Classification of schizophrenia
● 1% of the population have schizophrenia. Onset of first symptoms is typically around 15
to 45 years of age. Men are more likely to get schizophrenia, typically having an earlier
onset.
● The Diagnostic and Statistical Manual (DSM) is most often used to diagnose
schizophrenia. However the ICD (International Classification of Disease) can also be
used. DSM-5 and ICD-10 are two separate systems/criteria for diagnosis.
o DSM-5 requires one positive symptom.
o ICD-10 requires two negative symptoms.
Positive symptoms of schizophrenia, including hallucinations and
delusions
★ Positive Symptoms: additional experiences that are beyond those of ordinary
existence. Examples include hallucinations (additional sensory experiences such as
seeing distortions in objects that look like faces, or hearing voices), and delusions
(irrational beliefs about themselves or the world, such as feelings of persecution or
grandeur).
Negative symptoms of schizophrenia, including speech poverty and avolition
★ Negative symptoms are losses of normal experiences and abilities. Examples are
Avolition (a lack of purposeful behaviour. No energy to socialise or look after hygiene.
Generally apathetic) and Speech Poverty (Brief verbal communication style. Loss of
quality and quantity of verbal responses. Can be classified as a positive symptom if
speech is excessively disorganised with sufferers wandering off the point).
Reliability and validity in diagnosis and classification of schizophrenia, including
reference to co-morbidity, culture and gender bias and symptom overlap
● Reliability is the extent to which a finding is consistent. It is the extent to which
psychiatrists can agree on the same diagnosis when independently assessing patients
(inter-rater reliability). In order for a classification system to be reliable, the same
diagnosis should be made each time. Therefore different psychiatrists should reach the
same decision when assessing a patient.
● Test-retest reliability is if the same thing measured under the same conditions yields the
same results every time, i.e: the same doctor giving the same diagnosis over time for the
same symptoms.
● Inter-rater reliability of schizophrenia diagnosis is often low. Beck (1963) found only a
54% concordance rate between doctors’ assessments of 153 patients.
● However Jakobsen et al. (2005) tested the reliability of the ICD-10 classification system
in diagnosing schizophrenia. A hundred Danish patients with a history of psychosis were
assessed using operational criteria, and a concordance rate of 98% was obtained. This
demonstrates the high reliability of the clinical diagnosis of schizophrenia using
up-to-date classification.
, ★ Validity is the extent to which we are measuring what we are intending to measure. In
the case of an illness like schizophrenia we have to consider the validity of the diagnostic
tools; for example, do different assessment systems arrive at the same diagnosis for the
same patient? Validity of schizophrenia is also the question as to whether or not it is a
unique disorder or not, meaning that (if it is) it has its own unique characteristics and
causes.
● One reason that the validity of schizophrenia as a condition is questioned is
comorbidity. Comorbidity is when a person has more than one mental condition.
Buckley (2009) found that 50% of schizophrenics are also diagnosed with depression,
47% with drug abuse, and 29% with PTSD, and 23% with OCD. So conditions like
severe depression could be being misdiagnosed as schizophrenia. Or, as these
diagnoses often happen together, perhaps they are not even separate disorders.
● Another issue with the validity of schizophrenia diagnosis is symptom overlap. Other
disorders like bipolar disorder have hallucinations and delusions as positive symptoms
as well. If two disorders are very similar then they may be the same disorder.
● Another issue with schizophrenia is gender bias. It may be that men are more likely to
be diagnosed due to gender bias as women’s issues aren’t taken as seriously. Cotton et
al (2009) suggests that women could just have better coping strategies and so don’t
access treatment as often as men. On the contrary Lewin (1984) found that the number
of female sufferers reduced when clearer diagnostic criteria were used, meaning that
clinicians were overdiagnosing women.
● The next issue is predictive validity. If diagnosis leads to successful treatment, the
diagnosis can be seen as valid. But in fact some Schizophrenics are successfully treated
whereas others are not. Heather (1976) there is only a 50% chance of predicting what
treatment a patient will receive based on diagnosis, suggesting that diagnosis is not
valid.
● Then there is aetiological validity – for a diagnosis to be valid, all patients diagnosed
as schizophrenic should have the same cause for their disorder. This is not the case with
schizophrenia: The causes may be one of biological or psychological or both.
● Finally, there is cultural bias in the diagnosis of schizophrenia. Cochrane (1977) found
that the rate of diagnosis of schizophrenia in the UK for afro-caribbean people was 7%,
compared to 1% for the general Uk population and 1% for afro-caribbeans in the
caribbean.This suggests that afro-caribbean people are overdiagnosed in the UK due to
culture bias. Fernando (1998) suggests ‘category failure’, that is that western definitions
applied to non-western cultures lead to a higher diagnosis rate in people from
non-Western cultures. In addition, Copeland et al. (1971) gave a description of a patient
to 134 US and 194 British psychiatrists. 69% of the US psychiatrists diagnosed
schizophrenia but only 2% of the British gave the diagnosis of schizophrenia. No
research has found any cause for this, so it suggests that the symptoms of ethnic
minorities are misinterpreted. This calls into question the reliability of the diagnosis of
schizophrenia as it suggests that patients can display the same symptoms but receive
● 1% of the population have schizophrenia. Onset of first symptoms is typically around 15
to 45 years of age. Men are more likely to get schizophrenia, typically having an earlier
onset.
● The Diagnostic and Statistical Manual (DSM) is most often used to diagnose
schizophrenia. However the ICD (International Classification of Disease) can also be
used. DSM-5 and ICD-10 are two separate systems/criteria for diagnosis.
o DSM-5 requires one positive symptom.
o ICD-10 requires two negative symptoms.
Positive symptoms of schizophrenia, including hallucinations and
delusions
★ Positive Symptoms: additional experiences that are beyond those of ordinary
existence. Examples include hallucinations (additional sensory experiences such as
seeing distortions in objects that look like faces, or hearing voices), and delusions
(irrational beliefs about themselves or the world, such as feelings of persecution or
grandeur).
Negative symptoms of schizophrenia, including speech poverty and avolition
★ Negative symptoms are losses of normal experiences and abilities. Examples are
Avolition (a lack of purposeful behaviour. No energy to socialise or look after hygiene.
Generally apathetic) and Speech Poverty (Brief verbal communication style. Loss of
quality and quantity of verbal responses. Can be classified as a positive symptom if
speech is excessively disorganised with sufferers wandering off the point).
Reliability and validity in diagnosis and classification of schizophrenia, including
reference to co-morbidity, culture and gender bias and symptom overlap
● Reliability is the extent to which a finding is consistent. It is the extent to which
psychiatrists can agree on the same diagnosis when independently assessing patients
(inter-rater reliability). In order for a classification system to be reliable, the same
diagnosis should be made each time. Therefore different psychiatrists should reach the
same decision when assessing a patient.
● Test-retest reliability is if the same thing measured under the same conditions yields the
same results every time, i.e: the same doctor giving the same diagnosis over time for the
same symptoms.
● Inter-rater reliability of schizophrenia diagnosis is often low. Beck (1963) found only a
54% concordance rate between doctors’ assessments of 153 patients.
● However Jakobsen et al. (2005) tested the reliability of the ICD-10 classification system
in diagnosing schizophrenia. A hundred Danish patients with a history of psychosis were
assessed using operational criteria, and a concordance rate of 98% was obtained. This
demonstrates the high reliability of the clinical diagnosis of schizophrenia using
up-to-date classification.
, ★ Validity is the extent to which we are measuring what we are intending to measure. In
the case of an illness like schizophrenia we have to consider the validity of the diagnostic
tools; for example, do different assessment systems arrive at the same diagnosis for the
same patient? Validity of schizophrenia is also the question as to whether or not it is a
unique disorder or not, meaning that (if it is) it has its own unique characteristics and
causes.
● One reason that the validity of schizophrenia as a condition is questioned is
comorbidity. Comorbidity is when a person has more than one mental condition.
Buckley (2009) found that 50% of schizophrenics are also diagnosed with depression,
47% with drug abuse, and 29% with PTSD, and 23% with OCD. So conditions like
severe depression could be being misdiagnosed as schizophrenia. Or, as these
diagnoses often happen together, perhaps they are not even separate disorders.
● Another issue with the validity of schizophrenia diagnosis is symptom overlap. Other
disorders like bipolar disorder have hallucinations and delusions as positive symptoms
as well. If two disorders are very similar then they may be the same disorder.
● Another issue with schizophrenia is gender bias. It may be that men are more likely to
be diagnosed due to gender bias as women’s issues aren’t taken as seriously. Cotton et
al (2009) suggests that women could just have better coping strategies and so don’t
access treatment as often as men. On the contrary Lewin (1984) found that the number
of female sufferers reduced when clearer diagnostic criteria were used, meaning that
clinicians were overdiagnosing women.
● The next issue is predictive validity. If diagnosis leads to successful treatment, the
diagnosis can be seen as valid. But in fact some Schizophrenics are successfully treated
whereas others are not. Heather (1976) there is only a 50% chance of predicting what
treatment a patient will receive based on diagnosis, suggesting that diagnosis is not
valid.
● Then there is aetiological validity – for a diagnosis to be valid, all patients diagnosed
as schizophrenic should have the same cause for their disorder. This is not the case with
schizophrenia: The causes may be one of biological or psychological or both.
● Finally, there is cultural bias in the diagnosis of schizophrenia. Cochrane (1977) found
that the rate of diagnosis of schizophrenia in the UK for afro-caribbean people was 7%,
compared to 1% for the general Uk population and 1% for afro-caribbeans in the
caribbean.This suggests that afro-caribbean people are overdiagnosed in the UK due to
culture bias. Fernando (1998) suggests ‘category failure’, that is that western definitions
applied to non-western cultures lead to a higher diagnosis rate in people from
non-Western cultures. In addition, Copeland et al. (1971) gave a description of a patient
to 134 US and 194 British psychiatrists. 69% of the US psychiatrists diagnosed
schizophrenia but only 2% of the British gave the diagnosis of schizophrenia. No
research has found any cause for this, so it suggests that the symptoms of ethnic
minorities are misinterpreted. This calls into question the reliability of the diagnosis of
schizophrenia as it suggests that patients can display the same symptoms but receive
