How is a PTSD diagnosis made?

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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Last updated at: 2:03 am, 7th October 2021
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