Download Genetic explanation of Schizophrenia

GENETIC EXPLANATION
OF SCHIZOPHRENIA
CLINICAL:
CONTENT
GENETIC INHERITANCE
 schizophrenia is a
heritable condition that
passes down from one
generation to the next
 Twin, adoption and familial
studies clearly points to a
genetic component in
schizophrenia
 this explanation looks at
how genes affect brain
development and may be
partly responsible for
symptoms of
schizophrenia.
NO ONE GENE FOR SCHIZOPHRENIA
Specific genes have not
been shown to directly
cause schizophrenia,
BUT, numerous studies
have shown a variety of
chromosomes to be
involved in the
inheritance of
schizophrenia
WHICH CHROMOSOMES?
 chromosomes thought to
contain these genes
associated with increased
risk of schizophrenia: 22,
1, 18, 15, 14, 13, 12, 11,
10, 8, 6, 5, 3
 many specific regions on
these chromosomes have
also been identified
 Some of the strongest
evidence to date suggests
the importance of
chromosomes 13 and 6.
700 GENES ASSOCIATED WITH
SCHIZOPHRENIA
 Numerous individual
genes are thought to
increase the chance of
an individual developing
schizophrenia
 These include genes that
regulate neurochemicals
such as dopamine and
serotonin
 Currently, research
suggests around 700
genes that are
associated with
schizophrenia,
 (Write, 2014).
CHROMOSOME 22 AND DIGEORGE
SYNDROME
 Potentially there may be
subsets of schizophrenia,
where specific symptoms
are triggered by different
gene abnormalities
 the deletion of a specific
region of chromosome 22,
containing around 30-40
genes, causes a syndrome
known as DiGeorge
 as many as 1 in 4 people
with DiGeorge develop
schizophrenia.
THE COMT GENE
 A specific gene called
‘COMT’
 found on region
22q11.21)
 provides instructions
for the creation of the
enzyme (catechol-Omethyltransferase)
which breaks down
neurotransmitters
such as dopamine
COMT DELETIONS
 deletion of the COMT
gene would mean
dopamine levels are
not controlled
effectively
 If this happens in
regions such as the
frontal lobes,
hallucinations and the
characteristic loss of
reality associated
with psychosis can
result
DISC1 ABNORMALIT Y
 the gene “Disrupted-inSchizophrenia 1” or DISC1 is
important for brain
development and the
neurotransmitter GABA
 People with DISC 1
abnormalities are 1.4 times
more likely to develop
schizophrenia than people
without this abnormality
 Remember GABA is
important in regulating
dopamine levels in the mesolimbic pathways and links to
positive symptoms
LIABILIT Y NOT CERTAINT Y
 schizophrenia certainly
seems to have a heritable
component
 But what is inherited is a
liability rather than a
certainty of developing the
condition
 e.g. the person has
heightened chance
(predisposition) IF, in
addition, they are exposed
to a certain set of
environmental risk factors