Slides in this set
Classification of SZ
About 1% of the population has Positive Negative
Symptoms of SZ are divided
into positive and negative Delusions Affective
symptoms. Positive Experiences of flattening
symptoms reflect an excess
or distortion of normal
functions. Negative Hallucinations Avolition
symptoms are those that Distorted Catatonic
appear to reflect a diminution
or loss of normal function. thinking Behaviour
The DSM-IV-TR, the diagnosis
of SZ requires at least 1
month of these symptoms.…read more
Evaluation of Classification
With regard to the DSM- III psychiatrists now have a reliable
classification system which has led to greater agreement over who
did or did not have SZ.
However, Whaley et al (2001) found inter-rater reliability correlations
to be low as 0.1.
Klosterkotter et al (1994) assessed 489 admissions to a psychiatric
ward in Germany. They found that positive symptoms were more
useful for diagnosis than negative symptoms. This raises problems as
individuals with different behaviours can have the same diagnosis of
Rosenhan (1973) normal people presented themselves in a
psychiatric hospital in the US claiming they heard unfamiliar voices
in their heads. They were all diagnosed with SZ and admitted. They
behaved normally throughout their stay. Staff didn't recognise that
they were actually normal. In a follow up study he warned hospitals
of his intention to send out more `pseudopatients'. 21% detection
rate but no patients were actually sent.…read more
Some of the Schizophrenic symptoms are actually found in many other
disorders such as depression and bipolar. This means that patients may
not get the right diagnosis which could lead to the wrong treatment
therefore their condition could become worse.
Scheff (1966) believed that `labelling' someone with a psychotic disorder
could lead to self fulfilling prophecy.
Diagnosis has little predictive validity whereby some people never appear
to recover from the disorder. Evidence suggests that it is more to do with
gender and psychosocial factors such as social skills and family tolerance.
(Harrison et al , 2001).
Cultural differences Copland et al gave a description of a patient to US
and UK psychiatrists. 69% of US diagnosed with SZ but only 2% of UK
gave the same diagnosis. This may be due to DSM being developed in
America and the ICD being developed in Europe. This makes it difficult
for conclusions to be made from research if they use different criteria.
There is now evidence that early diagnosis and prompt assignment to
treatment is associated with a better long term outcome for people with
SZ (Jackson and Birchwood, 1996)
Individual differences have led people to suggest that SZ is not a single
disorder and various sub-types have been suggested. But the validity of
these sub-types have been questioned. Other symptoms have develop
later. Sub-types are only used in minority of cases where there is close
correspondence to the criteria.…read more
Family Gottesman, such studies have found that SZ is more common among biological
relatives of a person with SZ, and that the closer the degree of genetic relatedness, the
greater the risk. E.g. children with two SZ parents have a concordance rate of 46%.
With one parent 13% and siblings 9%.
However, many researchers note that these concordance rates may be due to common
rearing patterns and other factors that are not heredity.
Twins Joseph (2004) found a concordance rate for MZ twins (identical) of 40.4% and
for DZ twins (non-identical) 7.4%.
Similar studies which have used `blind diagnosis' and found lower concordance rates
for MZ twins. Also twin studies do not use the same diagnostic criteria.
But there is still evidence for genetics as the concordance rate for MZ twins is still
much higher than DZ twins
MZ twins are relatively rare in the population and of these only 1% would be expected
to have SZ so sample size is always small.
Concordance rates can be calculated in different ways and vary depending on the
method used.…read more
Adoption Kety (1994) found high rates of SZ in individuals whose biological parents had the
disorder but who have been adopted by psychologically healthy parents.
Tienari et al (2000) in Finland, 164 adoptees whose biological mothers had been diagnosed with
SZ 6.7 % received a diagnosis of SZ compared to 2% of controlled adoptees (non SZ
These %s are still low showing that other factors may cause SZ. Methods such as the
diathesis stress model would be better to explain SZ, combines biological factors with
States that messages from the neurons that transmit dopamine fire too easily leading to SZ
symptoms. SZ are thought to have abnormally high numbers of D2 receptors resulting in
more dopamine binding and so more neurons firing.
Phenothiazines block dopamine at the synapse are effective in alleviating positive symptoms
Patients with Parkinson's disease are thought to have low levels of dopamine. L-dopa is
used to raise their levels of dopamine and it can produce symptoms of SZ in previously
Post Mortems of people with SZ have shown an increase in dopamine levels. Seeman
reviewed a number of studies which found increases in dopamine receptor density between
60 110 % compared to controls.
PET scans- Wong et al found a two fold increase in the density of dopamine receptor sites
in SZ patients who have never been treated with drugs compared to patients who had been
and to a control.
Dopamine hypothesis is over simplified.
Later PET studies have not replicated Wong's results
L-dopa does not worsen symptoms is everyone
Phenothiazines do not work for everyone diagnosed with SZ. They only alleviate positive
symptoms However, there are different types of DZ and these might have different
underlying causes.…read more