Assessment and diagnosis

A diagnosis of schizophrenia is not a simple one, with symptoms varying across individuals. This category contains information about diagnostic tools for schizophrenia and related disorders, and early detection tools for identifying those at risk of a first episode of psychosis.

Early detection

What is early detection of psychosis? Early detection refers to the correct identification of individuals who are at high risk of developing schizophrenia, with an emphasis on the development of frank psychosis. Several assessment tools have been constructed to effectively identify such individuals. Sensitivity of an assessment tool refers to the proportion of people who develop psychosis that were previously identified by the assessment tool as being at high risk. Specificity is the proportion of people who do not develop psychosis that were previously identified as not being at high risk. Assessment tools therefore aim to have both high sensitivity…

Outcome assessment tools

How can outcome assessment tools be used? Standardised assessment tools are vital for assessing a range of variables including symptoms, functioning and quality of life. The quality of these tools can be measured in various ways. ‘Reliability’ refers to the reproducibility of an instrument’s results across different assessors, settings and times. ‘Construct validity’ is the extent to which an instrument measures the theoretical construct it was designed to measure. This involves ‘convergent validity’ (the degree of correlation between different scales measuring the same construct); and ‘divergent validity’ (the lack of correlation between scales measuring different constructs). ‘Known groups’ validity’ is…

Schizoaffective disorder

What is schizoaffective disorder?  Schizoaffective disorder is on the schizophrenia spectrum of illnesses. Diagnosis of schizoaffective disorder requires schizophrenia-like symptoms of psychosis, in addition to affective/mood symptoms such as depression. There is some debate as to whether schizoaffective disorder represents a unique diagnosis or an intermediary between schizophrenia and mood disorders. There are also considerable differences between different diagnostic criteria regarding the definition of schizoaffective disorder; particularly the Diagnostic and Statistical Manual (DSM) and the International Classification of Diseases (ICD) criteria. Specifically, the ICD and also the Research Diagnostic Criteria (RDC) require simultaneous and equally prominent presence of psychotic and…

Schizophrenia

How is schizophrenia diagnosed?  Diagnostic scales are widely used within clinical practice and research settings. These scales have been extensively validated and provide a set of criteria that is used to define and diagnose an illness. Two key examples include the American Psychiatric Association’s Diagnostic and Statistical Manual (DSM) and the World Health Organization’s International Classification of Diseases (ICD). Both the DSM and ICD criteria are regularly updated, and the most recent versions are the DSM-5 and the ICD-10. For a DSM-5 diagnosis of schizophrenia, at least two symptoms need to have been present for at least six months, and…

Schizophreniform disorder

What is schizophreniform disorder? Schizophreniform disorder is a part of the schizophrenia spectrum of disorders and has sometimes been used as a provisional diagnosis while waiting to see if symptoms improve by six months or progress, resulting in a diagnosis of schizophrenia. DSM-5 requires at least one of the following symptoms is present for a significant portion of the time during a one-month period, but for less than six months: delusions, hallucinations or disorganised speech. Disorganised behaviour (e.g. catatonia) or negative symptoms (e.g. social withdrawal) may also be present. There can be no manic, depressive or mixed manic-depressive episodes, and…

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