interactionist approach

what is the diathesis-stress model?

explains mental disorders as the result of an interaction between biological and environmental influences

when are symptoms made worse?

when stressors are combined with biological vulnerability

what have family studies suggested?

people have varying levels of inherited genetic vulnerability to SZ but whether they develop it or not is determined by the vulnerability and the amount or level of stressors they experience

what evidence is there to support the diathesis?

identical twins of people with SZ are more likely to develop SZ - 50% - discordance indicates that environmental factors must also play a role

what are examples of stressors?

• childhood trauma

• stresses from a highly urbanised environment

what did Varese find?

children who experienced severe trauma before 16 were 3x more likely to develop SZ in later life

what did Vassos et al find in their meta-analysis?

the risk for SZ in the most urban environments was 2.37x higher than rural environments but the reason why is unclear

what is the additive nature of the diathesis-stress model?

relatively minor stressors may lead to the development of SZ for a highly vulnerable individual and a major stressor may lead to SZ for someone low in vulnerability

what was Tienari’s aim?

to discover whether genetic factors moderate susceptibility to environmental risk associated with adoptive family functioning

what was Tienari’s procedure?

• hospital records for 20k women

• sample of 145 adopted-away offspring of SZ mothers matched with a sample of 158 adoptees without this genetic risk

• both groups independently assessed after a median integral of 12 years

• follow up after 21 years

• assessed family functioning using OPAS

• blind interviewing psychiatrists to status of bio mother

what does the OPAS do?

measures families on various aspects of functioning such as parent-offspring conflict, lack of empathy & insecurity

what did Tienari find?

• 14/303 adoptees developed SZ during study

• 11/14 were from high-risk group

• low OPAS families had a protective effect for those in high risk group

• adoptive family stress was a significant predictor of SZ in adoptees with a high genetic risk of SZ

what are the strengths of the interactionist approach?

• implications for treatment - genetic vulnerability is hard to control but other factors can be addressed - Borglum: women infected with cytomegalovirus during pregnancy were more likely to have a child with SZ - only if both mother and child had a certain gene defect - suggests antiviral medicine during pregnancy may prevent onset of SZ

what are the weaknesses of the interactionist approach?

• diathesis may not be exclusively genetic - most models emphasise genes - also an increased risk from brain damage - Verdoux: estimated risk of developing SZ for individuals who experienced obstetric complications at birth is 4x higher - brain damage is not genetic

• urban environments are not more stressful necessarily - Romans-Clarkson: no urban-rural differences in mental health in women in NZ - other studies found differences disappeared after adjusting for the socio-economic differences - social adversity may a trigger but not urbanisation

• difficulties in determining causal stress - models make reference to stressful events close to onset - may be earlier events that influence how people respond to later stressors - Hammen: maladaptive methods of coping with stress in childhood and throughout development may mean the child does not develop effective coping skills - compromises resilience and increases vulnerability

what are the limitations of the Tienari et al study?

• assessment of adoptive family functioning - psychiatrists assessed stress using OPAS but only assessed family functioning at one period of time - fails to reflect developmental changes in family over time - admitted