Which of the following is a key symptom of anxiety related to posttraumatic stress disorder?

Intrusive memories are indeed a key symptom of anxiety related to posttraumatic stress disorder (PTSD). Individuals with PTSD often experience distressing thoughts or flashbacks about the traumatic event they have experienced. These memories can occur unexpectedly and can be triggered by various stimuli, leading to significant distress and anxiety. The presence of these intrusive memories is not only a hallmark feature of PTSD but also directly contributes to the heightened anxiety that individuals may feel as they struggle to cope with their past experiences.

The other options do not align with the common symptoms associated with anxiety in PTSD. A heightened sense of security is contrary to the typical experiences of those with PTSD, who often feel unsafe or hyper-vigilant. Improved concentration is generally not a symptom seen in individuals experiencing anxiety; rather, anxiety can impair focus and attention. Effective coping mechanisms would suggest a level of resilience and management of symptoms, which is often not the case for those suffering from PTSD-related anxiety, where coping can be severely challenged.