from Seattle elementary schools, and 808 students have been followed since 1985. In addition to the participants, who make up generation 2, data were collected from their parents (generation 1) and their children (generation 3).

The researchers also found a transmission link between the three generations - child behavior problems such as conduct disorder (getting into fights, stealing) attention deficit disorder (lack of focus, can't sit still or maintain attention) and oppositional defiant disorder (problems with authority).

"Children of smokers, heavy drinkers or marijuana users are more likely to have behavior problems when they are young, and consequently more likely to have drug problems themselves as they get old," said Jennifer Bailey, lead author of the study and a UW research scientist. "These children then grow up to be adult substance users, whose kids have behavior problems and the cycle is repeated."

The researchers found that the link between general substance use and childhood behavior problems held up even when they controlled for such variable social factors as marital status, education and neighborhood conditions.

However, they noted the popular notion that the children of substance users are fated to grow up using drugs is wrong.

"Many people think that drug-using parents will have drug-using kids, but the effect is only modest and far from being deterministic," said Bailey. "A lot of children whose parents are smokers, heavy drinkers or marijuana users do not go on to be drug users or drinkers."

Bailey and Hill believe their findings have strong practical applications in breaking the intergenerational cycles of drug use. "This means we don't have to tailor intervention programs for individual drugs except tobacco. These findings suggest that a general substance abuse educational program with an emphasis on tobacco should be effective," said Hill.

Bailey added that prevention programs for chronic and severe child conduct problems also need to be continued and may aid in interrupting the intergenerational transmission of substance use.

The benefits of successful interventions "may echo across generation" the researchers wrote, noting the negative effects of substance use by grandparents are observed not only in their children but also in their grandchildren.

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The National Institute on Drug Abuse funded the research. Co-authors of the paper were Sabrina Oesterle, a research assistant professor at the Social Development Research Group, and J. David Hawkins, former director of the research groups and a professor of social work.

For more information, contact Bailey jabailey@u.washington.edu or Hill khill@.washington.edu

Contact: Joel Schwarz
University of Washington

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Source: Society for Research in Child Development
Date: February 7, 2007

Parents' Genes, Not Parents' Arguing, May Cause Children's Conduct Problems

Science Daily — Children's conduct problems--skipping school, sneaking out of the house, lying to parents, shoplifting, or bullying other children--are a major source of concern for parents and teachers. As a potential cause of these problems, parents' marital conflict has received a lot of research attention. Now a new study finds that parents' fighting may not be to blame but rather that parents who argue a lot may pass on genes for disruptive behavior to their children.

The findings are published in the January/February 2007 issue of the journal Child Development.

A group of researchers from the University of Virginia and several other universities looked at this question, studying 1,045 twins and their 2,051 children. Some of the parents were identical twins and shared all of their genes and some were fraternal and shared only half of their genes. The study found that parents' fighting is not likely a cause of children's conduct problems. On the other hand, parents' genes influenced how often they argued with their spouses and these same genes, when passed to their children, caused more conduct problems.

"This study suggests that marital conflict is not a major culprit, but genes are," said K. Paige Harden, the lead researcher and professor of psychology at the University of Virginia. "Our findings have potential implications for treating conduct problems: Focusing on a child's parents, as is common in family therapy, may not be as effective as focusing on the child."

The study was supported, in part, by grants from the National Institute on Alcohol Abuse and Alcoholism and the National Alliance for Research on Schizophrenia and Depression.

Summarized from Child Development, Vol. 78, Issue 1, Marital Conflict and Conduct Problems in Children-of-Twins, by Harden, KP, Turkheimer, E, and Emery, RE (University of Virginia), D'Onofrio, BM (Indiana University), Slutske, WS (University of Missouri), Heath, AC (Washington University, St. Louis), and Martin, NG (Queensland Institute of Medical Research). Copyright 2007 The Society for Research in Child Development, Inc. All rights reserved.

Note: This story has been adapted from a news release issued by Society for Research in Child Development.