Many people will experience different symptoms of post-traumatic stress disorder (PTSD) in type and severity. Still, a few of the main symptoms to look out for include intrusive memories, avoidance, negative changes in thinking and mood, and changes in physical and emotional reactions. Intrusive memories cover all unwanted memories of the traumatic event that are recurrent, or feel as if the person is reliving the event through flashbacks, can include upsetting dreams or nightmares related to the traumatic event, and the experience of negative emotional or physical reactions to anything reminiscent of the traumatic event. The symptom of avoidance is when the person who has experienced a traumatic event avoids talking or thinking about the event, as well as avoids places, people, activities, or anything else that may remind them of the traumatic event. Negative changes in thinking or mood may be displayed as having negative thoughts about yourself, or those around you, feeling hopeless about the future, having problems with memory, struggling to maintain close relationships, experiencing detachment from friends or family, losing interest in previously enjoyed activities, struggling to experience or display positive emotions, and experiencing feeling numb. The symptoms displayed with changes in physical and emotional reactions may include the ability to be frightened or startled easily, feeling a constant need to be on guard for danger, displaying destructive behavior (substance abuse or excessive speeding), insomnia, struggling to concentrate, behavior that is aggressive, outbursts of anger, or irritability, and experiencing overwhelming feelings of guilt or shame.