PTSD is characterised by recurrent and intrusive recollections of the stressful event, either in flashbacks (images, thoughts, or perceptions) and/or in dreams. There is an associated sense of re-experiencing of the stressful event. There is marked avoidance of the events or situations that arouse recollections of the stressful event, along with marked symptoms of anxiety and increased arousal. The other impoant clinical features of PTSD include paial amnesia for some aspects of the stressful event, feeling of numbness, and anhedonia (inability to experience pleasure). Ref: A Sho Textbook of Psychiatry, Niraj Ahuja, 7th Edition, pg. no. 112