Causes of Schizophrenia

Schizophrenia is a genetic illness and is therefore passed down through families, we can study this through twin studies, family studies and adoption studies.

- Joseph (2004), found concordance rates for MZ twins to be 40% and DZ 7%. However if it was solely genetics we would expect concordance rates to be 100% in MZ twins. (supported by Gottesman who found similar stats). However, twins live in similar environments so it is unknown whether genetics play the role in concordance rates or whether it's the environment,

- Rosenthal (1963), studied quadruplets that were all diagnosed with schizophrenia at some time in their life, shows that genetics does play a significant role. Also, mom and dad also showed signs of schizophrenia, supporting the idea that it is passed through genes. However, the girls didn't all suffer at the same time and same severity- environmental factors played a role such as favourtism. Case study: lacks generalisability

- Tienari (2000), adoption studies showed that 6% of adopted children with biological mothers who had schizophrenia got the mental illness, but this number was reduced if they were brought up in a supportive adoptive family. Only 2% of the CG got schizophrenia (didn't have schizophrenic moms)

DIATHESIS STRESS MODEL 

- Freud believed that schizophrenia was due to the ego being overwhelmed by either the id or the superego. In response the ego reduces back to infancy and struggles to gain back control, explaining the hallucinations and delusions as an attempt to grasp reality. Freud also says that schizophrenics are driven by their sexual desires which is why it develops in late teens.

HOWEVER... this theory is not falsifiable, and ignores all biological explanations. Despite this, it would explain the concordance rates between MZ and DZ twins as childhood experiences.

- Sterlign and Hellewell (1999), schizophrenic behaviour is not similar to infantile behaviour.

- Double Bind Theory (Bateson 1956) members of families of schizophrenics communicate in a destructive fashion e.g. saying 'I love you' in a tone that sounds angry. However there is very little evidence to support this theory.

- Berger (1965), found that schizophrenics reported a higher recall of double bind statements by their mothers than non-schizophrenics. However, this isn't reliable because of social desirability bias, they might not be able to recall truthfully.

- Interpersonal Communication (Kavanagh 1992) found that schizophrenics in families with high expressed emotion were more likely to relapse than ones in those with low expressed emotion, this is because they need support and stability. However, this is about the recovery of schizophrenia and doesn't show how it is developed.

- Day et al (1987), found that people with schizophrenia are more likely to have suffered from more stressful life events. However this can be interpreted in two different ways e.g. schizophrenia is caused by stressful life events or, people with schizophrenia can't cope with mildly stressful life events like normal people can. (Van Os et al 1994- found no significant link with schizophrenia and stressful life events)

DIATHESIS STRESS MODEL