Genomics in general practice

Disease specific topics

Mental health conditions

Mental health conditions

PRACTICE POINT

There are currently no specific high-risk gene variants Gene variants are small DNA sequence changes (ie additions, duplications, deletions, substitutions). These variants can have a range of effects: some may cause disease (pathogenic variant), while others do not cause disease but may modify an individual’s risk of disease (i.e may increase risk or provide a protective effect). The vast majority of gene variants are benign and do not result in disease but rather contribute to the differences between people. that are associated with mental health disorders that are useful for predictive testing Pre-symptomatic testing aims to determine whether a person will almost certainly develop a particular genetic condition at some point in the future when symptoms of the condition have not yet manifested (eg Huntington disease). Predictive testing aims to determine whether a person who has no signs or symptoms of a specific condition at the time of testing has a specific pathogenic variant that increases the likelihood they will later develop the condition. Predictive testing is often performed in relation to genetic conditions that are not evident at birth, but have their onset during adulthood, such as some cancers (eg BRCA 1 and 2 testing). Predictive genetic testing in familial cancer syndromes can only be conducted when the family-specific genetic variant is known. Hence, genetic testing must generally first be done on a family member affected with the specific condition. in clinical practice. There are some genetic conditions with increased rates of mental health conditions. An example is the 22q11.2 deletion syndrome where there is an approximately 25% chance of schizophrenia. Generally, there are other features present that indicate the mental health condition is part of genetic syndrome. In such instances referral to a clinical geneticist should be considered. 

Some companies that offer personal genomic testing may include polygenic risk scores for common mental health conditions such as depression.  The clinical utility of such tests remains uncertain.

What do I need to know?

The causes of mental health conditions, such as schizophrenia, bipolar disorder and depression, are multifactorial, and include environmental, social and genetic factors.

Genetic testing

While some genetic variants have been shown to be associated with mental health conditions, there is no genetic test that can predict mental illness with certainty.

Some commercially available genetic tests can be used to tailor drug treatments to individuals with a mental health disorder such as depression (Pharmacogenomics). While there is evidence from trials that such tests have clinical utility, there are currently no Australian clinical guidelines relating to the use of pharmacogenomic tests in clinical practice.

When should I refer?

There is no indication to refer patients (eg couples considering pregnancy) with a family history of mental illness to genetics services.

Further reading

  • Bousman CA, Arandjelovic K, Mancuso SG, Eyre H, Dunlop BW. (2019). Pharmacogenetic tests and depressive symptom remission: A meta-analysis of randomized controlled trials. Pharmacogenomics, 20(1): 37-47
  • International Society of Psychiatric Genetic testing and psychiatric disorders: A statement from the International Society of Psychiatric Genetics. Brentwood, TN: ISPG, 2017. Available at https://ispg.net/genetic-testing-statement [Accessed 10 Mar 2022].
  • Stephen M. Lawrie, Sue Fletcher-Watson, Heather C. Whalley and Andrew M. McIntosh. Predicting major mental illness: ethical and practical considerations BJPsych Open (2019) 5, e30, 1–5. doi: 10.1192/bjo.2019.11
  • Kendall KM, Van Assche E, Andlauer TFM, Choi KW, Luykx JJ, Schulte EC, Lu Y. The genetic basis of major depression. Psychol Med. 2021 Oct;51(13):2217-2230. doi: 10.1017/S0033291721000441.
  • State MW, Geschwind Leveraging genetics and genomics to define the causes of mental illness. Biol Psychiatry 2015;77(1):3–5.
  • Bousman CA, Arandjelovic K, Mancuso SG, Eyre H, Dunlop BW. (2019). Pharmacogenetic tests and depressive symptom remission: A meta-analysis of randomized controlled trials. Pharmacogenomics, 20(1): 37-47

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