Post-traumatic stress disorder (PTSD) is officially diagnosed by a qualified mental health professional (psychiatrist, clinical psychologist, or licensed therapist) using criteria from one of two main classification systems:

1. DSM-5-TR (Diagnostic and Statistical Manual of Mental Disorders, 5th edition, Text Revision) – used primarily in the United States.
2. ICD-11 (International Classification of Diseases, 11th revision) – used internationally and by the World Health Organization.

Both require that symptoms last more than one month and cause significant distress or impairment in social, occupational, or other important areas of functioning.

DSM-5-TR Criteria (most commonly referenced):

• A. Exposure to actual or threatened death, serious injury, or sexual violence (directly experiencing, witnessing, learning it happened to a close family member/friend, or repeated/extreme exposure to aversive details, e.g., first responders).
• B. Intrusion symptoms (≥1): flashbacks, nightmares, intrusive memories, intense distress/physical reactions to triggers.
• C. Persistent avoidance (≥1): avoiding trauma-related thoughts/feelings or external reminders (people, places, conversations, etc.).
• D. Negative changes in cognition/mood (≥2): inability to recall key aspects, exaggerated negative beliefs, distorted blame, detachment, inability to experience positive emotions, etc.
• E. Marked changes in arousal/reactivity (≥2): irritable/angry outbursts, hypervigilance, exaggerated startle, concentration problems, sleep disturbance.
• Symptoms must begin or worsen after the trauma and not be better explained by substance use or another medical/psychiatric condition.

ICD-11 is slightly narrower, requiring only three core symptom clusters (re-experiencing, avoidance, and heightened sense of threat) plus functional impairment.

Diagnosis is made through a structured clinical interview (e.g., the Clinician-Administered PTSD Scale – CAPS-5, considered the gold standard), review of history, and ruling out other conditions. Self-report questionnaires (PCL-5, etc.) help screen but are not diagnostic on their own.

There is no blood test or brain scan that can definitively diagnose PTSD. Diagnosis relies on clinical judgment by a trained professional. If you suspect PTSD, seek evaluation from a licensed mental health provider experienced in trauma. Early diagnosis improves treatment outcomes significantly.