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Biting Your Nails is… Now a Mental Illness?

By Cathy Thompson

SITTING on the exercise bike this morning at the gym, I read the headline in the Toronto Star: “Nail-biting an obsessive compulsive disorder in new psychiatric classification.” I was taken aback. My son bites his nails—not all of the time, but in moments of stress or anxiety he takes his little 8-year-old hand and chews down the little numbs called nails. As I read the article I hoped that the author would mention the fact that a mental illness becomes an issue when it starts to interfere with daily living – in fact it does say that (phew). But should all of the children who bite their nails starting at age 3 or 4 years old be classified with obsessive compulsive disorder? What if they continue to bite their nails into adulthood – then what? Thinking like a Knowledge Exchange lead for EENet, I decided to investigate this more. What is the evidence?

In the 2009 study cited in the Toronto Star, the researchers write,

Onychophagia can be explained as a kind of a compulsion that may cause destruction of the nails. Habitual nail biting is a common behaviour among children and young adults. By the age of 18 years the frequency of this behaviour decreases, but it may persist in some adults. Nail biting is an under-recognized problem, which may occur on a continuum ranging from mild to severe. Nail biting has received little attention in the psychiatric and dermatological literature. Its position in widely accepted classifications of psychiatric disorders (ICD-10 and DSM-IV) remains unclear. This disorder seems to be related to obsessive-compulsive spectrum disorder.

One additional study I found looks at onychophagia in children and its interrelation to other psychiatric disorders: “Association of nail biting and psychiatric disorders in children and their parents in a psychiatrically referred sample of children, 2008.” A team of researchers, led by Ahmad Ghanizadeh, looked at a sample of 450 children and found some interesting co-morbid psychiatric disorders. 74.6% of the children were identified as having attention deficit hyperactivity disorder (ADHD) and only 11.1% with obsessive compulsive disorder (OCD). The children were being treated at the psychiatric clinic for a variety of issues (not the nail biting); the rates of co-morbid disorders are higher in this population.

In a community sample done in Iran – “Prevalence of nail biting and its association with mental health in a community sample of children, 2011” – 743 children were studied by random sampling. The researchers also echoed that there is co-morbidity of additional psychiatric disorders; however their focus was on general emotional and behavioural problems in children. “The most striking findings of our study,” the researchers noted, “are that emotional and behavioral problems are more common in children with nail biting than those without nail biting.”

One interesting finding shared by a couple of studies was that many of the parents of children who engaged in nail biting had a diagnosis of at least 1 psychiatric disorder.

As the parent of a nail-biter, this is fascinating and something I’d never considered. Nail-biting is more than an annoying habit. But it’s important that the behavior be considered on a continuum. One of the clinical implications of the studies is that clinicians should really look more closely at children who bite their nails to monitor early emotional or behavioural issues. Could this even be considered early intervention? I will be interested to see if this is included in the revised DSM I-V—perhaps next time I’m reading on my exercise bike.

CATHY THOMPSON is a Knowledge Exchange Lead working in the west region of Ontario (Hamilton office). Cathy has a background in Adult and Continuing Education, Addiction, and Mental Health. Her work at CAMH has previously been focused on young women and depression, suicide prevention, tobacco policy, and youth mental health. Cathy has two kids, ages 6 and 8, and loves to spend time with them swimming, biking, and skiing. In her spare time she has founded two organizations: one focused on helping children with their academics (Beyond the Classroom) and the other focused on women’s holistic health (Simply Blossoming).


1. Toronto Star, Nail-biting an obsessive compulsive disorder in new psychiatric classification.–nail-biting-an-obsessive-compulsive-disorder-in-new-psychiatric-classification

2. Pacan P, Grzesiak M, Reich A, Szepietowski JC. Onychophagia as a spectrum of obsessive-compulsive disorder; Department of Psychiatry, Wroclaw Medical University, Poland. Child Adolesc Psychiatry Ment Health; 2009.

3. Ghanizadeh, Ahmad. Association of nail biting and psychiatric disorders in children and their parents in a psychiatrically referred sample of children. Child and Adolesc Psychiatry Ment Health; 2008.

4. Ghanizadeh A, Shekoohi H. Prevalence of nail biting and its association with mental health in a community sample of children. Research Center for Psychiatry and Behavioral Sciences. BMC Research Notes; 2011.