Describe

• Genetics and genetic vulnerability

  One biological explanation for schizophrenia
• Genes

  • Determine many elements of an individual based on phenotypes and genotypes
  • Phenotypes are the observable expression of inherited characteristics, such as: eye colour, and hair colour
  • Recent research has shown that there is a biological and genetic contribution to many different disorders both physical and mental
• Genetic predisposition

  Schizophrenia can be inherited through
• Gene

  • Discovered by researchers from MIT and Harvard
  • Known as complement component 4 (C4)
  • Referred to as a "schizophrenia risk gene"
  • Appears to be involved in eliminating connections between neurons (synaptic pruning) which happens naturally in teen years
  • May be why schizophrenia typically starts to "develop" or an individual will typically begin displaying symptoms in their adolescence
• Twin studies

  • Main way that the genetic links between schizophrenia have been researched
  • Identical twins (monozygotic "MZ" twins) have the same genes
  • Theoretically if genetic vulnerability is the only cause of schizophrenia, they would have a 100% concordance rate, meaning both twins would inherit the disorder
• Dopamine hypothesis

  Another biological explanation of schizophrenia
• Dopamine hypothesis

  • Proposes that individuals with schizophrenia have too much of the neurotransmitter dopamine
  • Demonstrated symptoms related to high levels of dopamine
  • Initial hypothesis was too simplistic as it did not account for individuals who experienced negative symptoms of schizophrenia
• Antipsychotic drugs

  • Impact D2 receptor sites
  • D2 receptor sites are primarily found in subcortical regions
  • Limbic system has been the main area of research
• Limbic system

  • Variety of subcortical structures that engage in many functions, mainly emotional regulation, memory and arousal
  • Nerve pathways leave from the limbic system to many other structures
  • Two main pathways linked to schizophrenia are the mesolimbic pathway and the mesocortical pathway
• Mesolimbic pathway

  • Dopamine is a major neurotransmitter
  • Too much dopamine, from neurones that fire too quickly or too often, cause overstimulation and are linked to the cause of positive symptoms of schizophrenia, I.e. hallucinations, delusions and disordered thinking
• Mesocortical pathway

  • Nerve pathway largely responsible for emotional regulation, motivation and cognition
  • If too little dopamine is present in the D2 receptors, this may be the reason for many cognitive impairments, otherwise known as negative symptoms (alogia, avolition, catatonia, flatness of affect, anhedonia) within an individual with schizophrenia