I want to use the publication of an article entitled It’s in your genes: The connection between addiction and other disorders to point out how very misleading and incorrect interpretation of scientific studies can be.
When studying the genetic causes of a disease, it’s very useful to know the heritability of that disease. That is, if one child has the disease, what is the likelihood that a sibling also has it? Do the parents have it? Does it run in the family? The frequency (and pattern of inheritance) of the disease helps us to separate environmental vs genetic causes of the disease. All that happens without ever doing any kind of DNA analysis.
For instance, let’s takes the case of mental health.
In the article, two studies are cited in which the following conclusions are made:
Parental concordance for generalized anxiety disorder may be associated with elevated risk for offspring anxiety disorder, above and beyond the risk associated with having one affected parent.1
-and-
There was a strong degree of specificity of familial aggregation of both the anxiety disorders and substance disorders. Rates of conduct disorder and depression were elevated among offspring of all affected parents.2
Oddly enough, the article is titled, It’s all in your genes and contains the sub-heading The Genetics of Mental Health and Addiction. This is no doubt an important subject, and there is certainly plenty of evidence linking genetics and mental health (which I’ll be expanding on). Unfortunately, neither of the research articles cited has anything to do with genetics. In this case being related (read genetically similar) and mental disease are correlated, but correlation is not causation and neither of the articles even makes any mention of genetics! They are clearly discussing the environmental contributions to mental health. So why are they interpreted as a genetics article?
Citations
1: Johnson JG, Cohen P, Kasen S, Brook JS. Parental concordance and offspring
risk for anxiety, conduct, depressive, and substance use disorders.
Psychopathology. 2008;41(2):124-8. Epub 2007 Dec 5. PubMed PMID: 18059114.2: Merikangas KR, Dierker LC, Szatmari P. Psychopathology among offspring of
parents with substance abuse and/or anxiety disorders: a high-risk study. J Child
Psychol Psychiatry. 1998 Jul;39(5):711-20. PubMed PMID: 9690934.
Dear Dr. Rick,
first of all, thank you for reading my post. I have to agree with you that using “all” in the title was a poor editorial choice. I’ll most likely remove it. Still, it seems that you’re suggesting that unless genotyping takes place in a study, no assertions regarding underlying genetic heritability can be made, an assertion with which I have to disagree. Association studies are commonly used to uncover genetic association though, as you stated, association does not mean causation.
I agree with this statement so much, I actually wrote my own article on it at I hope you get a chance to check it out.
All in all, I’m more than happy to have an informed discussion on the topic and welcome any additional comments you may have on any of my articles.
All the best,
Adi
Hi Adi,
Thanks for responding to my article.
You can indeed use inheritance to infer something about the underlying genetic causes of a disease. The problem is with mental health, when the environmental factors are so great and so important, special consideration needs to be taken to distinguish genetic from environmental causes. That was not the focus of either of these papers.
Hopefully I will get a chance to expand on the genetics of mental health in the future.
Stay tuned.
Dr. Rick
Hmmm… Just looked at my post and the “all” was already gone. Less work for me.