They symptoms of schizophrenia are divided into positive and negative. Positive symptoms reflect a distortion of normal functioning, and include delusions (bizarre beliefs that appear real but are not.) a sense of being controlled (e.g. by an alien force), auditory hallucinations (e.g. hearing voices), and disordered thinking (e.g. the belief that thoughts are being broadcast to others). Negative symptoms reflect a lessening or loss of normal function, and include affective flattening (a reduction in the range and intensity of emotional expression), alogia (poverty of speech) and avolition (the inability to initiate and persist in goal-directed behaviour). A diagnosis of schizophrenia requires at least a one-month duration of two or more positive symptoms. Negative symptoms often persist during periods of few positive symptoms.
2 b Discuss two or more biological explanations of schizophrenia (25 marks)
Family studies have found that schizophrenia is more common in the biological relatives of a schizophrenic, and the closer the degree of genetic relatedness, the greater the risk (Gottesman, 1991). Twin studies have shown that identical twins have a 48% risk of developing schizophrenia if their twin has the disorder compared to 17% for non-identical twins (Janicak et al, 2001). Adoption studies have shown that 14% of the biological relatives of adoptees with schizophrenia were classified as schizophrenic, compared to only 2.7% of their adoptive relatives (Kety el al 1988). Research in molecular biology has found that schizophrenics are more likely to have defective version of the gene PPP3CC, associated with the production of calcineurin an enzyme that regulates the immune system (Myakawa et al, 2003).
Evidence from genetic studies indicates that even when two individuals share the same genes (i.e. identical twins), there is less than 50% risk of both developing schizophrenia if...