Psychiatric Genetics

The earlier part of this year saw the publication of a number of studies about the genetics of autism, with one scientist speculating about a unified theory of autism.

The July 2008 Nature Genetics has a review of psychiatric genetics that considers progress and controversy. Here is the abstract:

Several psychiatric disorders — such as bipolar disorder, schizophrenia and autism — are highly heritable, yet identifying their genetic basis has been challenging, with most discoveries failing to be replicated. However, inroads have been made by the incorporation of intermediate traits (endophenotypes) and of environmental factors into genetic analyses, and through the identification of rare inherited variants and novel structural mutations. Current efforts aim to increase sample sizes by gathering larger samples for case–control studies or through meta-analyses of such studies. More attention on unique families, rare variants, and on incorporating environment and the emerging knowledge of biological function and pathways into genetic analysis is warranted.

And some more information about genetic tests and psychiatric disorders: In a recent post on Eye on DNA by Dr. Hsien Hsien Lei, describes newly-developed (and, in some cases, still being developed) genetic tests for psychiatric disorders that are being offered by three different companies. Neuromark’s Mark-C will examine two genetic markers, GRIK2 and GRIA3, that appear to increase the risk of suicidal thoughts in people taking antidepressant drug Celexa; Psynomics is offering a test for mutations of genes linked to bipolar disorder and to patient responses to serotonin-based drugs; SureGene “examines a panel of (unspecified) genes and markers that is being marketed to aid in the diagnosis of patients at risk of developing psychosis,” and that may also be used to predict a person’s response to taking anti-psychotic medications. Autism is not a psychiatric condition (though it used to be considered such); some of the issues raised in the development of these genetic tests are relevant to consider, especially if some kind of genetic test for autism is created.Eye on DNA includes a thoughtful comment from a family practice physician, Tim Janzen, on a Genealogy-DNA discussion list. Dr. Janzen notes that attendant anxiety that may arise in some one who receives a positive result on such a test and underscores that these tests indicate a “genetic predisposition”:

Patients who have a family history of mental illness or other conditions already know that they have a predisposition (unless they are adopted). Thus the genetic results will either reinforce the fact that specific patients are at increased personal risk or they will show that they are at lower risk than they might otherwise be. We shouldn’t forget that environment also plays a role in mental health. Drug abuse is one environmental factor that also predisposes to mental illness.

Genetic testing might be incorporated into “treatment algorithms for people with mental illness.” Regarding “environmental factors,” it’s not quite clear what Dr. Janzen is referring to, though he seems to be speaking not so much about factors such as air pollution, but about what potential parents might do, or not do.

Genetic testing is an understandably sensitive topic in discussions about autism: There are concerns about what choices parents might make if there were a prenatal test for autism and as other diagnostic genetic tests for autism are developed. As my son’s communication abilities are limited—–he is not able, yet, to describe his emotions or if his stomach hurts, or how a certain medication might be affecting him—and here other kinds of testing might, or might not be helpful. Indeed, seeking answers about what to do is a motivating reason for why people are in search of a physiological marker for autism.