Biological Cause of Schizophrenia:
1) Family studies:
THE CLOSER THE BIO RELATIONSHIP, THE GREATER THE RISK OF DEVELOPING Schizophrenia.
Kendler et el: 1st degree relatives are 18x > likely than the G.P. (general population) to get Schizophrenia
X RETROSPECTIVE. (so unreliable data; social desirability/distortions in info).
2) Twin studies: (concordance rate)
48% : 17%.
MZ twins : DZ twins.
58% of twins reared apart were concordant of Schizophrenia.
X Twins share same enviro in womb.
X Twins reared apart is rare.
3) Adoption studies:
7% of 112 adoptees of Schizophrenic bio mothers, and
1.5% of 135 adoptees with non-Schizophrenic bio mothers, developed Sz.
Adoptees with Schizophrenic bio mothers 4x > likely at risk of Schizoprhenia than adopted children with non-Schizophrenic bio mothers.
X Wahlberg re-examined Tineari's data:
Only adopted children who were adopted into family with POOR COMMUNICATION were at increased risk.
X LONGITUDINAL STUDY - diagnostic crtieria always being updated/changed.
X 89% of schizophrnic have NO KNOWN RELATIVE with Schizophrenia, so other may factors cause Schizophrenia.