Biological Explanations

Genetics

The fact that schizophrenia tends to run in families is a clue that it has a genetic basis.

According to the genetic hypothesies

It has a high heritability meaning… the risk of developing the disorder is greater if you have a blood relative with it.

There is no ‘schizophrenia gene’ however, a collection of gene locations have been associated with a higher risk of developing schizophrenia.This means it is thought to be a polygenic disorder.

Gottesman

Reports that while the rate of schizophrenia in the general population is 1%

Buttt…..

If one parent has schizophrenia there is a 12% chance

If both parents have it there is a 40% chance

Implies that schizophrenia is polygenic.

Concluded…

Concordance rates increase with genetic relatedness, supporting the genetic argument.

If there was no genetic element there owuld be no different in the level of risk between relatives and random member of th public.

Twin Studies

Gottesman and Shields

Twin studies offer a unique opportunity for researchers to investigate the relative contribution of genetic and environmental influences.

Aim

To find out if there is a genetic basis for schizophrenia. Also, to replicate previous twin studies into schizophrenia to test their reliability. In particular, the researcher looks for concordance rates in MZ twins where one suffered from schizophrenia and compared these to concordance rates in DZ twins to see if there was a significant difference which would be explained by genes.

Results

In every category, there was a significant difference between MZ and DZ twins, with MZ twins being more likely to share a similar diagnosis of mental illness. The concordance was stronger for female twins than male twins and also stronger with more severe schizophrenia.

For severe schizophrenia (involving 2+ years in hospital), the concordance rate for MZ twins was 75%, but only 24% for DZ twins.

Conclusion

  • The closer the genetic link, the more likely both twins are to show schizophrenic symptoms.
  • However, the MZ concordance rate was significantly lower than 100%. This means that, despite their shared genotype, MZ twins do not always share schizophrenic symptoms.
    - This suggests that genetics is not the only cause of schizophrenia.

Conclude that genes may predispose a person towards but there needs to be an enviuromenal trigger. This is called the diathesis stress model put forward by Rosenthal 1963

…

Critics point out that environment can lead to schizophrenia too: child abuse, neglect, bullying, drug and alcohol problems, all play a part. Often, if one twin suffers these things, the other one does too. However, there might be all sorts of reasons other than genes why one twin might "rise above" these difficulties but the other has a breakdown.

The Dopamine Hypothesis

Neurotransmitters

  • These are fast chemical messengers that travel between neurons by crossing the synapse cleft.
  • They bind themselves to receptors on the post synaptic nausea and pass their message on in the form of an electric charge.

Dopamine

  • It is an important neurotransmitter that regulates mood and attention.
  • It is linked to schizophrenia.

The Dopamine Hypothesis

it was proposed by Arvid Carlosson and suggests that schizophrenia is caused by too much dopamine or too many dopamine receptors in the brain;

Drugs that increase dopaminegric activity

Amphetamine is a drug that stimulates nerve cells containing dopamine causing the synopses to be flooded with this neruotrbamutter.

Essentially

Increased dopamine activity and reduces schizophrenia like symptoms.

Drugs like LSD< which are known to increase dopamine activity also trigger schizophrenia Symptoms in healthy people.

This supports the role of dopamine levels in schizophrenia symptoms.

Drugs that decrease dopaminergic activity

These block the activity of dopamine in the brain… they are ANTIPSYCHOTIC DRUGS.

By reducing activity in the neural pathways of the brain that use dopamine as the neuritransmitter, these drugs elimate symptoms such as hallucinations.

The fact that these drugs alleviate many symptoms of schizophrenia stretched the case for the important role of dopamine in this disorder.

The Revised Dopamine Hypothesis.

Davis and Kahn 1991

They proposed that the postive symptoms of schizophrenia are caused by an excess of dopamine in sub cortical areas of the brain, partially in the Mesolithic pathway.

Neural imaging

Patel et al 2010

  • By using PET scans to asses dopamine levels in schizophrenia and normal individuals.
  • Found lower levels of dopamine in the dorsolateral prefrontal cortex of schizophrenic patients compared to normal patients.

Animal studies

Wang and Deutch 2008

  • They induced dopamine depletion in the prefrontal cortex in rats.
  • Found that you could reverse cognitive impairments using olanzapinem an atypical antipsychotic drug.

Ague the reductionist issues with this study.