The last two days of life of nursing home patients--a nationwide study on causes of death and burdensome symptoms in The Netherlands. Palliat Med 2006; 20:533. Wright AA, Keating NL, Balboni TA, et al. Place of death: correlations with quality of life of patients with cancer and predictors of bereaved caregivers' mental health.
1. Respiratory Health Issues. Downward curved fingernails can indicate a problem with respiratory health, and are often present in people who have medical conditions such as COPD, chronic bronchitis, asthma and lung cancer. Fingernails often curve downwards as a result of lack of oxygen.
When it comes to picking out the causes for a nail biting habit, psychologists have pinpointed virtually everything under the sun. Some stick to a fairly conventional explanation: that it's due to preoccupation, boredom, tiredness, or a wish for simple comfort. Others, however, have more out-there explanations.