Psychiatry: basic sciences
Psychiatric genetics
Psychiatric genetics studies how genes contribute to mental illness, through family, twin and adoption studies and modern genome research. It helps psychiatrists explain inherited risk to families and understand that genes raise risk but rarely decide outcome.
Depth by stage, Pre-U → Consultant (details)
What is it?
Most mental illnesses run in families to some extent. Psychiatric genetics measures how much of this is due to genes (heritability) and searches for the specific genetic variants involved.
Older methods include family, twin and adoption studies. Newer methods include genome-wide association studies, which show that conditions such as schizophrenia, bipolar disorder and depression are influenced by many genes of small effect, plus some rarer variants of larger effect.
The field also covers genetic syndromes with psychiatric features, interactions between genes and environment, and pharmacogenetics, which looks at how genes affect drug response.
Why does a psychiatrist need it?
Patients and families often ask: 'Will my children get this?' Psychiatrists need to answer accurately and calmly, recognise genetic syndromes that need referral, and read research claims about genetic tests critically. Knowing that genes and environment interact also guides prevention and avoids fatalism.
What level is expected at each stage?
Scale: 1. Aware → 2. Understands → 3. Applies → 4. Masters / Teaches. What the levels mean.
- Pre-UAwareKnows basic Mendelian inheritance and DNA from school biology.
- Pre-clinicalUnderstandsLearns medical genetics, inheritance patterns and chromosomal disorders.
- ClinicalAwareIs aware that psychiatric disorders run in families when taking a family history.
- HousemanshipAwareRecords family history; little specific application.
- Medical officerAwareTakes a detailed psychiatric family history and answers simple risk questions.
- Psych traineeAppliesExplains heritability, study designs, GWAS findings and key syndromes at exam level.
- Specialist / consultantAppliesCounsels families on risk and judges new genetic and pharmacogenetic tests critically.
What are the key topics?
Concepts and methods
- Heritability and its common misunderstandings
- Family, twin and adoption study designs
- Linkage versus association studies
- Genome-wide association studies (GWAS) and polygenic risk scores
- Copy number variants and rare variants
- Epigenetics
Findings by disorder
- Schizophrenia and bipolar disorder: high heritability, shared genetic risk
- Depression and anxiety: moderate heritability
- Autism and ADHD: high heritability, many genes
- Alzheimer's disease: APOE e4 and early-onset single-gene forms
- Alcohol use disorder and genetic variants in alcohol metabolism (relevant in Asian populations)
Genetic syndromes with psychiatric features
- Down syndrome and early dementia
- Fragile X syndrome
- 22q11.2 deletion syndrome and psychosis
- Prader-Willi syndrome
- Huntington's disease
- Klinefelter and Turner syndromes
Gene–environment and clinical use
- Gene–environment interaction and correlation
- Pharmacogenetics: CYP2D6 and CYP2C19 metaboliser status; HLA-B*1502 testing before carbamazepine in people of Asian ancestry
- Genetic counselling: principles and ethics
- Limits of current genetic testing in psychiatry
How is it learned and assessed?
- Genetics teaching in pre-clinical years
- Basic sciences in psychiatry training; examined in MMed Psychiatry Part I and MRCPsych Paper A
- Journal club critical reading of genetic studies
Typical textbooks and resources
- Psychiatric Genetics: A Primer for Clinical and Basic Scientists — Nurnberger and Berrettini
- Emery's Elements of Medical Genetics — general medical genetics
- Oxford Textbook of Psychiatry — genetics chapters
- MRCPsych Paper A revision guides — various authors
Titles are widely used examples; editions change. Use university libraries or legitimate purchases.
Common questions
If a parent has schizophrenia, will the child get it?
Most children of a parent with schizophrenia do not develop it. Their risk is higher than the general population, but genes are only part of the picture, and many other factors play a role. A psychiatrist can explain this in more detail for a particular family.
Why is HLA-B*1502 testing mentioned in Malaysia?
This genetic marker, more common in some Asian populations, is linked to a serious skin reaction to carbamazepine. Testing before starting the drug is recommended in people of Asian ancestry, so psychiatrists in Malaysia need to know about it.