Family studies find
individuals who have sz
and whether their
biological relatives are
similary affected more
often that non-biological or
distant relatives
Children with 2 sz
parents have a
concordance rate of
46%, children with
one sz parent 13%
and children with sz
siblings 9%
AO2
many researchers now agree sz runs in
families due to rearing patterns and
factors that are nothing to do with
heredity. Research on 'expressed
emotion' has shown negative emotional
climate and stress experienced by some
sz individuals may trigger sz episodes
SLT suggests
children imitate
behaviours of their
role models and
when they observe
parent is rewarded
with 'get well soon
cards' and hugs etc.
they are more likely
to imitate those sz
behaviours
Twin Studies
AO1
are a unique opportunity to see relative contributions of genetic and
environmental influences. If MZ twins sharing 100% of their genes are
more concordant in trait of sz than DZ twins suggests greater similarity is
due to genetic factors
Joseph 2004 pooled data for
all sz twin studies carried out
prior to 2007 and found a
concordance rate for MZ
twins of 40.4% and DZ twins
7.4%. This supports sz has a
genetic basis
AO2
Concordance rates are
never 100%. MZ twins
share 100% of their
genes so sz cannot be
purely be caused by
genetic factors
Differences between MZ and DZ
twins may be due to
environmental similarity - Greater
concordance between MZ twins
due to greater environmental
similarity. Joseph said could be
due to MZ twins being treated
more similar and encountering
similar environments experiencing
more 'identity confusion'. Sz
concordance rates may be
nothing more thsn environmental
differences distinguishing the two
types of twin
studies in which researchers do not if
they are MZ or DZ find lower
concordance rates for MZ twins
suggesting researchers are bias
making a difference on the diagnosis
Adoption Studies
AO1
to rid difficulties of disentangling genetic
and environmental influences for
individuals who share genes and
environment, studies of genetically
related individuals who have been apart
are used