Post-traumatic stress disorder (PTSD) does not affect everyone exposed to trauma equally. Certain groups and factors dramatically increase the likelihood of developing PTSD.

The highest-risk individuals are those who experience severe, interpersonal, or prolonged trauma, especially involving threat to life, serious injury, or sexual violence. According to the National Center for PTSD (U.S. Department of Veterans Affairs) and large-scale studies (e.g., Kessler et al., 2017; Atwoli et al., 2015), the following groups consistently show the highest PTSD rates:

• Sexual assault survivors: Lifetime PTSD rates reach 30–50% (women) and 20–30% (men) after rape the single highest-risk event.
• Combat veterans, especially those with prolonged or intense exposure: 15–30% of Vietnam veterans, 11–20% of Iraq/Afghanistan veterans.
• Refugees and victims of torture: Rates often exceed 30–50%.
• First responders (police, firefighters, paramedics) with repeated trauma exposure: 10–20% lifetime prevalence, higher in high-violence areas.
• Childhood sexual or physical abuse survivors: 35–50% develop PTSD, especially when abuse is repeated or perpetrated by a caregiver.
• Victims of domestic violence and human trafficking.

Additional risk factors that amplify danger include:

• Female gender (women are roughly twice as likely as men to develop PTSD after similar trauma)
• Prior trauma history (especially in childhood)
• Lack of social support after the event
• Pre-existing mental health conditions
• Peritraumatic dissociation or intense fear/horror during the event

In contrast, one-time accidents, natural disasters, or sudden loss of a loved one carry lower conditional risk (typically 5–15%).

In short, the highest-risk individuals are survivors of intentional, interpersonal violence particularly sexual assault, childhood abuse, torture, and prolonged combat with risk compounded by prior trauma, female sex, and poor post-trauma support.