PTSD affects 3.6% of the U.S. adult population—about 9 million individuals. About 37% of those diagnosed with PTSD are classified as having severe symptoms. Women are significantly more likely to experience PTSD than men.
Young children can also develop PTSD, and the symptoms are different from those of adults. (This recent recognition by the field is a major step forward and research is ongoing.) Young children lack the ability to convey some aspects of their experience. Behavior (e.g. clinging to parents) is often a better clue than words, and developmental achievements in an impacted child might slip back (e.g. reversion to not being toilet trained in a 4-year-old).
It is essential that a child be assessed by a professional who is skilled in the developmental responses to stressful events. A pediatrician or child mental health clinician can be a good start.
Provided by National Alliance on Mental Illness (NAMI) at https://nami.org/About-Mental-Illness/Mental-Health-Conditions/Posttraumatic-Stress-Disorder