<qa>  What is the inactive sugar pill?Victims of serious motor vehicle collisions will be evaluated with clinical assessments and standardized questionnaires within 2 weeks after the accident. Symptoms of exaggerated startle, emotional reactivity to trauma-related and trauma-unrelated cues, and cerebellum functioning will be evaluated. Participants will be randomized to receive either sertraline or placebo an inactive sugar pill for 8 weeks. Psychometric testing and psychological evaluations will be conducted 4, 10, and 14 weeks after the accident and after a 2-week taper of the study medication. 