Briefly describe + evaluate 1 bio exp of scz (10)

• Para 1: dopamine hypothesis

  • P: One biological explanation of schizophrenia is the dopamine hypothesis, which proposes that schizophrenia is caused by abnormal dopamine activity in the brain.

  • E: early versions of the hypothesis suggested a general overproduction of dopamine, supported by Griffith et al (1968) who found that non-schizophrenic volunteers given amphetamines (which increase dopamine) developed psychotic symptoms.

  • E: the revised hypothesis focuses on specific pathways: hyperactivity in the mesolimbic pathway is linked to positive symptoms like hallucinations, while hypoactivity in the mesocortical pathway - especially in the frontal lobe - is associated with negative and cognitive symptoms (Davis et al 1991).

  • L: Antipsychotic drugs that block dopamine receptors (especially D2) have been found to reduce symptoms, further supporting this explanation.
• Para 2: dopamine hypothesis

  • P: however, the dopamine hypothesis is incomplete and methodologically limited.

  • E: measuring dopamine directly is difficult, so researchers rely on its metabolite HVA in cerebrospinal fluid, which requires invasive lumbar punctures and is influenced by factors like diet and drug use - reducing reliability.

  • E: Furthermore, atypical antipsychotics like clozapine, which affect both dopamine and serotonin (5-HT2A) receptors, are more effective for many patients, suggesting other neurotransmitters are involved. • L: Additionally, it’s unclear whether dopamine abnormalities cause schizophrenia or are a consequence of it; PET scan studies (e.g. Copolov & Crook, 2000) have failed to consistently detect differences in dopamine activity between schizophrenic and non-schizophrenic individuals.
• Conclusion

  In conclusion, while the dopamine hypothesis has strong pharmacological and theoretical support, it cannot fully explain schizophrenia on its own. It is likely that multiple neurotransmitters, genes, and environmental factors interact to produce the disorder.