Classifying and Diagnosing Schizophrenia
VALIDITY AND RELIABILITY
Validity - Refers to how accurately something is measured.
Reliability - Refers to how consistent something is.
DIAGNOSING AND CLASSIFICATION
Diagnosing - completed by a trained professional. To diagnose a disorder is to identify an illness
through the presentation of symptoms.
Classification - in this context, classification refers to how schizophrenia is clarified in diagnostic
manuals (DSM, ICD etc). A classification outlines what symptoms should be expected with each
disorder.
COMORBIDITY
This term refers to the concept that two or more conditions occur together in the same person at the
same time.
Buckley (2009) found comorbidity rates of schizophrenia and depression (50%), post-traumatic stress
disorder (29%) and OCD (23%).
Additionally, substance abuse was also found to be high (47%)
CULTURAL BIAS IN THE DIAGNOSIS OF SCHIZOPHRENIA
Cochrane (1977) reported that the incidence of schizophrenia in the West Indies and Britain to be
similar at around 1 percent. However, Afro-Caribbean men are several times more likely to be
diagnosed with schizophrenia when living in Britain.
GENDER BIAS IN THE DIAGNOSIS OF SCHIZOPHRENIA
Longnecker et al (2010) reviewed studies of the incidences of schizophrenia and concluded that since
the 1980s males have been diagnosed with schizophrenia more often than women. Prior to the 1980s
this was not the case.
SYMPTOM OVERLAP
Given that schizophrenia could be argued as an amalgamation of other disorders, the reliability and
validity of clinicians diagnosing schizophrenia should also be questioned. Symptom overlap reduces
the validity of diagnoses.
SYMPTOM OVERLAP FOR SCHIZOPHRENIA AND BIPOLAR
The positive symptoms of schizophrenia can look like the symptoms in about 50% of manic episodes,
especially those with psychotic features. These can include delusions of grandeur, hallucinations,
disorganised speech, paranoia, etc. The negative symptoms of schizophrenia can closely resemble
the symptoms of a depressive episode. These include apathy, extreme emotional withdrawal, lack of
affect, low energy, social isolation, etc.
Genetic Evidence - Wray et al (2013) report that both illnesses are linked to a variation at four
chromosomal sites. They found that the overlap in heritability attributable to common genetic variation
was about 15 percent between schizophrenia and bipolar disorder, about 9 percent between
schizophrenia and depression, and about 3 percent between schizophrenia and autism
Neurochemical Evidence - the two disorders share abnormalities in some of the same
neurotransmitter systems. For example, both depressive episode symptoms and the negative
symptoms of schizophrenia are at least partially mediated by serotonin. Likewise, the positive
symptoms of schizophrenia and the symptoms of mania are mediated in some way by excesses of
dopamine signalling. The atypical antipsychotics approved for both these disorders work on both the
serotonin and the dopamine systems
VALIDITY AND RELIABILITY
Validity - Refers to how accurately something is measured.
Reliability - Refers to how consistent something is.
DIAGNOSING AND CLASSIFICATION
Diagnosing - completed by a trained professional. To diagnose a disorder is to identify an illness
through the presentation of symptoms.
Classification - in this context, classification refers to how schizophrenia is clarified in diagnostic
manuals (DSM, ICD etc). A classification outlines what symptoms should be expected with each
disorder.
COMORBIDITY
This term refers to the concept that two or more conditions occur together in the same person at the
same time.
Buckley (2009) found comorbidity rates of schizophrenia and depression (50%), post-traumatic stress
disorder (29%) and OCD (23%).
Additionally, substance abuse was also found to be high (47%)
CULTURAL BIAS IN THE DIAGNOSIS OF SCHIZOPHRENIA
Cochrane (1977) reported that the incidence of schizophrenia in the West Indies and Britain to be
similar at around 1 percent. However, Afro-Caribbean men are several times more likely to be
diagnosed with schizophrenia when living in Britain.
GENDER BIAS IN THE DIAGNOSIS OF SCHIZOPHRENIA
Longnecker et al (2010) reviewed studies of the incidences of schizophrenia and concluded that since
the 1980s males have been diagnosed with schizophrenia more often than women. Prior to the 1980s
this was not the case.
SYMPTOM OVERLAP
Given that schizophrenia could be argued as an amalgamation of other disorders, the reliability and
validity of clinicians diagnosing schizophrenia should also be questioned. Symptom overlap reduces
the validity of diagnoses.
SYMPTOM OVERLAP FOR SCHIZOPHRENIA AND BIPOLAR
The positive symptoms of schizophrenia can look like the symptoms in about 50% of manic episodes,
especially those with psychotic features. These can include delusions of grandeur, hallucinations,
disorganised speech, paranoia, etc. The negative symptoms of schizophrenia can closely resemble
the symptoms of a depressive episode. These include apathy, extreme emotional withdrawal, lack of
affect, low energy, social isolation, etc.
Genetic Evidence - Wray et al (2013) report that both illnesses are linked to a variation at four
chromosomal sites. They found that the overlap in heritability attributable to common genetic variation
was about 15 percent between schizophrenia and bipolar disorder, about 9 percent between
schizophrenia and depression, and about 3 percent between schizophrenia and autism
Neurochemical Evidence - the two disorders share abnormalities in some of the same
neurotransmitter systems. For example, both depressive episode symptoms and the negative
symptoms of schizophrenia are at least partially mediated by serotonin. Likewise, the positive
symptoms of schizophrenia and the symptoms of mania are mediated in some way by excesses of
dopamine signalling. The atypical antipsychotics approved for both these disorders work on both the
serotonin and the dopamine systems
