schizophrenia

• schizophrenia is a chronic mental illness that makes people lose touch with reality
• DSM-5 classifies scz when a person experiences two positive or negative symptoms
• ICD-10 classifies scz when a person experiences two or more negative symptoms
• positive symptoms of scz causes distress to both the patient and the other people as they are actively manifesting their illness
• positive symptoms include

  • hallucinations
  • delusions: formed from irrational beliefs or paranoia
• negative symptoms of scz is described as a withdrawal from life, the symptoms are very similar to depression
• negative symptoms include

  • speech disorganisation
  • avolition: complete lack of motivation about their lives
• inter-rater reliability refers to consistency and agreement across diagnosing clinicians
• validity of the diagnosis refers to the 'realness' of what is being measured
• research investigating into reliability and validity

  • meta-analysis of 25 studies with patients diagnosed by different clinicians and found that reliability of scz had lower inter-rater reliability than depression
  • validity of scz was tested in a field experiment in which he and eight confederates reported false symptoms and were all admitted to a mental hospital
• co-morbidity is when a patient present symptoms of more than one mental illness
• patients with scz are at an increased risk for the development of depression as the 2 illnesses may share a common genetic basis
• symptom overlap is when two or more illnesses present with some of the same symptoms
• research which investigated co-morbidity and symptom overlap

  • meta-analysis of DSM-5 diagnostic criteria does not sufficiently distinguish between scz symptoms and those of co-morbid disorders
  • sca has the following co-morbidities, 50% for depression, 29% for PTSD, 23% for OCD
• gender bias in diagnosis refers to any instances of a person being diagnosed according to their gender opposed to the set of symptoms they present with
• gender bias can also occur when a clinician does not take into account when making a diagnosis such as male models of health used to diagnose a women
• culture bias in diagnosis refers to any instances of a person being diagnosed according to their culture as opposed to the set of symptoms they present with
• culture bias may also occur when a clinician does not take a patients culture into account when making a diagnosis , western biomedical model is used to diagnose people from non-western culture
• research which investigates gender and culture bias in diagnosis

  • found that males and females are equally at risk of developing scz but scz is underdiagnosed in women
  • found that evidence that African Americans are 2.4 times more likely to be diagnosed with scz compared with white individuals
• genetic heritance refers to the extent to which a condition has been passed on generationally through families via genes
• research support: heritability of scz and found a concordance rate of 48% for scz between MZ
• there is no single gene that has been identified as causing scz rather a combination of several genes
• the genes which may increase a person's risk of developing scz are known as candidate genes and as there are several of them scz is referred to as polygenic
• research which investigates the genetic basis of scz

  • analysis of genomes of people found that the strongest known genetic risk for scz comes from the gene known as C4
  • meta-analysis found strong evidence for the heritability of scz and that specific candidate genes in combo with each other result in increased vulnerability to scz
• evaluation of genetic basis of scz

  strengths

  • methods used to measure a genetic explanation for scz is clinical and objective so they have good reliability and validity
  • huge body of research evidence which points to genetics playing a key role in scz

  weakness

  • genetic is a part of an explanation, if scz was purely genetics concordance rate in MZ twins must be 100%
  • symptoms of scz are varied and is different for each person, absence of a biomaker means that it is difficult to know if a patient has scz
• neural correlates of scz refers to the specific brain region that is related to the behaviour and symptoms of scz
• ventral striatum which is the largest structure in basal ganglia is associated with the negative symptoms
• scz patients show less activity in the ventral striatum which is associated with apathy
• the superior temporal gyrus is thought to be associated with processing speech, so the positive symptoms
• scz patients show reduced volume of grey matter in superior temporal gyrus
• dopamine hypothesis suggests that an overstimulation of dopamine receptors may be a contributory factor to developing scz
• original version suggests that hyperdopaminergia in the sub-cortex of the brain may be responsible for scz
• hyperdopaminergia assumes that an excess of dopamine in the central areas of the brain can alter perceptions of the world
• original theory is supported by research using dopamine antagonists which blocks dopamine pathways linked to a reduction in positive symptoms
• newer version of hypodopaminergia assumes that low levels of dopamine in the prefrontal cortex may lead to scz
• prefrontal cortex is responsible for logical thinking, therefore negative symptoms of scz such as speech poverty may be due to hypodopaminegia
• research which investigates neural correlated of scz

  • antipsychotic drugs that act as dopamine antagonists reduced positive symptoms
  • low levels of activity in the ventral striatum may be associated with the negative symptoms of avolition
• evaluation of neural correlates of scz

  strengths

  • brain imaging techniques such as MRIs provided objective evidence for neural correlates of scz as they pinpoint brain regions
  • the brain-imaging techniques are conducted under controlled clinical conditions hence they are reliable

  weakness

  • lacks cause and effect explanation as neural correlates takes a correlational approach to mapping brain regions
  • no acknowledgement of the role of the environment to neural correlates explanation lacks external validity
• typical antipsychotics are dopamine antagonists and are also known as first generation. they typically work well with positive symptoms by blocking dopamine receptors in the synapse. typical antipsychotics such as chloropromazine comes with side effects, one which may lead to tardive dyskinesia
• atypical antipsychotics were introduced to help overcome the side-effects of typical antipsychotics. they typically work with negative and positive symptoms. clozapine is one example of atypical antipsychotics which is prescribed when others don't work. it can also help with regulating mood as it also acts on seretonin receptors