Many people have bad habits. These may include arriving places late, unhealthy eating or cramming for a school exam or work project at the last minute. Though frustrating, such habits are often manageable and voluntary. 

But other people struggle with bad habits of a different variety, ones caused by anxiety or brain or environmental abnormalities. Such limiting behaviors can range from obsessive-compulsive disorder (OCD) to tics and twitches. Individuals struggling with anxious tics, "may find them hard to control and find it very difficult to stop," says Jesse Bracamonte, MD, DO, a family medicine physician at Mayo Clinic in Arizona.

One habit that can fall into either category is nail biting. 

How common is nail biting? 

Nail biting, or onychophagia as it's called medically, is very common. Up to 30% of the population does it, according to UCLA Health. And it's even more common in children − with as many as 50% of kids participating in the practice, per another report. 

Despite such common prevalence, nail biting can sometimes be a sign of an underlying issue that needs to be addressed and may have negative health outcomes. "Nail biting can lead to cosmetic problems with the nails or infection due to the mouth bacteria being transferred to the fingers," cautions Bracamonte. Nail biting can also cause ingrown nails, temporomandibular joint pain and dysfunction, and may harm one's teeth through chipping or misalignment issues. 

Why do people bite their nails?

The first step in getting to the bottom of the behavior is recognizing that the habit has a spectrum that ranges from the benign to the worrisome. In the former category, nail biting isn't necessarily something to be overly concerned about, especially in children. "Parents often assume that kids bite their nails because of anxiety or stress, but kids also bite their nails for many other reasons such as curiosity, boredom, habit, self-soothing or cosmetic reasons," explains Cathryn Tobin, MD, a pediatrician, parenting expert, and author of "The Parent's Problem Solver." 

For adults and some children, anxiety and stress may contribute more broadly and sometimes there's even a mental health condition at play. And often adults are similar to kids in that they sometimes "bite their nails due to boredom or from the behavior becoming a habit due to having a physical finding such as a hangnail," says Bracamonte. He adds that the habit may have also developed by watching another person do it.

The fact that the habit can be brought on by both understimulation (boredom) and overstimulation (stress or anxiety) is one of the reasons it's so common. 

How to stop biting your nails

When dealing with boredom and benign elements of the habit, it's helpful to know that many kids grow out of the behavior naturally and that most adults can stop biting their nails easily. But there are some tips and techniques that may be helpful. "Keeping nails trimmed with the use of a nail trimmer, identifying the triggers that cause nail biting and finding alternative ways to deal with triggers such as using a stress ball may help with breaking this habit," offers Bracamonte. Getting to the bottom of one's stress or anxiety through professional help or lifestyle changes may also be necessary. 

Tobin says that when helping children break the habit, it's wise to start by remembering that some habits are hard to break, so patience is key. She explains that over nearly three decades of working with children, she's learned about some of the tricks that don't work. These include employing pressure, nagging or shaming. 

Instead, she recommends trying to help the child see that you're not the opponent, but their teammate. "Ask your child, 'What can I do to help you stop biting your nails?'" she suggests. She says the motivation should be about creating an environment "where they feel backed up, understood and seen" by acknowledging that it can be hard to stop and by recognizing their efforts and progress. She's also recommends keeping the child's hands busy with other things like a rubber ball or silly putty, reminding the child often, and taking things slowly and pressure free.