psychology; family relasion studies

family relasion studies
twin studies

Assumptions
Monzozygotic (identical) twins; 100% genetically identical
Dizygotic (fraternal/non-identical) twins; 50% shared genes

Look for 'concordanance rate' i.e; if 1 twin has illness, does the other too?

family relasion studies; twin studies

Holland 1984; Twins and Anorexia.
55% Mz shared Anorexia Nervosa         compared with         7% DZ
implies genetics are factor as MZ have more in common.

if genes were only factor which caused Anorexia; concordanance rate would be 100%, so other factors must be involved to.

Many inherited features are also influenced by our enviroment  e.g; height-food  and intelligence-level of stimulation

family relasion studies; twin studies

'Nature VS nurture'

Enviroment effects all other factors that might have effect whether you have an illness eg; media, peer pressure, social learning.

high levels concordanance for MZ's might be due to sharing same enviroment, not genetics. ie; treated the same, brought up togther

family relasion studies; twin studies

Adoption Studies; Schizophrenia studies
Gottesman 1991. Twin study.
MZ twins with Schiz'nia--> 48% chance other will develop condition
Dz--> 17% chance

Heston 1996
studied adopted kids whose biological moms either had or hadnt got schizo'nia.
5/47 of 'with group' developed s'nia + 4 borderline causes
0/50 of 'without' group developed s'nia