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Issues of reliability
Reliability refers to the consistency of a measuring instrument, such as a scale, to assess, for
example the severity of schizophrenic symptoms.
Reliability can be measured in terms of whether two independent assessors give similar
diagnoses (inter-rater reliability) or whether tests used to deliver these diagnosis' are consistent
over time (test-retest reliability).
The publication of DSM-III was specifically designed to provide a much more reliable system for
classifying psychiatric disorder, hoping to fix the problem of inter-rater reliability. However there
is little evidence that DSM is routinely used with high reliability by mental health clinicians.
Whaley (2001)- inter-rater reliability correlation in the diagnosis of schizophrenia is as low as +11.
Further problems of inter-rater reliability are highlighted by Rosenhan study- on being sane in
insane places- normal people presented themselves to psychiatric hospitals claiming they heard
an unfamiliar voice in their head. They were all diagnosed with schizophrenia and admitted,
throughout the stay non of the staff recognized them as normal.
When 50 senior psychiatrists in the US were asked to differentiate between `bizarre' and `non-
bizarre delusions', they produced inter-rater reliability correlations of only +40, forcing the
researcher to conclude that even this central diagnostic lacks sufficient reliability for its to be a
reliable method of distinguishing between schizophrenic and non-schizophrenic patients.
Cheniaux et al (2009)- investigated inter-rater reliability of the diagnosis of schizophrenia
according to both DSM-IV and ICD-10, although inter-rater reliability above 50+, schizophrenia
was more frequently diagnosed according to ICD-10.
Reliability of the diagnosis of schizophrenia is further challenged by findings that there are
massive variations between countries. Copeland gave 134 US and 194 British psychiatrists
description of a patient. 69% of US diagnosed schizophrenia compared with only 2% in the UK.…read more
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Issues of Validity
Validity refers to what extent the diagnosis represents something that is real and
distinct from other disorders and the extent that a classification system measures
what it claims to measure.
Comorbidity is an important issue for validity of diagnosis of mental illness. It refers to
the extent that two or more condition co-occur. Psychiatric comorbidities are common
among patients with schizophrenia. These include substance abuse, anxiety and
symptoms of depression. A study estimates that comorbid depression occurs in 50% of
patients. Such comorbidity makes it difficult to diagnose the disorder and also what
treatment to use. The poor level of functioning found in many schizophrenics may be
less the result of their psychiatric disorder and more to do with untreated comorbid
physical disorders. US study by Weber et al examined nearly 6 million hospital
discharge records to calculate comorbidity. Psychiatric and behavior related diagnoses
accounted for 45% of comorbidity.
Despite the belief that identification of symptoms would make for a more valid
diagnosis, many of these symptoms are found in many other disorders, such as
depression and bipolar. Ellason and ross point out that people with DID (dissociative
identity disorder) actually have more schizophrenic symptoms that people diagnosed
with schizophrenia! Supported by Schneider who found many first rank symptoms
were also characterized in other disorders e.g. bipolar.
People with schizophrenia rarely share the same symptoms, nor is there evidence that
they share the same outcome. The prognosis for patients vary. A diagnosis of
schizophrenia therefore has little predictive validity.…read more
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Biological explanation- Genetics
Family studies (Gottesman) have established that schizophrenia is more common among biological
relatives of a person with schizophrenia, and that the closer the degree of genetic relatedness the
greater the risk. Kendler has shown that first degree relatives of those with schizophrenia are 18x
more at risk than the general population.
Twin studies offer an alternative way of establishing genetic links, by comparing the differences in
concordance rates. Both share the same environment, but only MZ twins have identical make up.
Many studies have been conducted and they all show a much higher concordance rate in MZ twins
compared with DZ. To separate genetics conclusively from the environment, researchers have sort
out MZ twins reared apart where one twin has been diagnosed with schizophrenia. Gottesman and
Shields used the Maudsley twin register and found 58% were concordant with schizophrenia (7 out of
12 MZ twins reared apart).
Adoption studies are a more effective way of separating out the effects of environmental and genetic
factors. A Danish adoption study by Kety et al, taking a national sample from across Denmark, found
high rates of diagnosis for chronic schizophrenia in adoptees who biological parents had the same
diagnosis, even though they had been adopted by `healthy' parents. Indicated a strong genetic link.
Methodological problems with studies, they are all retrospective and diagnosis may be biased by
knowledge that other family members have been diagnosed, suggesting a problem with demand
Difficult to separate the effects of nature v nurture. The fact concordance rates are not 100% means
that it cannot fully be explained by genes and it could be that an individual has a predisposition to
schizophrenia which simply makes the individual more at risk. A biological account cannot give a full
explanation of the disorder.
Family studies lack population validity because samples that are used are small in number and only a
select number of families are used. Suggests there are issues with it being generalized to the whole
target population.…read more
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Biological explanations-the dopamine hypothesis
Dopamine is one of the many different neurotransmitters that operate in the brain. The dopamine
hypothesis states that messages from neurons that transmit dopamine fire too easily or too often,
this overload leads to the characteristic symptoms of schizophrenia. Evidence for this comes from
amphetamines, a dopamine agonist. Large doses of amphetamines given to people with no history
of psychological disorders produces behavior which is similar to paranoid schizophrenia. Small doses
given to people who already have schizophrenia tend to worsen their symptoms.
Further evidence to connect dopamine and schizophrenia comes from antipsychotic drugs, which act
as dopamine antagonists. They work by blocking the activity of dopamine in the brain. By reducing
stimulation of the dopamine system, these drugs help to eliminate/alleviate symptoms.
Low levels of dopamine activity are found in people who suffer from Parkinson's disease, a
degenerative neurological disorder. It was found that some people taking the drug L-dopa to raise
their levels of dopamine were developing schizophrenic symptoms (Grilly, 2002).
One strength of the research into schizophrenia is that is has practical application and has led to the
development of new drugs which are more effective.
One problem of the dopamine hypothesis is there is a problem with the chicken egg dilemma. Is it
raised dopamine levels that cause schizophrenia, or are raised dopamine levels the result of
schizophrenia. This suggests what needs to be careful is establishing cause and effect.
Contradictory evidence as new drugs which have been proven to be effective, despite blocking fewer
Biologically determinist, if an individual does have excessive amounts of dopamine then does it
really mean they will develop schizophrenia? Dopamine hypothesis does not account for freewill.
Neuroimaging studies have, as yet, failed to provide convincing evidence of altered dopamine
activity in the brains of individuals with schizophrenia.…read more
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Freud believed that schizophrenia was the result of two related processes in the sub-conscious,
regression to a pre-ego stage and attempts to re-establish ego control. If the world of the schizophrenic
has been particularly harsh, for example cold and uncaring parents, an individual may regress to this early
stage in their development before the ego was properly formed and before he or she had developed a
realistic awareness of the external world. Schizophrenia was thus seen by Freud as an infantile state, with
some symptoms (delusions of grandeur) reflecting this primitive condition and other symptoms
(hallucinations)reflecting the person's attempt to re-establish ego control.
There are several family variables which are thought to contribute to the formation of schizophrenia:
Schizophrenogenic mother- actions that are often contradictory, verbally accepting yet behaviorally
rejecting, this can set up faulty communication between mother and child and can lead to the onset of
The double-blind theory- children who frequently receive contradictory messages from the parent are
more likely to develop schizophrenia. For example a mother that tells the child she loves him, then turns
her head in disgust. The child's ability to respond to the mother is incapacitated as one message
invalidates the other. These interactions prevent the development of an internally coherent construction
of reality, manifesting into symptoms.
Expressed emotion- negative emotional climate that involves criticism, hostility and emotional over-
involvement. High levels of EE are more likely to influence relapse rate, patient returning to high EE 4x
more likely to relapse (Liszen et al). Negative emotional climate leads to stress beyond the patients
already impaired coping mechanism, thus triggering schizophrenic episode.
Schofield and Balian- 178 schizophrenic patients and 150 non-schizophrenics had their childhood
experiences compared to see whether schizophrenics really do have a more difficult childhood. In the
quality of relationships between parents there was no real difference found. However, there was a
significant difference in the quality of maternal relationship, patients mothers who are less likely to be
affectionate are more likely to be domineering and overprotective (schizophrenogenic mother)
One weakness is that is it deterministic. Suggests all thoughts, behaviours and emotions our determined
by our childhood experiences and unconscious mental processes. No conscious free will over our
It is also reductionist as reduces behaviour down to the mind, not taking account of environment or