Interactionist approach

• The interactionist approach is an eclectic approach that suggests schizophrenia can be explained and treated by referring to a combination of biological, psychological and social factors.
• The diathesis-stress model explains that schizophrenia results from an interaction between a vulnerability (diathesis) and an external trigger (stress).
• Vulnerability

  Can predispose the development of schizophrenia
• Genetics

  • The polygenetic explanation suggests a combination of candidate genes (e.g. COMT gene – see Handout 2) can leave individuals vulnerable to developing schizophrenia
• Concordance rate


  The rate at which both twins in a pair are affected by the disorder
• Joseph (2004) conducted a meta-analysis of all twin study data prior to 2001
• The concordance rate was 40% for MZ twins compared to 7% for DZ twins
• MZ twins are genetically identical (same DNA)
• The concordance rate is significantly higher for MZ twins than DZ twins
• The results from the wide-scale study are likely to have high reliability
• The results strongly support the role of genes in schizophrenia
• If schizophrenia was purely genetic, a concordance rate of 100% would have been expected for MZ twins
• The 60% discordance for MZ twins indicates that stress factors must interact with the biological vulnerability (diathesis) for schizophrenia to develop
• Negative experiences


  Can trigger the development of schizophrenia
• Living in a highly urbanised environment


  • The more adverse living conditions of a densely populated urban environment may act a contributory trigger
• A meta-analysis by Vassos et al. (2012) found that the risk for schizophrenia in the most urban environments was estimated to be over twice as likely than in the most rural environments
• Despite many people living in such areas, only a tiny minority develop schizophrenia
• The development of schizophrenia

  May be conditional on stress factor interacting with a pre-existing diathesis factor
• Interactionist explanation of schizophrenia

  Combination of genetic vulnerability (diathesis factor) and parental child-rearing style (stress factor)
• Tienari et al. (2004) study

  1. Compared rates of schizophrenia in children adopted between 1960 and 1979 from Finnish mothers with schizophrenic symptoms (high risk) to a matched control group of adoptees with mothers without schizophrenic symptoms (low risk)

  2. Assessed adoptees at around 12 years and 21 years

  3. Measured adopted family functioning using a family rating scale based on interviews and observations covering aspects such as conflict, empathy and insecurity
• Adoptive-family ratings

  Predicted schizophrenia, but only in adoptees with a high genetic risk and not in adoptees with low genetic risk
• This supports the importance of using an interactionist approach to explaining schizophrenia as it suggests that the contribution of both a genetic vulnerability (diathesis) and family dysfunction (stress) are important in the development of schizophrenia
• Diathesis

  Vulnerability to developing a disorder
• The original diathesis-stress model for schizophrenia (proposed by Meehl) over-emphasises vulnerability in terms of genetic influences
• Other non-genetic diatheses may also predispose an individual to develop schizophrenia
• Brain damage during a problematic childbirth is an environmental factor that can make a child vulnerable to developing schizophrenia
• Verdoux et al. (1998) estimated that the risk of developing schizophrenia later in life for individuals who experienced obstetric complications at birth (e.g. prolonged labour which can cause oxygen deprivation) is four times greater than those who experience no such complications
• Modern diathesis-stress models still support the interactionist explanation of schizophrenia
• Modern diathesis-stress models suggest internal vulnerabilities may be structural or functional rather than only genetic
• Diathesis-stress model


  Model that assumes stress factors which trigger schizophrenia involve negative psychological experiences, such as living in a highly urbanised environment
• Other risk factors linked to biology may also be involved in triggering schizophrenia
• Cannabis use

  Risk factor that interferes with the dopamine system, which has been linked to hallucinations experienced in psychosis
• Studies into risk factors triggering schizophrenia

  • Andréasson et al. (1987) 15-year longitudinal study of 45,570 male conscripts in Sweden
  • Heaviest users of cannabis (more than 50 occasions) had 6 times the risk of developing schizophrenia compared with non-users
• Research into risk factors is often correlational so causality cannot be inferred
• A combination of risk factors is likely involved in triggering schizophrenia
• Interactionist approach

  Allows for free-will
• Diathesis-stress model


  • Accepts that internal factors such genetic predispositions play a part in schizophrenia
  • Explains that this only makes a person vulnerable to developing the disorder
• Genetic factors alone

  Do not biologically determine that an individual will develop schizophrenia
• Genetic vulnerability


  Requires an external trigger
• Knowledge of genetic vulnerability and external triggers enables the individual to make positive life choices to mitigate the development of schizophrenia