Classification and diagnosis
Schizophrenia (sz) is a psychotic, mental disorder that affects 1% of the population
Sufferers cannot distinguish between reality and their imagination
DSM criteria - 1 positive symptom for at least 6 months OR 2 or more negative
symptoms for at least a month
o Positive symptoms (addition) - hallucinations (visual or auditory), delusions
(paranoia or grandeur), disorganized speech
o Negative symptoms (losing something) - avolition (difficulty to keep with goal
related activities), speech poverty or alogia (reduction in speech)
Issues in diagnosis
Reliability The extent to which different assessors agree on the diagnosis
(consistency)
Validity The accuracy of the diagnosis (criterion - whether different
assessments arrive at the same diagnosis)
Co-morbidity 2 or more conditions at the same time (validity weakness)
Buckley et al - 50% of sz patients also have depression
Gender bias Since the 1980s, men have been diagnosed more with sz
Female patients tend to function better, so different diagnosis given
Symptom overlap When 2 or more conditions share symptoms (validity issue)
e.g. sz and bipolar disorder
Culture bias African-Americans much more likely to be diagnosed with sz in the
UK (some positive symptoms of sz are normal with their culture)
DSM tried to eliminate this - culture bound syndromes (e.g. Koro in
China, Malaysia and Indonesia)
Biological explanations
Genetics Neural correlates
Sz is passed down generations
Dopamine hypothesis: high
Candidate genes (make people levels = sz
predisposed towards developing sz) Excess number of dopamine
Polygenic - multiple genes involved receptors
Mesolimbic = positive
Gottesman found that people with sz in symptoms
general population is 1%, monozygotic Mesocortical = negative
twins is 48% (shared risk), dizygotic twins symptoms
is 17% and siblings is 9%
Adoption studies can separate Abnormally large ventricles in
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