Nail biting isn’t a symptom of ADHD, but it is a behavior that’s commonly linked to people with ADHD. Experts theorize that nail biting is related to ADHD self-stimulating behavior, also called stimming.

Stimming is when a person repeats certain sounds and movements unconsciously, such as lip or nail biting, rocking back and forth, or humming. It’s a coping mechanism for challenges faced by people with ADHD.

For example, a person with ADHD might use stimming to:

  • combat boredom and help maintain focus when completing uninteresting tasks
  • soothe nervousness, anxiety, or stress
  • release excess energy
  • manage sensory overload from such stimuli as bright lights, loud noises, and crowds

While some stimming behaviors can be a helpful coping behavior for people with ADHD, nail biting can lead to unhealthy complications.

Nail biting (also called onychophagia) is a common behavior across the entire population, not just people with ADHD. The habit can be difficult to break once started and can negatively affect your health.

Complications include:

  • Dental problems: Biting your nails repetitively can weaken your teeth and may cause them to change position, chip, or break.
  • Fungal infections: Biting nails can damage the skin around the nailbed and create openings for bacterial and fungal infections. It can also cause your nails to stop growing the way they should, and may lead to hangnails or ingrown fingernails.
  • Illnesses. Nail biting can allow dirt and bacteria to enter your mouth, increasing your risk of illness, such as a stomach bug or the flu.
  • Jaw pain. Frequent nail biting can lead to jaw pain and soft tissue injuries of the mouth.

Rather than trying to stop nail biting altogether, it may be easier to replace it with healthier stimming behaviors. These include:

  • using tools, such as fidget toys
  • practicing doodling or drawing to make listening easier
  • wearing textured clothing for finger stimming
  • wearing noise-reducing headphones to block loud or distracting sounds
  • practicing self-calming techniques such as deep breathing and meditation

Have a conversation with a medical professional if you’re trying to replace nail biting with other coping mechanisms. Participating in behavior therapy can help redirect certain unwanted stimming behaviors, such as nail biting.