Disturbances of affect - emotional blunting
Psychomotor disorder - e.g. catatonia
Lack of volition or will - withdarws from social situations, inability to make decisions
Family Studies - Gottesman - risk of schizophrenia : Uncle/Aunt - 2% Offspring of 2 schizophrenic parents - 46%
Indicates schizophrenia runs in families, however family members that are closely related tend to spend more time together so, environmental factors cannot be ruled out.
Twin Studies - Gottesman - concordance 46% in MZ and 14% in DZ twins.
Concordance rates not 100% in MZ which would be expected as they share 100% genes; suggests that other factors must play a part
Adoption Studies - Heston - 16% of adopted children with a schizophrenic mother were diagnosed
Biologically deterministic and reductionist