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How does a doctor diagnose PTSD?

Post-traumatic stress disorder (PTSD) is a complex psychiatric disorder that can develop after someone experiences or witnesses a traumatic event. PTSD can cause intense distress and severely impair daily functioning. Fortunately, doctors have effective tools to diagnose this condition.

What are the symptoms of PTSD?

There are four main types of PTSD symptoms:

  • Reliving the traumatic event through intrusive memories, flashbacks, or nightmares.
  • Avoiding reminders of the trauma through avoidance of certain people, places, activities, or emotions.
  • Negative changes in thinking and mood such as distorted thoughts about the cause of the event, negative emotions, decreased interest in activities, and feeling detached.
  • Increased arousal symptoms like being easily startled, feeling tense, having difficulty sleeping, and anger outbursts.

For a PTSD diagnosis, symptoms must last for at least one month and cause significant impairment in important areas of functioning. Symptoms usually begin within three months of the traumatic event but can sometimes take years to manifest.

How do doctors screen for PTSD?

The first step in diagnosing PTSD is screening patients who may be at risk. Doctors use screening tools to quickly assess whether symptoms of PTSD may be present. There are several validated screening instruments that doctors can use:

  • Primary Care PTSD Screen – A 4-item questionnaire that screens for the presence of PTSD symptoms.
  • PTSD Checklist for DSM-5 – A 20-item questionnaire that assesses for the presence and severity of PTSD symptoms.
  • Davidson Trauma Scale – A 17-item self-report measure that assesses PTSD symptom frequency and severity.

These screening tools cannot provide a diagnosis, but they can identify patients who need further assessment by a mental health professional.

What happens during a clinical interview?

If screening suggests possible PTSD, the next step is a comprehensive clinical interview conducted by a psychiatrist, psychologist, or other properly trained mental health provider. The goals of the interview are to:

  • Assess symptoms to determine if they meet PTSD criteria.
  • Identify any other co-occurring disorders that may be present.
  • Obtain a detailed trauma history.
  • Evaluate the patient’s functioning, quality of life, and suicide risk.

The provider asks questions to elicit details about the patient’s symptoms, trauma history, medical history, family history, social/occupational functioning, and current life circumstances. It is critical to create an environment where the patient feels comfortable sharing details relevant to making an accurate diagnosis.

What diagnostic criteria are assessed?

During the clinical interview, the doctor assesses the patient’s symptoms against standard diagnostic criteria for PTSD. The following criteria must be met for a PTSD diagnosis according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5):

Exposure to actual or threatened death, serious injury, or sexual violence through:

  • Directly experiencing the trauma
  • Witnessing the trauma occur to others
  • Learning that the traumatic event occurred to a close family member or friend
  • Experiencing repeated or extreme exposure to aversive details of the trauma (e.g., emergency responders)

Presence of at least 1 intrusion symptom such as:

  • Distressing memories or dreams about the trauma
  • Dissociative reactions like flashbacks where the event is relived
  • Intense distress when reminded of the trauma
  • Marked physical reactions when reminded of the trauma

Persistence avoidance of trauma-related stimuli after the event as evidenced by:

  • Avoiding thoughts, memories, feelings, or external reminders of the trauma
  • Inability to recall key features of the trauma

Negative alterations in cognitions and mood that began or worsened after the trauma seen through:

  • Inability to remember key aspects of the trauma
  • Exaggerated negative beliefs about oneself, others, or the world
  • Distorted cognitions leading to blame of self or others
  • Significantly negative emotional states like fear, horror, anger, guilt, or shame
  • Feeling alienated from others
  • Lack of interest in previously enjoyable activities
  • Inability to experience positive emotions

Trauma-related alterations in arousal and reactivity that began or worsened after the trauma, such as:

  • Irritability or aggression
  • Risky or destructive behavior
  • Hypervigilance
  • Heightened startle response
  • Difficulty concentrating
  • Difficulty sleeping

Duration of symptoms for more than 1 month

Significant impairment in different areas of functioning

Not attributed to medication, substance use, or other illness

The provider assesses for all of these criteria and ensures the symptoms represent a change from prior functioning that can be attributed to the traumatic event.

Are there any assessments or questionnaires used?

In addition to a clinical interview, doctors may use structured questionnaires or assessments to aid in diagnosing PTSD and determining symptom severity. Commonly used tools include:

  • Clinician-Administered PTSD Scale (CAPS-5) – Considered the gold standard for assessing PTSD. Has 30 items that evaluate PTSD diagnostic criteria.
  • PTSD Checklist for DSM-5 (PCL-5) – 20 self-report items mirror DSM-5 criteria. Helps quantify PTSD severity.
  • Posttraumatic Stress Disorder Symptom Scale (PSS) – 17-item scale assessing PTSD symptom frequency over the past two weeks.
  • Child PTSD Symptom Scale (CPSS) – Used to assess PTSD in children ages 8-18 years old.
  • Trauma Symptom Inventory (TSI) – 100 items evaluating posttraumatic stress and other psychological impacts of trauma.

These structured tools complement a clinical interview and can help determine areas of concern, track symptom changes over time, and indicate the need for further evaluation.

Could any other tests or assessments be used?

In addition to interviews and questionnaires, several other assessments may aid in diagnosing PTSD or identifying co-occurring conditions:

  • Physical exam – Rules out illness contributing to symptoms.
  • Laboratory testing – Helps exclude medical mimics or conditions that can worsen symptoms.
  • Psychological testing – Assesses personality, cognitive function, and other areas relevant to symptoms.
  • Sleep studies – Overnight polysomnograms can assess for sleep disorders worsening PTSD.

Brain imaging and genetic testing are not used clinically to make a PTSD diagnosis currently but are being studied for their ability to provide biological markers of the disorder.

How is PTSD differentiated from other disorders?

Since PTSD has overlapping symptoms with other mental health conditions, evaluating for disorders that could mimic or co-occur with PTSD is an important part of the diagnostic process. These include:

  • Other trauma/stressor-related disorders – Adjustment disorder, acute stress disorder
  • Depressive disorders – Major depressive disorder, persistent depressive disorder
  • Anxiety disorders – Generalized anxiety disorder, panic disorder
  • Obsessive-compulsive disorder
  • Sleep disorders – Insomnia, sleep apnea, nightmares
  • Substance use disorders
  • Personality disorders – Borderline, paranoid, avoidant
  • Neurocognitive disorders – Traumatic brain injury
  • Neurodevelopmental disorders – Autism spectrum disorder

A careful clinical interview assessing the timeline of symptoms, symptom patterns, and functioning helps distinguish PTSD from disorders that may have overlapping signs.

How is PTSD diagnosed in children and adolescents?

While similar principles apply for diagnosing PTSD in younger populations, children and teens can exhibit some different symptoms than adults. The clinical interview must take into account their developmental stage. Some key considerations include:

  • Obtaining collateral history from caregivers, teachers, or others involved in the child’s life
  • Allowing the child or adolescent to complete symptoms scales or questionnaires themselves
  • Be attuned to trauma reactions that manifest as acting out behaviors
  • Looking for trauma triggers at home, school, or with peers
  • Considering language and communication difficulties
  • Remaining alert to the impact of trauma on the child’s social, emotional, and mental development

Paired with clinical judgment, using child-report measures, caregiver reports, and trauma exposure screening tools facilitates an accurate PTSD diagnosis.


Diagnosing PTSD requires specialized clinical skills to conduct a sensitive, thorough interview assessing all symptoms against diagnostic criteria. Screening tools identify people requiring further evaluation, while structured assessments aid in clarifying the presence and severity of symptoms. Information from collateral sources and testing may also facilitate diagnosis. Differential diagnosis is important to distinguish PTSD from comorbid disorders. While following the same principles, assessing children and adolescents must account for developmental factors. An accurate diagnosis guides effective treatment to help those suffering manage disruptive trauma symptoms and improve quality of life.