Bye-Bye Bi-Polar: A New Nosology for Psychiatric Disease — What Does It Mean for Genetic Counseling?

Tom Insel, director of the National Institute of Mental Health (NIMH), roiled the world of psychiatry in a blog post (how very 21st Century of him!).  The post concerned the revised Diagnostic and Statistical Manual of Mental Disorders – the DSM V, due out in a matter of weeks – and it was not a good review for the ‘bible of psychiatry’: “Unlike our definitions of ischemic heart disease, lymphoma, or AIDS, the DSM diagnoses are based on a consensus about clusters of clinical symptoms, not any objective laboratory measure.  In the rest of medicine, this would be equivalent to creating diagnostic systems based on the nature of chest pain or the quality of fever. Indeed, symptom-based diagnosis, once common in other areas of medicine, has been largely replaced in the past half century as we have understood that symptoms alone rarely indicate the best choice of treatment.”

“It’s weakness, “ said Insel, “is its lack of validity.”

Wow.  That is a pretty bad weakness.

Insel’s statement is not news to anyone who studies the genetics of psychiatric disease.  Although many psychiatric illnesses have high heritability, it is increasingly obvious that current list of diseases as defined do not line up neatly with genetic risk factors, whether those risks are established through family history or molecular testing.  A first degree relative with obsessive compulsive disease is a risk factor for Tourette’s as well as OCD; a deletion in 22q11.2 is almost equally likely to lead to a diagnosis of schizophrenia or bipolar disease.  We might think of this as overlapping genetic inheritance, but in fact it illustrates how badly our current labels function when it comes to identifying etiology.

What was news was Insel’s plan to re-orient research funding away from the diagnoses defined by the DSM and towards a new system based on biomarkers like genetic findings, gene expression and brain imaging along with categories of phenotypic information like anhedonia or psychosis without regard to diagnosis.  To this end, the NIMH has launched a campaign to establish research domain criteria (NIMH being an arm of government, it has an acronym: LDT EGAP IVDMIA RDoC).  Researchers are encouraged to base their inquires on RDoC that cut may across, or subdivide, traditional diagnostic categories.

NIMH, as virtually every article, blog or twitter post on this subject pointed out, is ‘the world’s largest funder of research on mental illness.’  That makes this a high-stakes announcement, and change of this magnitude is complicated – after all, valid or not, all the existing literature is based on these diagnostic categories.  Ongoing research is based on DSM diagnoses, as is clinical practice, billing and reimbursement.  So to some extent we are stuck with what we have, warts and all, for the time being.  Insel knows this, just as the authors of the revised DSM know that their system is flawed.  The take-home story here is not a fight between two sides, but a demarcation of a significant moment in time, as the ocean liner that is psychiatry begins a slow turn away from labels based on symptoms and towards a alternate world where diagnosis is based on biological causes, markers and measures of disease.

Someday, designations like schizophrenia or major depressive disorder may sound as quaint as rheumatism or dropsy.  For genetic counselors, it presents a dilemma in the near term.  What goes into the pedigree?  We don’t want to make it more difficult, since we know that genetic counselors are already disinclined to tackle psychiatric illness as a part of the family history.  But possibly this too is a symptom and not a cause: perhaps one reason genetic counselors are hesitant to ask about mental illness is that the associations between disease and recurrence risk are too complicated.  Because anything you can say is squishy and vague and threatening and non-specific.  Who likes that?  Not science people.

Would it be an improvement, if we recorded information about phenotype and test results as defined by RDoC?  Do we need to think about that?  Is this simply a research designation, or is it going to bleed into clinical care sooner rather than later?  I don’t have answers for these questions, but I am directing them to the wonderful and small but highly motivated cadre of genetic counselors who work primarily in psychiatric genetics (I know who you are!  No hiding).  Can you weigh in for us on what all this means for genetic counseling?

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