In my work with patients recovering from auto accident trauma, a frequent problem patients report is sleep disturbance due to racing thoughts that play over and over in their minds.

In psychiatry this is referred to as ruminating thoughts which can be symptomatic of depression and anxiety states.  This is particularly common in post-traumatic stress disorder where intrusive thoughts related to a traumatic event tend to haunt the mind while attempting to enter the sleep state.  Frequently, this involves the perfect storm of the fear of entering the dream state due to likelihood of having trauma related nightmares, worries related to the trauma, and often bodily sensations and sometimes physical pain, resulting from or symbolic of the trauma.

Read more at Psychology Today.