Personality and Personality Disorders Personality Personality traits relatively

Personality and Personality Disorders

Personality • Personality traits: relatively stable (across time and situation) individual differences in behaviour • Genes make major contributions (~40%) • Unique environment also important (~60%) • Shared environment has little effect (but…)

Quantifying Personality • Huge number of specific tests, models, designs • Typically self-report questionnaires – E. g. , Myers-Briggs uses 93 forced choice questions, assuming that the individuals are the best judges of their own traits • Traditional theories of personality have put great value on the shared family environment – E. g. , Freudian analysis, Behaviorism, any nurturist perspective

Five-Factor Model • • • Openness to experience (culture) Conscientiousness (conformity) Extraversion (sociability, impulsiveness) Agreeableness (likeability) Neuroticism (emotional instability) Extraversion and neuroticism have received most behavioural genetics research

Self- vs. Peer Report • Most use self-reports • Tends to discount shared environment • Peer reports generally similar on genes and unique, but do suggest greater role for shared environment

Plomin & Caspi (1999) Percentage of variance 100 80 60 40 20 0 self peer Extraversion Neuroticism Unique environment self peer Agreeableness Conscientiousness self peer Openness to experience Shared environment Genetic

Contrast Effects • • • Psychometric methodological issue Correlational studies with twins Parental assessment MZ twins typically high DZ low or sometimes negative Parents contrast fraternal twins, not identical

However… • Lots of personality traits • Intersection between personality and social psychology • Relationships, self-esteem, attitudes • In some cases, shared environment does play larger role

Attachment • • Parent-offspring relationship Strange Situation test Modest heritability Substantial shared environment influence

Romantic Relationships • Waller & Shaver (1994) – No heritable component to styles/type/aspects of romantic love (companionship, passion, etc. ) – 0. 26 for MZ twins and 0. 25 for DZ twins – Shared environment and unique environment are determinants • Text indicates that initial attraction in mate selection also has no heritable component, but there a lot of evolved genetic predispositions and preferences….

Self-Esteem • Linked back to depression (low self-esteem is a core feature of depression) • Like basic personality traits, moderate heritability but limited shared environment effects

Attitudes and Interests • Specific attitudes and interests are learned • Hence, will come from shared or unique environment in the specifics • However, heritable traits can influence what sorts of attitudes/interests are acquired • Consider specific cognitive abilities – E. g. , individual with high mathematical abilities may be better at chess or poker; reinforced, so plays more

Nature via Nurture • Traditionalism (conservative vs. liberal views on wide range of issues) • Twin and family analysis puts heritability at about 50% and shared environment at 15% • Traditionalism could influence religious, political, sexual, etc. attitudes

Personality Disorders • Similarities to psychopathology • Personality traits causing impairment • Generally viewed by individuals as part of their “nature” and not a condition to be treated • Multivariate analysis finds genetic link between personality disorders and major dimensions of personality (especially neuroticism)

Personality Disorders • • • Schizotypal Obsessive-compulsive personality Antisocial Avoidant Borderline Dependent Histrionic Narcissistic Paranoid Schizoid

Schizotypal Personality Disorder • Less intense schizophrenia-like symptoms • Runs in families – Concordance MZ 33%, DZ 4% – Higher proportion of 1 st degree relative schizotypals of schizophrenic probands (11%) than controls (2%) • Danish adoptees: Schizophrenia Schizotypal 1 st degree biol. rel 5% 24% Adoptees & controls 0% 3%

Obsessive-Compulsive Personality Disorder • OCD compulsion is single sequence of bizarre behaviours • OCPD involves general preoccupations of trivial details; interferes with decisions • No really good twin, adoption, or family studies with DSM -IV diagnosis • Twin studies of obsessive symptoms in unselected population show evidence of moderate heritability • Substantial overlap with neuroticism • Obsessive symptoms more common in 1 st deg. rel. of OCD probands (15%) than controls (5%)

Antisocial Personalilty Disorder • Lying, cheating, stealing; highly variable – Irresponsibility, irritability, aggressiveness, recklessness, disregard for truth • Antisocial personality (ASP) – Chronic indifference to and violation of rights of others – Previously often called psychopathy and sociopathy • DSM-IV: history of illegal or socially disapproved behaviour, starting before 15 years and continuing into adulthood, 1% of females, 4% of males (13 -40 years) • Vast majority of juvenile delinquents and children with conduct disorders do not develop ASP disorder

ASP • Runs in families • Adoption studies show genetic, not shared environment factors • 1 st deg. rel. of male and female probands at 5 x and 10 x risk, respectively, whether adopted or not – Disproportionately male disorder; females need greater genetic loading

Antisocial Behaviour • Meta-analysis of 46 twin and adoption studies: shared environment 24%, genetics 40% • Genetic effects increase with age and shared environmental factors decrease • Family members of ASP probands: males at increased risk of ASP & drug abuse; females for somatization disorders

Crime • Criminal records are good data sets to work with • 40% of males & 8% of females with records diagnosed ASP • Two studies find parents with criminal records have increased rates of ASP in their adopted away offspring • Meta-analysis of concordances: MZ 52%, DZ 21% • 3000 Vietnam War veteran US twins (self-reports) shows genetics has negligible effect on arrests prior to 15 years; shared environment has no effect after 15 years • Adoption studies show less heritability than twin studies • Some studies find genetic effects on property crime but not violent crime • Remember XYY discussion re: general cognition…

Genotype-Environment Interaction Adopted sons convicted of criminal offenses (%) • Alcohol abuse increases probability of violent crime Biological parents criminal 25 20 Biological parents not criminal 15 10 5 0 No Yes Are adoptive parents criminal?

Identifying Genes for Personality • Early days • Novelty seeking and DRD 4 (dopamine D 4 receptor) alleleic association • 7 DRD 4 alleles, 2 to 8 repeats of 48 bp sequence (chromosome 11) codes for dopamine receptor, expressed in limbic system • Fewer repeats make protein more effective at binding (in vitro) • Within families, long DRD 4 --> higher novelty seeking behaviour • As if longer repeats make dopamine less effective, so individual seeks more stimulation to release more dopamine

DRD 4 • Variation in DRD 4 explains about 4% of variation in novelty seeking • Longer DRD 4 repeats also show more hyperactivity and heroin addiction • Studies on allelic variation and aggression, shyness, and neuroticism beginning to turn up significant amounts of non-additive genetic variance

Neuroticism • 5 -HTTLPR (serotonin transporter gene) – Linked to neuroticism – Also linked to schizophrenia, depression • COMT valine mutation – Linked to sensation seeking, related to neuroticism • Wide ranging neurotransmitter effects • Conflicting study results re: neuroticism