Which of the following is a symptom typical of Posttraumatic Stress Disorder (PTSD)?

Frequent nightmares related to trauma is a hallmark symptom of Posttraumatic Stress Disorder (PTSD). Individuals with PTSD often experience intrusive memories of the traumatic event, which can manifest as nightmares that vividly replay the trauma or incorporate elements of it. This symptom is part of the re-experiencing cluster of PTSD symptoms, where individuals are unable to escape reminders of their trauma, causing significant distress and impairment in daily functioning.

The other options do not accurately represent symptoms of PTSD. While an inability to enjoy everyday activities may relate to depression or another disorder, it is not specific to PTSD. Constant feelings of happiness would contradict the distress typically experienced in PTSD and is not a symptom of the disorder. Thus, the presence of frequent nightmares aligns closely with the diagnostic criteria for PTSD and emphasizes the impact of trauma on an individual's mental health.