Biological Explanations for Schizophrenia [AQA ALevel]

Summary

This video explores the biological explanation of schizophrenia, focusing on genetics, neural structures, and neurotransmitters. It highlights how schizophrenia is polygenic, with multiple genes increasing risk, and reviews studies showing genetic links through family, twin, and adoption studies. The video also discusses neural correlates like the dopamine hypothesis and enlarged brain ventricles. Lastly, it evaluates the deterministic and reductionist views, contrasting biological explanations with the diathesis-stress model, which integrates genetic and environmental factors in the development of schizophrenia.

Takeaways

• 🧬 Schizophrenia has a biological basis, involving physical processes such as genetics and neurotransmitter activity, especially dopamine.
• 🔬 Schizophrenia is polygenic, meaning multiple genes increase the risk, with over 108 gene loci identified in studies like Ripke's.
• 👨‍👩‍👧‍👦 Family and twin studies, including Gottesman's research, suggest a genetic link, with higher concordance rates in identical twins (48%) compared to non-identical twins (17%).
• 📊 Aetiological heterogeneity means that different gene combinations cause schizophrenia in different individuals.
• 👶 Adoption studies show that biological risk for schizophrenia can be influenced by the environment, as seen in Tienari's research.
• 🧠 Neural correlates, such as hyperdopaminergia and hypodopaminergia, are linked to symptoms of schizophrenia like hallucinations and avolition.
• 💊 The dopamine hypothesis is supported by the effectiveness of antipsychotic drugs, which reduce dopamine and alleviate symptoms.
• 🔎 Enlarged ventricles in the brain have been observed in people with schizophrenia, but it's unclear if this is a cause, effect, or side effect of medication.
• ⚖️ Determinism vs. free will: The biological explanation of schizophrenia suggests it is inevitable, but cognitive perspectives allow for potential control over thought processes.
• 🌍 A more holistic approach, the diathesis-stress model, combines genetic predisposition with environmental triggers like family dysfunction to explain schizophrenia.

Q & A

What does it mean to say schizophrenia has a biological cause?

Saying schizophrenia has a biological cause implies that the disorder arises from physical processes in the body, particularly involving genetic factors, neural structures, and neurotransmitter activity.

Is there a single gene responsible for schizophrenia?

No, there is no single gene responsible for schizophrenia. It is polygenic, meaning that multiple genes contribute to the risk of developing the disorder.

What did Ripke's research on schizophrenia genetics discover?

Ripke's research, which studied over 36,000 individuals with schizophrenia, identified 108 gene loci associated with the condition. Many of these genes are linked to the nervous and immune systems.

What is meant by schizophrenia being 'aetiologically heterogeneous'?

'Aetiologically heterogeneous' means that schizophrenia can arise from different combinations of genes, causing variations in how the disorder develops in different individuals.

How do family and twin studies support the genetic basis of schizophrenia?

Family and twin studies show that schizophrenia is more common in close relatives of those with the disorder. For example, research by Gottesman found a 48% concordance rate in identical twins and a 17% rate in non-identical twins, suggesting a genetic component.

Why doesn't the concordance rate for identical twins reach 100% in schizophrenia studies?

Although identical twins share the same DNA, the concordance rate for schizophrenia is only 48%, which suggests that environmental factors also play a significant role in the development of the disorder.

How do adoption studies provide insight into the genetic basis of schizophrenia?

Adoption studies, such as those by Tienari, show that children of schizophrenic mothers raised in healthy environments had a lower chance of developing schizophrenia (5.8%) compared to those raised in dysfunctional families (36.8%). This suggests both genetic and environmental factors influence the disorder.

What is the dopamine hypothesis of schizophrenia?

The dopamine hypothesis suggests that an imbalance or excess of dopamine in certain areas of the brain, such as Broca's area, contributes to positive symptoms like hallucinations, while low dopamine levels in areas like the frontal cortex may lead to negative symptoms.

What role do other neurotransmitters like glutamate and serotonin play in schizophrenia?

In addition to dopamine, lower levels of glutamate, which regulates learning and memory, and the involvement of serotonin, particularly through treatments like clozapine, are also implicated in the development of schizophrenia.

What does research about enlarged ventricles in the brains of people with schizophrenia suggest?

Research by Johnstone in the 1970s showed that people with schizophrenia tend to have larger brain ventricles, but this finding is correlational, and it is unclear if enlarged ventricles cause schizophrenia, result from it, or are a side effect of medication.

What is the difference between determinism and reductionism in the context of schizophrenia's biological explanation?

Determinism suggests that schizophrenia is inevitable if one has the genetic predisposition, while reductionism focuses on simplifying the disorder to basic biological processes, ignoring psychological factors. Holism, in contrast, acknowledges both genetic and environmental causes.