Describe explanations of schizophrenia and delusional disorder.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

1. [3] Genetic (Gottesman and Shields, 1972): Schizophrenia has a genetic cause, evidenced by adoption studies (increased incidence in adopted children with schizophrenic biological parents) and twin studies (MZ 58% vs DZ 12% concordance).
2. [3] Biochemical (dopamine hypothesis): Symptoms may be caused by excess dopamine in the mid-brain and reduced dopamine in the prefrontal cortex, with high D2 receptor activity in subcortical/limbic regions linked to positive symptoms and heightened D1 to negative/cognitive symptoms.
3. [2] Cognitive (Frith, 1992): Symptoms due to faulty thinking processes; patients fail to recognise self-created thoughts (inner voice) as their own, attributing them externally. Delusions may explain hallucinations; cognitive impairment (speech poverty, disorganised thoughts) or less developed theory of mind leads to delusions about others' behaviours.
4. [4] Named issue – Individual versus situational debate: All explanations primarily offer individual explanations, though MZ twin concordance not 100% implies an environmental/situational component. Cognitive explanations (e.g., self-talk) could also be influenced by upbringing and culture.
5. [2] Reductionism: Explanations may oversimplify complex conditions.
6. [2] Nature versus nurture: Discussing the relative contributions of biological (nature) and environmental (nurture) factors.
7. [2] Other evaluative points: Comparisons of different explanations, application of psychology to everyday life (e.g., diagnosis, treatment), evidence to support explanations, or deterministic nature of explanations.