Phobia - PowerPoint PPT Presentation

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Phobia

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MZ concordance usually significantly higher than DZ. Suggests genetic influence. MZ concordance always significantly lower than 100 ... – PowerPoint PPT presentation

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Title: Phobia


1
Phobia
www.psychlotron.org.uk
  • Main symptoms
  • Marked and persistent fear
  • Anxiety response
  • Avoidance
  • Interferes with everyday activities
  • Duration 6 months or more
  • Affects 6-11 of population (more F)
  • Lifetime problem in 10 of cases

2
Explanations of Phobia
www.psychlotron.org.uk
  • Biological
  • Genetics
  • Nervous system abnormalities
  • Psychological
  • Learning theory

3
Genetic Influences
www.psychlotron.org.uk
  • Compare concordances of MZ DZ twins

Same genes Same environment
MZ twins ü ü
DZ twins û ü
  • Greater similarity of MZ twins is assumed to
    indicate a genetic influence

4
Genetic Data (Simple Phobia)
www.psychlotron.org.uk
MZ DZ
Carey Gottesman (1981) 13.0 8.0
Kendler et al (1992) 25.9 11.0
Kendler et al (2001) 15.9 7.7
5
Genetic Data (Simple Phobia)
www.psychlotron.org.uk
  • MZ concordance usually significantly higher than
    DZ
  • Suggests genetic influence
  • MZ concordance always significantly lower than
    100
  • Indicates environmental influence is also in
    operation

6
Twin Studies
www.psychlotron.org.uk
  • Commonly affected by several problems
  • Small samples (NB not always check)
  • Unreliable zygosity tests (early studies only)
  • MZ twins tend to be treated more similarly than
    DZ, which may account for greater similarity
  • DZ twins can be MF, which may be important with
    sex-differentiated disorders (like simple phobia)
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