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Psychiatric Disorder: Is It All In The Genes?

Psychiatric Disorder: Is It All In The Genes?. Peter McGuffin MRC SGDP Centre Institute of Psychiatry, King’s College London. Why might a disorder run in families?. Shared genes Shared environment A combination of the two. behaviour. Natural experiments teasing apart genes and environment.

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Psychiatric Disorder: Is It All In The Genes?

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  1. Psychiatric Disorder: Is It All In The Genes? Peter McGuffin MRC SGDP Centre Institute of Psychiatry, King’s College London

  2. Why might a disorder run in families? • Shared genes • Shared environment • A combination of the two

  3. behaviour

  4. Natural experiments teasing apart genes and environment • Twin studies : is there more similarity monozygotic ( one egg) than dizygotic ( two egg) pairs? • Adoption studies: do individuals resemble their biological relatives more than adopting relatives?

  5. MZ TWINS • MZ (monozygotic) twins have 100% of their genes in common (they’re ‘natural clones’) • Shared environment also makes them similar

  6. DZ TWINS • DZ (dizygotic) twins have 50% shared genes • They also share environment to roughly the same extent as MZ twins

  7. MZ and DZ Twin Similarity Expressed as Correlations

  8. Coaction Interaction Covariation Additive Multiplicative G & E correlated Types of Gene Environment Interplay

  9. Coaction • Phenotype= Genes (G) + Environment (E) Shared Non-shared

  10. GE Correlation Vs Interaction • Correlation: genetic influence on exposure to different environments • Interaction: genetic control of sensitivity to different environments

  11. Finding genes • One of the major benefits of the Human Genome Project is a dense map of markers (“signposts”for genome searching) • Linkage studies use genetic markers track genes in families • Association studies can pinpoint genes in populations

  12. Positional cloning • Linkage(or LD) • location • gene identification • structure and sequence • gene product prediction diagnosis treatment

  13. Specific genes that interact with environments • serotonin transporter, social adversity (and medication) => depression • Monoamine oxidase A,childhood maltreatment => antisocial behaviour • COMT, cannabis => schizophrenia

  14. The impact of genetics: Post genomic psychiatry • targeted & tailored treatments • refined diagnosis • understanding of neurobiology • risk prediction and gene-environment effects • public perception and stigma

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