Nail-biting may not only increase a person's risk of falling prey to illness from bacteria, but new research indicates that those who worry incessantly may also be more at risk for developing post-traumatic stress disorder (PTSD), a mental health condition related to anxiety disorder. People with PTSD have either been a victim of or witness to an event which inflicted serious harm or threat of harm. The disorder can result from military combat experiences, but affects many more through violent crime, natural disaster or traumatic events such as vehicular crashes. Not everyone who lives through these types of serious events develops PTSD. Many, in fact the vast majority of people, experience an initial period of shock and distress, but go on to cope effectively and healthfully with the fears and memories brought on by the event(s). The search for what determines who develops PTSD and who does not was behind a Michigan study. The study involved 1,000 subjects who were chosen randomly, interviewed, and then followed for a decade. Initially, each studies participant was given a dozen questions designed to measure their neuroticism. Neuroticism is a term for strong anxiety. Neurotic persons, or persons with excessive anxiety, exhibit disproportionate reactions to daily struggles. The questionnaire effectively established an anxiety baseline for each participant. During the ten year study period participants were re-assessed at the three, five and ten year mark. Over the course of the study, 50 percent of the subjects lived through some sort of traumatic experience. Researchers discovered that those with the highest neuroticism (anxiety) scores were the most likely to fall within the five percent of those who ended up developing PTSD following trauma. This means that people with high levels of anxiety, or those who could be termed chronic worriers, are the most vulnerable to developing PTSD in the face of an overwhelming trauma. The greater a person's pre-existing neurosis, the greater chance they run of struggling with PTSD when\/if an extreme event occurs in their life. A propensity for worry will not disappear in the face of tragedy, it will become more problematic. The scientists involved in the Michigan study admit that they had an advantage in holding a before-the-event baseline. Most PTSD studies have necessarily focused on gauging anxiety after-the-fact. Since it is impossible to prevent PTSD, the researchers suggest that their research underscores the necessity of getting to know patients well in the aftermath of disaster. Health care providers are advised to look for signs of prior psychiatric illness and anxiety\/chronic worry in particular when treating patients who have undergone a traumatizing experience. Furthermore, since it is likely that most individuals will be faced with a potentially traumatizing event at some point in life, doctors who emphasize the importance of healthy coping during periods of relative peace are offering their patients crucial health support. There is no up-side to chronic worry.