This might sound impossibly lame, but I have never cut my fingernails and if someone gave me a nail clipper, I would probably leave myself with ten raw stumps for fingers. I have been biting my nails for literally as long as I can remember, so it’s no exaggeration to say that stopping is tackling the habit of a lifetime.
I know that being a nail biter is unusual, but I never really thought about why I did it, what it meant, or how to stop. Now that I think about it, that’s strange, because I’m a psychologist and this kind of this is exactly what I am interested in – in other people.
My mum, and then my wife, have collectively been nagging me about it for what must be the best part of 25 years, but as with tackling nearly all bad habits/addictions, the decision to stop works best if it comes from within. They both deserve credit for trying to be helpful and persisting in trying to get to me to break the habit, but to be honest, it had just became background noise.
I don’t know what’s suddenly made me stop, but I made the decision last Wednesday and 12 days later I still haven’t bitten them. My nails are now long enough that I will have to actually cut them in a couple of days. How long this will last, I don’t know. I did stop biting them once before, about five years ago, but I wasn’t successful and I’m not sure if that even counts as an attempt to tackle the problem. I can’t remember why I decided to stop biting them that time or what made me start up again.
Reflecting on the whys and wherefores of nail-biting now that I am attempting to break the habit has been really helpful and has motivated me to look up the science and psychology behind it and write up what I have learned.
It’s estimated that around a third of children between 7 and 10 years of age bite their nails and this goes up to 45% in teenagers . After this peak in adolescence the prevalence starts to taper down to around 25% of young adults and then only 5% of adults – the ‘select’ group to which I (used to!) belong. Whilst it is unusual, it is not unheard of for people to continue biting theirnails well into old age.
The scientific name for nail biting is onychophagia (on-i-koh-fey-juh). A different, but strongly related, condition is onychotillomania, which is another form of self-induced damage of the nails caused by recurrent picking and manicuring of the nails. Compulsively biting just the skin is called dermatophagia. Along with hair pulling (trichotillomania) and skin picking (dermatillomania), nail biting is classed as a body-focused repetitive behaviour disorder (RBD), which results in physical and psychological difficulties.
It was a shock to see what I did labelled a disorder, but I fall on the lower end of RBD severity, where it’s more of a ‘nervous habit’. It becomes a real problem, and more like a disorder as most people understand it, when it starts to have a significant impact on everyday functioning. When these kinds of repetitive behaviours cross this important line, they are classified as impulse control disorders according to the Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV), a comprehensive compendium used by clinicians and psychologists to describe and categorise mental health disorders and psychiatric illness.
Compulsive nail biting is often observed in people suffering from obsessive-compulsive disorder and body dysmorphic disorder. Because nail biting is a repetitive behaviour and common in people with obsessive-compulsive disorder, it is sometimes considered a related obsessive-compulsive spectrum disorder . The most well-understood form of compulsive self-mutilation is hair pulling, and this also tends to disproportionately afflict people with OCD.
I might well be on the milder end of this spectrum, but this description on the NeuroBehavioural Institute webpage is something that I can definitely relate to:
Over the course of my mini adventure in self-diagnosis, I came across several theories and explanations for what causes nail biting behaviour and what functions it might have. Nail biting is commonly linked to anxiety, most obviously with the phrase ‘nail-biting finish’ in sports, but the basic cause of onychophagia is difficult to pin down. If it is a manifestation of anxiety, there is still some discussion about whether it is related to state-anxiety (being in a particular stressful situation)  or trait-anxiety (having a naturally anxious personality) . A study of 743 randomly selected primary school children found that around 20% of them bit their nails and there was a trend for nail biters to have higher scores on scales of emotional problems (for example hyperactivity/inattentiveness and conduct problems ) than those that didn’t .
On the other hand, the cause may be nothing to do with an underlying emotional disturbance. Although I personally associate biting my nails with being stressed, particularly with work and especially when I was writing my PhD thesis, it wasn’t always stress-induced. I sometimes found myself absent-mindedly biting when watching TV or reading, and it was more about getting rid of that tiny nick in my nail or bit of skin that had come loose around my cuticle. In one study of 40 undergrad psychology students, the most common reason for nail biting was boredom .
Saying nail biting is caused by anxiety or emotional problems doesn’t really get at the heart of the cause. There are lots of ways that people can manifest their stress – what I really wanted to get at was why I specifically decided to bite my nails. The most likely explanation is that it is a combination of biological and environmental factors. Nail biting may be a hangover of our evolutionary history: neurobiological models of RBDs and OCD propose that these types of behaviours are grooming mechanisms from our evolutionary past that have gone awry. Many animals engage in excessive skin picking and scratching, and some have theorised that an out-of-control grooming mechanism in the brain causes behaviours like nail biting and particularly hair pulling. Animal models suggest that there might be a genetic cause. Mutations of the Hoxb8 gene in mice have been associated with excessive grooming behaviours , an equivalent of hair pulling in people with OCD.
Brain regions such as the right frontal cortex, anterior cingulate cortices and putamen, which control mechanisms that regulate mood, behaviour and cognitive control and generating and suppressing motor habits, have been implicated in neuroimaging studies of people with hair pulling [8, 9] , but the same studies have yet to be done with nail biters.
Genetic explanations might also help explain why nail biting tends to occur in families. In the large study of school children I mentioned earlier, 55.8% of children who had at least one sibling had a at least one of their siblings or parents bite his/her nails frequently. Rather than nail biting being an acquired behaviour that children learn (for example from their close family), as some people have suggested, it may be a result of shared genetic mutations that leave children predisposed to this kind of behaviour, which might then be triggered by environmental factors such as anxiety, stress or boredom. That said, it’s only ever been me that has bitten my nails in my family, so I belong with the 44.2% of children who do not have a family member who bites.
Different treatments work for people in different ways. Trying to treat nail biting, as with trying to tackle any bad habit, needs to consider age, intensity and frequency of the action, situations triggering the habit and emotional conditions. The following quote from a paper discussing nail biting research goes some way towards explaining what I said earlier about my mum and wife’s failed attempts at helping me stop biting:
“Treatment should be directed at the causes; punishment, ridicule, nagging and threats, and application of bitter-tasting commercial preparations on the nail are a variety of reminders, but are not appropriate approaches to treatment” .
Treatments for nail biting can be broken down into two different categories:
Aversion therapies rely on what’s called operant conditioning to try to stop nail biting by using negative reinforcers that make performing the behaviour unpleasant.
Bitter-tasting nail varnishes are probably the most widely recognised form of treatment for nail biting and there are lots of them on the market. They might work for some people, but for the hardened biter like me, they didn’t – as a child I eventually learned to tolerate, and I think even like, the taste. I guess using them as an adult is even trickier because you require the self-discipline to apply nail varnish in the first place.
Two forms of self-punishment therapies that also fall under this category include snapping an elastic band on the inside of the wrist  and a study from the 60s that I came across that tested the use of a portable shock device as a negative reinforcer .
The results for both were variable, and given how impractical the shock device is, I’m not really surprised that it never really took off.
Cognitive therapies target the thoughts and actions related to nail biting.
Self-monitoring involves becoming aware of the biting behaviour, which is often unconscious, and writing it down or recording it in some way. The act of stopping to record the behaviour can help interrupt the process, which can reduce the nail biting and help to identify (and subsequently change or avoid) the environmental factors or moods that trigger compulsive nail biting. A couple of studies from the 70s [11, 13] have shown that self-monitoring on its own may help some people, but that it’s more effective when followed with additional therapies like positive or negative reinforcers.
Competing response therapies aim to provide an alternative to nail biting, which interrupts the biting behaviour by occupying the hands or mouth. A study of 21 young adults  found that both mild aversion therapy (using a bitter nail varnish) and a competing response action (clenching the fist whenever there was a urge to bite) both resulted in longer nails, with the fist-clenching technique working best. Another study from the 70s also found that fist clenching resulted in lower long-term relapse rates .
As an aside, I also came across a trial on the efficacy of hypnosis , but, unsurprisingly, it was found that believing it will work was more important than the actual hypnosis itself.
The competing response therapy is the one that seems to be working for me at the moment, as I found myself naturally clenching my fists to stop myself before I had even read this paper or looked into anything in detail. All of these therapies are aimed at simply eradicating the behaviour, not the underlying cause, and as such are more appropriate for the milder end of nail biting/OCD spectrum. In cases were nail biting is directly related to an anxiety or OCD, counselling and drug therapies may be more appropriate.
It is curious that a lot of the literature that I came across on nail biting, particularly when trying to look up incidence rates, is pretty old now. I reckon it’s because in most cases it is just dismissed as ‘nervous fidgeting’ that eventually goes away, and it doesn’t have the same impact as hair pulling.
I still don’t know the precise reason why I took to biting my nails, but reading up on the causes and psychology of my nail biting problem has been really interesting and understanding the problem goes a long way to overcoming it. Hopefully I won’t have to write a follow-up detailing the psychology behind my relapse.
1. Leung, A.K. and W.L. Robson, (1990), Nailbiting. Clin Pediatr (Phila). 29, 12, 690-2.
2. Pacan, P., et al., (2009), Onychophagia as a spectrum of obsessive-compulsive disorder. Acta Derm Venereol. 89, 3, 278-80.
3. McClanahan, T.M., (1995), Operant learning (R-S) principles applied to nail-biting. Psychol Rep. 77, 2, 507-14.
4. Joubert, C.E., (1995), Associations of social personality factors with personal habits. Psychol Rep. 76, 3, 1315-21.
5. Ghanizadeh, A. and H. Shekoohi, (2011), Prevalence of nail biting and its association with mental health in a community sample of children. BMC Res Notes. 4, 1, 116.
6. Williams, T.I., R. Rose, and S. Chisholm, (2007), What is the function of nail biting: an analog assessment study. Behav Res Ther. 45, 5, 989-95.
7. Graybiel, A.M. and E. Saka, (2002), A genetic basis for obsessive grooming. Neuron. 33, 1, 1-2.
8. Chamberlain, S.R., et al., (2009), Trichotillomania: neurobiology and treatment. Neurosci Biobehav Rev. 33, 6, 831-42.
9. Aron, A.R., et al., (2007), Triangulating a cognitive control network using diffusion-weighted magnetic resonance imaging (MRI) and functional MRI. J Neurosci. 27, 14, 3743-52.
10. Tanaka, O.M., et al., (2008), Nailbiting, or onychophagia: a special habit. Am J Orthod Dentofacial Orthop. 134, 2, 305-8.
11. Horan, J.J., (1974), Self-control of chronic fingernail biting. J Behav Ther & Exp Psychiat. 5, 307-9.
12. Bucher, B.D., (1968), A pocket-portable shock device with application to nailbiting. Behav Res Ther. 6, 3, 389-92.
13. Adesso, V.J., J.M. Vargas, and J.W. Siddal, (1979), The Role of Awareness in Reducing Nail-biting Behavior. Beh Therapy. 10, 148-54.
14. Silber, K.P. and C.E. Haynes, (1992), Treating nailbiting: a comparative analysis of mild aversion and competing response therapies. Behav Res Ther. 30, 1, 15-22.
15. Horne, D.J. and J. Wilkinson, (1980), Habit reversal treatment for fingernail biting. Behav Res Ther. 18, 4, 287-91.
16. Wagstaff, G.F. and C. Royce, (1994), Hypnosis and the treatment of nail biting: A preliminary trial. Contemporary Hypnosis. 11, 1, 9-13.