Ancestry, Addiction, and trauma – Addiction research into genetic differences based on race

We all know that drug use and drug related crimes are a big problem within African American communities. It’s not a secret, but it can be interpreted very differently by different people. Do the differences between African Americans and Americans from European descent mean that Black people are simply meant to have more problems?

A recent study suggests that at least when it comes to addictions, the opposite might be true.

A genetic study of addiction and ancestry

Researchers at the New Jersey VA (Veterans’ Affairs) office collected data from 407 addicted African American patients as well as from 457 comparison participants at a local hospital’s ophthalmology clinic. Like in most studies of this nature, both groups was screened for other psychiatric problems and participants from the control group were excluded from the study if they showed any signs of addiction problems themselves.

The researchers then used 186 different genetic markers that relate to ancestry to determine the proportion of African, European, and Asian descent for each participant. After following this up with some questionnaires about childhood trauma and an estimations of participant socioeconomic status (things like income, education, age, etc.), the researchers ran analyses to see if African ancestry was related to drug problems, childhood trauma, and poverty.

The ancestry of the participants was verified to be mostly (average 80%) African, with European, Middle East, and Central Asia contributing between 5% and 7% more.

What did they find?

Addiction research about race and genetics - The proportion of African ancestry among the different groupsThe first interesting finding was the fact that patients with alcohol, cocaine, or opiate dependence had lower proportion of African ancestry than non addicted individuals. The differences ranged from 5% to 3% but certainly reached significance levels. Since its already known that Europeans are more likely to show alcohol, but not drug, problems, the researchers checked to see if that was the factor responsible for the difference – it wasn’t.

Interestingly, even though childhood abuse or neglect were very much related to addiction in this sample (as we’ve talked about before), there was no relationship between African Ancestry and abuse or neglect.In fact, the two factors that were almost significant (childhood physical and sexual abuse) showed trends similar to those for addiction – African descent was associated with lower problems in those areas.

The final, and not surprising finding, had to do with an association between African ancestry and lower socioeconomic status. The differences in these categories were significant for income and education. This finding can almost serve as a validity check on the whole experiment, since census data has long shown lower SES for African Americans in the united States.

What does this all mean?

Okay, I know this isn’t necessarily the easiest study to understand, so let’s break it down:

Given the known drug problems among African Americans, the researchers wanted to know if African descent could have something to do with underlying genetic factors that make it more likely that Black individuals will end up as drug addicts. There are a host of genetic differences between Europeans, Asians, and Africans, and this was a way to get at a lot of them in one shot. The problem is that African Americans are also poorer than many European Americans, and since poverty is a known risk-factor for addiction, meaning it makes it more likely that someone will end up an addict, the researchers were interested in separating the two. They threw trauma in because it, like poverty, has already been shown to be related to addiction.

The results seemed to indicate that the two factors (poverty and addiction) as indeed separate. While African descent was associated with more poverty, it was actually found to be associated with less drug, and alcohol problems. This suggests that it’s the poverty, and all the factors associated with it, that may be driving the higher addiction rates among African Americans and not some predisposition to drug problems.

The good news is that this suggests that efforts at improving the SES and quality of life for African Americans in the United States will indeed lower their substance abuse rates. In fact, when it comes down to it, this research suggests that European Americans are the ones we need to watch for in terms of genetic risk for addiction.

As always, limitations

As usual, we need to remember that these are associations and don’t prove causality. Also, given the very specific sample used (veteran addicts), the results should be replicated in other populations. Lastly, remember that the ancestry-based differences weren’t huge, but given the fact that this was a strictly African American sample, that’s probably part of the package. Again, more research with¬† broader populations should help to resolve that.

Citation:

Francesca Ducci, Alec Roy, Pei-Hong Shen,Qiaoping Yuan, Nicole P. Yuan,  Colin A. Hodgkinson, Lynn R. Goldman, and David Goldman (2009). Association of Substance Use Disorders With Childhood Trauma but not African Genetic Heritage in an African American Cohort. American Journal of Psychiatry, 166, 1031-1040.

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