A PTSD diagnosis requires exposure to at least one trauma. Traumas include being exposed to threatened death, actual or threatened serious injury, or actual or threatened sexual violence. Examples are direct exposure, witnessing a trauma, or learning that a relative or close friend was exposed.

At least one “intrusion” symptom is required for a PTSD diagnosis. These symptoms include unwanted and upsetting memories, nightmares, flashbacks, and emotional distress or physical reactions following reminders. At least one “avoidance” symptom is also required for a PTSD diagnosis. These symptoms include avoidance of trauma-related thoughts or feelings, and/or avoidance of trauma-related reminders. At least two “negative alterations in cognitions and mood” are required. These include negative thoughts or feelings that began or worsened after the trauma, an inability to recall key features of the trauma, overly negative thoughts and assumptions about oneself or the world, exaggerated blame of self or others for causing the trauma, negative mood, decreased interest in activities, feeling isolated, and difficulty experiencing positive mood. Finally, there needs to be at least two “hyperarousal” symptoms, such as irritability or aggression, risky or destructive behaviour, hypervigilance, heightened startle reaction, difficulty concentrating, and difficulty sleeping.

Symptoms must last for more than one month and cause significant distress or problems to the individual’s daily functioning. Symptoms must not be due to medication, substance use, or other illness. The latest World Health Organization’s International Classification of Diseases (ICD-11) also includes complex PTSD, which involves the core symptoms of PTSD plus disturbances in self organisation, mood dysregulation, negative self-concept, and disturbances in relationships.

A variety of tools have been developed to screen for or diagnose PTSD. The gold standards for diagnosis are the Clinician-Administered PTSD Scale (CAPS) and the Structured Clinical Interview for DSM-V (SCID-5), PTSD module. There are also a wide range of self-report PTSD measures, including the Primary Care PTSD Screen (PC-PTSD) and the PTSD Checklist (PCL), which are mostly used to monitor PTSD symptom severity, but can also be used for screening and diagnosing PTSD in people who have been exposed to trauma.

What is the evidence regarding diagnosis and detection of PTSD?

Moderate to high quality evidence finds a small increase in the severity of PTSD symptoms in people exposed to DSM-5 nominated traumas of actual or threatened death or serious injury or of threat to the physical integrity of self or others compared to people exposed to other traumas such as divorce, financial stress, or minor car accidents.

Around 24.5% of people diagnosed with PTSD have a delayed onset (>6 months post trauma), with most of these people experiencing earlier and milder subclinical symptoms. Delayed-onset PTSD is highest in professional groups and in those who experienced combat trauma (prevalence in both is around 40%).

There is reasonable sensitivity and good specificity of the PC-PTSD and the PCL for predicting a diagnosis of PTSD. There is good diagnostic validity and internal consistency, and reasonable test-retest and external (convergent) validity of the PCL. For children, the average T score on the Trauma Symptom Checklist for Children is around 50 in those exposed to traumatic events, which is 15 points less than the clinical cut-off for PTSD on this scale. Factors associated with increased scores on the Trauma Symptom Checklist for Children include international (vs. U.S.) samples, sexual abuse (vs. neglect, community violence, or complex trauma), female sex, and older age in sexual abuse samples.

Moderate to low quality evidence finds machine learning techniques (mostly support vector machine learning) using neuroimaging, neuropsychological, or audio data can reasonably predict PTSD in people previously diagnosed with PTSD using traditional means (mostly the CAPS or PCL).

August 2021

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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 affective symptoms; conversely, the DSM requires an additional period (>2 weeks) where the psychotic symptoms alone are present.

What is the evidence relating to schizoaffective disorder diagnosis?

Moderate to low quality evidence suggests schizoaffective disorder occupies an intermediary position between schizophrenia and mood disorders, but is not clearly distinct from either disorder.

Moderate quality evidence found people diagnosed with schizoaffective disorder using RDC/ICD criteria may have had fewer hospitalisations, are more likely to be male, and are more likely to be older or married than people diagnosed using DSM IIIR/IV criteria. Compared to people with schizophrenia, people with schizoaffective disorder may be more likely to be male, Caucasian, married, have a longer duration of illness, have lower levels of functioning, more depression, and more negative symptoms. Compared to people with bipolar disorder, people with schizoaffective disorder may be younger, have an earlier age at onset, fewer years of education, not Caucasian or African American, never married, have a longer duration of illness, more positive and negative symptoms, more depression, and higher IQ.

Around 36% of people initially diagnosed with schizoaffective disorder have their diagnosis changed at the second assessment. Conversely, around 55% of people diagnosed with schizoaffective disorder at the second assessment were originally diagnosed with other disorders. Schizophrenia or affective disorders were the most common original or subsequent diagnosis.

February 2022

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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-11.

For a DSM-5 diagnosis of schizophrenia, at least two symptoms need to have been present for at least six months, and for a significant portion of time over a one-month period. Symptoms include delusions, hallucinations, disorganised speech and behaviour, and negative symptoms such as diminished emotional expression, poverty of speech, and lack of purposeful action. At least one symptom of delusions, hallucinations, or disorganised speech needs to be present, and there also needs to be significant social or occupational dysfunction.

For an ICD-11 diagnosis of schizophrenia, at least two symptoms must be present, including positive, negative, depressive, manic, psychomotor, and cognitive symptoms. Of the two symptoms, one core symptom needs to be present, such as delusions, thought insertion, thought withdrawal, hallucinations, or thought disorder. Symptoms should have been present for most of the time during a period of at least one month.

What is the evidence on schizophrenia diagnosis?

Moderate to high quality evidence finds the DSM-III, DSM-III-R, and DSM-IV diagnostic criteria assigns more males with psychosis to schizophrenia than any other psychosis. Males are also found to have more negative symptoms. The ICD-9 shows no differences in gender distribution.

Moderate quality evidence finds Black people in the United States are more likely to be diagnosed with schizophrenia than White people in the United States. This is regardless of diagnostic method (structured vs. unstructured), or DSM version (DSM-III or DSM-IV). This effect was largest in studies with more males, more White patients, more young patients, studies in hospital or military settings, and studies conducted in the Midwest, Southeast, National, or multistate USA.

Moderate to high quality evidence suggests the proportion of first-episode psychosis patients retaining a diagnosis of schizophrenia over time is around 90%, and 72% for schizoaffective disorder. Also, the rate of a schizophrenia diagnosis following a diagnosis of schizophreniform disorder is around 65% over four years. Following brief, atypical, or not otherwise specified psychoses, the rate of a schizophrenia diagnosis is around 36% over four years. Following a substance-induced psychosis, the rate of a schizophrenia diagnosis is around 25% over four years. The rates of a transition to schizophrenia were highest for cannabis-induced psychosis, hallucinogen-induced psychosis, and amphetamine-induced psychosis.

Moderate to high quality evidence suggests better reliability for a diagnosis of schizophrenia than for a diagnosis of schizoaffective disorder. There was evidence to support vector machines combined with other machine learning techniques applied to structural and functional neuroimaging data (particularly prefrontal and temporal) for assisting the clinical diagnosis of schizophrenia.

February 2022

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