Stress is the body's normal response to anything that disturbs its natural physical, emotional, or mental balance. Stress reduction refers to various strategies that counteract this response and produce a sense of relaxation and tranquility. Although stress is a natural phenomenon of living, stress that is not controlled and that continues for a long period of time can seriously compromise health. For this reason, stress must be understood, managed and appropriately reduced. Several very different strategies and therapies are available that help with relaxation and stress management. Stress reduction can only present a problem if an individual attributes an actual, serious condition or disease to being simply a stress-related response and avoids consulting a physician. People who have undergone a severe trauma (criminal assault, combat, natural or transportation disaster, etc.) may experience symptoms of posttraumatic stress disorder (PTSD) or acute stress disorder (ASD). These disorders are defined by their temporal connection to a traumatic event in the patient's life, and are characterized by a cluster of anxiety and dissociative symptoms. They interfere with the patient's normal level of functioning, and require some form of supportive therapy. People who experience a sense of detachment or unreality, emotional numbing, a general feeling of being dazed, amnesia for part of the traumatic event, or similar symptoms should consult a medical doctor in addition to using other approaches to stress reduction.