New Swedish Adoption Study: Genetic and Familial Environmental Influences on the Risk of Drug Abuse

The Archives of General Psychiatry published a new online article on March 5, 2012. The free abstract can be seen here. The conclusion about drug abuse (DA) in the abstract is as follows:”Conclusions  Drug abuse is an etiologically complex syndrome strongly influenced by a diverse set of genetic risk factors reflecting a specific liability to DA, by a vulnerability to other externalizing disorders, and by a range of environmental factors reflecting marital instability, as well as psychopathology and criminal behavior in the adoptive home. Adverse environmental effects on DA are more pathogenic in individuals with high levels of genetic risk. These results should be interpreted in the context of limitations of the diagnosis of DA from registries. ”

CNN  had its review of the study on Monday. When I read the title Adopted kids’ drug abuse risk affected by biological family, I figured that was misleading as CNN loves to interview adoption establishment favorite Dr. Jane Aronson all the time with the same old punchline of original family bad, adoptive family good. I was correct. The title is misleading.

Other medically-focused sources, such as Medical Xpress give the accurate conclusion of the study without the misleading title. It is much more complicated than CNN states. Drug abuse stems from factors of genetics, environment and a genetic-environmental interaction. They say “The authors suggest the risk for drug abuse among children given up for adoption by biological parents, of whom a least one had drug abuse, was 8.6 percent, which they note was “substantially and significantly elevated over that seen in children given up for adoption when neither biological parent had DA (4.2 percent).”

“Risk for DA in adopted children is increased by a history in biological parents and siblings not only of DA but also of alcoholism, major psychiatric illness and criminal convictions,” the authors note.

“Risk for DA in adopted children is increased by disruption in the adoptive parent-adopted child bond by death or divorce but also by a range of indices of a disturbed adoptive home environment and deviant peer influences such as such as parental alcoholism and sibling drug abuse, respectively.”

Researchers also suggest a gene-environment interaction in the etiology (the study of the causes of a disease) of drug abuse.

“Adopted children at high genetic risk were more sensitive to the pathogenic effects of adverse family environments than those at low genetic risk. In other words, genetic effects on DA were less potent in low-risk than high-risk environments,” the authors conclude.

I like to actually go to the source of the study instead of just reading other’s analyses to see how the study was set up and other conclusions that may be important. So I purchased the article and will add some additional thoughts below.

Analysis

First of all, Sweden is a good place to conduct this type of study because they have large databases of information that they can draw from. 18,115 people’s data was used. This was a retroactive analysis of linked information from 9 databasesof information. It is important to understand where this data comes from to understand its value and limitations. Here are the 9 databases:

• Swedish Hospital Discharge Registry from 1964-2009, which includes ALL hospital discharges including for DA
• Swedish Prescribed Drug Register, which includes ALL prescriptions from 2005-2009
• Swedish Mortality Register, which includes all causes and times of death from 1961-2009
• National Censuses for education and marital information from 1960, 1970, 1980 and 1990
• Total Population Registry for education and marital information 1990-2009
• Multi-Generation Register for information on family relationships from 1932 to 2009 including all adoptions and adoptive and biological parents and siblings. Biological siblings reared with the adopted child were excluded
• Outpatient Care Register for outpatient visits between 2001-2009
• Primary Health Care Register for diagnoses and time of diagnoses. This includes outpatient care from 2007-2009 for ONLY Stockholm and middle Sweden (1 million people)
• Swedish Crime Register  for national complete data on all convictions including those forDA from 1973 to 2007.

Which adopted children were in the study?

They selected all people born between 1950 and 1993 who had been adopted ONLY if they had information available on both adoptive parents and at least one biological parent. They EXCLUDED individuals adopted by biological relatives or by an adoptive parent living with a biological parent. It would have been interesting to see a comparison of adoptees raised by relatives to those raised by strangers, but that did not occur.

Age at formal adoption was not available in national records until 1991, so for most adoptees, they had to come up with a calculated guess (adds insult to injury, eh?) called “age at first cohabitation with adoptive parents or AFCAP”  based on census data. In other words, they could be off by several years.

How did they determine the definition of drug abuse?
They used a combination of three criteria from five databases:

(1) Adoptees with the following International Classification of Disease codes in their medical records-discharge or outpatient or primary health care: ICD-8 codes for drug dependence (304); ICD-9 codes for drug psychoses (292) and drug dependence (304); and ICD-10 codes for mental and behavioral disorders due to psychoactive substance use (F10-F19), except those due to alcohol (F10) or tobacco (F17).

(2) Adoptees with crime convictions from the general courts (not minor parking and traffic violations which are not ever listed in the Crime Register) from Crime Register codes 5011 and 5012 which refer to crimes involving DA. They EXCLUDED crimes related to alcohol abuse AND drug trafficking and possession.

(3)Adoptees with certain prescription drug use. They defined drug abuse as 4 or more doses per day for 12 months or more of sedatives, hypnotics or opioids. They excluded cancer patients.

Genetic Risk Score
From the biological parent and sibling data, they created a score based on if they had at least one factor of: DA, criminality as defined as being in the Crime Register for any offense and hospitalization “owing to alcoholism”.

Socioeconomic Status
This was determined based on educational attainment, divorces and mother’s age at birth (or father’s if mother’s age was unavailable). It was ranked as low or high. They explain how they rank low and high for education but not for the other factors.

Environmental Risk
This was measured in factors in the adoptee up to age 20. They looked at adoptive parent variables of DA, hospitalization “owing to alcoholism”, divorce and criminality. They looked at age of the adoptive mother and highest educational status between adoptive mother and father. Hospitalization for any condition, psychiatric illness and death were also included. For the adoptive siblings, DA; hospitalization owing to alcoholism, psychiatric illness, or other medical problems; and criminality were used.

Discussion
The authors of the study felt that their findings replicated a small US study of 197 children published in 1995 and 1996 –Cadoret RJ, Yates WR, Troughton E, Woodworth G, Stewart MA. Adoption study

Their finding of DAin adopted children being predicted not only by DA in their biological relatives, but also by a history of alcohol and psychiatric or criminal problems also replicates prior studies.

In this study, adoptive family risk factors can predict DA in adopted children, namely “disruption of the marital and parent-child bonds through death and divorce, alcohol problems in the adoptive parents or siblings, and criminal behavior and medical hospitalization in the adoptive parents.”

Additionally, “social influences (eg, peer deviance and drug availability) shared with adoptive siblings are more potent environmental risks DA than direct psychological transmission of DA from parent to child.”

The gene-environment interaction is described as follows: “Adopted children at high genetic risk were more sensitive to the pathogenic effects of adverse family environments than those at low genetic risk.”

Limitations include the following:

• Subjects were identified with DA from “medical, legal, and pharmacy records. While this method has the important advantage of not requiring accurate respondent recall and reporting, it could produce both false negative (individuals with DA who never had medical or legal attention) and false positive diagnoses (individuals arrested or treated for a drug problem without having DA or being treated for chronic pain with very high doses of opiates). “
• The definition of DA “may be broader than the definition of drug dependence operationalized in DSM-IV.”
• “nonrandom placement of adopted children can bias adoption studies.”
• “bias can also arise in adoption studies from extensive contact between the adopted children and biological parents prior to adoption. We had to approximate AFCAP from census records available every 5 years. We know that at least 70.9% of adopted children were living with their adoptive parents by age 5 years. However, during the years of our study, adopted children were  typically removed shortly after birth from the biological mother and placed in a special nursery home. Often prior to formal adoption, the child would be placed for trial periods in foster homes. Thus, prior to placement in the adoptive home, adopted children in our sample were more likely to be in the special nursery or foster homes than with their biological parents.” [This is a very big limitation as they did not track the number or quality of prior foster home placements. It could very well be that THOSE experiences contributed more to DA than anything to do with the biological family.]

Final Thoughts

Another limitation that I see in this study is that illicit drug use that is not tracked by these records is not included. The database is only estimated to contain about 20 percent of the drug abusers according to Drug abuse on the rise in Sweden [The Local 8/26/10]: “the report shows that 65,000 people abuse prescription drugs while 80,000 are “risk consumers” of illegal drugs, with a further 29,500 suffering from serious abuse.

Larsson writes that the hidden statistics behind drug and alcohol abuse are considerable with only 100,000 of the total 500,000 abusers known to the healthcare services.”

A 2008 article indicates high rise of alcohol use in the past decade.   Alcoholism in Swedish women increases by 50pc [Telegraph 9/2/08 by David Sarjent] says ” Figures show that between 2003 and 2007 the number of female alcoholics surged by 50 per cent to 100,000, while alcoholism amongst men rose by 25 per cent to 165,000 during the same period.” Are the adoptee DA numbers rising with this statistic?

All in all, I think this was a good study that hopefully will shape future studies on this topic.

What should we take away from this study? I believe that this shows (again) the great need for all adoptees to have their medical records/history as soon as possible as there are some important predictive factors for DA. Additionally, this emphasizes the need to have strong homestudies to rule out adoptive families that have unstable marriages and psychiatric issues because that also leads to DA of adoptees.

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