The main cause of deep vertical nail ridges is normal aging, states About.com. They can also be caused by trauma, and in rare cases, by a systemic medical condition, according to Healthgrades.
Typical results of aging are loss of moisture and skin dehydration, which can deplete oils that naturally occur in skin, hair and nails, notes About.com. The loss of these oils can result in nail ridges. Keeping cuticles and nails moistened can help minimize their appearance. The root cause of age-related development of ridges is not exactly known, reports Mayo Clinic. It may be related to inconsistent cellular development associated with aging.
Although aging is the most common cause, deep nail ridges that appear suddenly may be caused by trauma, as noted by Healthgrades. Trauma to nails can result from slamming a nail into a car door or hitting it with a hard or heavy object, such as a hammer.
Horizontal ridges, called Beau's lines, develop when there is an interruption in the nail growth due to trauma or disease, explains Mayo Clinic. Diabetes and peripheral vascular disease can cause them as well as diseases associated with high fevers, such as scarlet fever, pneumonia, mumps and measles. A deficiency of zinc can also cause Beau's lines.