People who bite their nails compulsively (of which I am one), might soon see their disgusting but (relatively) harmless bad habit classified as an obsessive/compulsive disorder!
The American Psychiatric Association —which publishes the Diagnostic and Statistical Manual of Mental Disorders (DSM)—has announced that they will now classify nail biting as an obsessive/compulsive disorder (OCD). OCD is most-commonly characterized by unreasonable or irrational thoughts and fears (obsessions) that lead you to do repetitive behaviors (compulsions), such as washing your hands several hundred times a day from fear of bacteria and germs.
For you more casual nail biters (I'll place myself in this category so I don't feel like a total nutjob), relax. Only more severe cases where people have actually eaten away their entire nails to the point of contracting infections will currently be classified as OCD.
You casual nail biters, however should read this word of caution from medical experts: Biting away at your fingernails can contribute to skin infection, aggravate existing conditions of the nail bed, and increase the risk of colds and other infections by encouraging the spread of germs from the nails and fingers to the lips and mouth.
My mother used to dip my nails in castor oil to keep me from biting them as a child, until I developed a taste for the nasty stuff! I'll have to think of something that tastes more disgusting to soak my nails in now...