Also, worry and intrusive thoughts, disturbing images of what happened might interfere with falling asleep.
Similarly, people who are reacting to a traumatic experience might find their sleep interrupted. There are certain startle mechanisms that can actually operate within sleep and so people's sleep might be interrupted by a sudden startle or apprehension that wakes them up.
Finally, particularly intense, life-threatening experiences can affect what one dreams about and the experience of dreams. A person who has experienced a severely threatening event might dream about that event. And the dream might be rather realistic in its content, which contrasts more typical dreams, which are kind of mixed-up and sometimes bizarre.
How do these sleep problems affect the daytime behavior?
The person may feel on guard, irritable and upset. The person may be fatigued because of sleep loss, and at the same time on guard and over-vigilant. This can be an uncomfortable combination and it might make focusing, concentrating and attending to the here and now more difficult.
And finally, distressing dreams can be remembered into the daytime. In a sense, they can become a form of extended trauma, or re-traumatization. Conversely, I think sometimes dreams evolve over time and can actually help facilitate a person's emotional recovery.
