the causes of sz

Question 1

what are the biological factors that can lead to the development of sz?

Answer 1

CT studies-
Johnstone et al 1976- found increased enlargement in the lateral ventricles- indicating LOSS of brain tissue. * findings inconsisent across studies.

Lewis 1990- MRI studies show changes primarily in grey matter and abnormalities in the frontal, temporal and parietal lobes
Newer studies show white matter connectivity abnormalities.

PET studies show significant differences in the frontal lobe

Selemon and Goldman-Rakic 1999- reduced volume of cortical neurophil (axon terminals and dentritic spines) without equivalent neuronal loss supports the role of abnormal neurodevelopment in sz.

however, no consistent evidence that suggests SZ is solely caused by brain structural damage.

Question 2

what are some social class factors that can lead to the development of SZ?

Answer 2

Bentall 2009- rates of sz are increased in lower social classes.
this could be caused by increased stress leading to increased vulnerability or poor nutrition- deficient levels of biological proteins.

social drift hypothesis- sz patients drift down the social ladder due to their symptoms leading to unemployment and poverty- thus ending up in lower social classes.

Question 3

what are some family factors that could cause SZ?

Answer 3

Mischler and Waxler 1968- found poor levels of communication in SZ families- however difficulties in drawing causal inferences from this data.

Vaugn and Leff 1976- observed that some families were highly critical towards the patients and other families were overprotective and over bearing= expressed emotion (EE)

High EE families= at least one member of the patients family was hostile, critical or over involved.

high EE families had a 51% relapse rate within 9 months.
Relapse rate in low EE families was 13%.

implications are limited to the management of Sz.

Question 4

What are some predisposing factors to SZ?

Answer 4

Pregnancy and birth complications:
Jones et al 1998- studies found associations with premature delivery, perinatal brain injury and low birth weight is associated with SZ.

Genetic background:
Daniel Weinberger 2017- compared brain structure and cognitive performance in identical and non-identical twins with SZ.
In the pairs where only one twin had sz- only the affected twin showed brain abnormalities like increased lateral ventricles and cognitive performance.
the unaffected twin didnt show these changes-

leads to questions whether brain pathology and symptoms are due to to genetic factors- genetic predisposition alone is not a good enough explanation.

Question 5

what affect does substance abuse have on SZ?

Answer 5

Curran et al 2004- intermittent and chronic consumption of stimulants such as amphetamine and cocaine can induce psychotic symptoms in healthy individuals and lead to relapses in individuals with sz.

Henquet et al 2005- Regular cannabis use at a young age increases future risk of sz and this effect is moderately strong even after controlling for the effects of self medication.

Question 6

How does the COMT gene influence the way that cannabis affects sz?

Answer 6

The COMT gene affects how the brain breaks down dopamine- key neurotransmitter involved in sz.

two common alleles of this gene-
Valine
Methionine

Caspi et al:
cannabis use increased psychotic symptoms and sz-like illness primarily in people with at least one Val allele (esp val/val genotype)
individuals with two copies of the Met allele (met/met) did not show this increased risk from cannabis use.

The val allele of the COMT gene may increase vulnerability to the harmful psychosis-related effects of cannabis.

these findings support a gene-environment interaction model, where genetics and lifestyle factors like drug use combine to increase sz risk.