The Science of Sustainability

Is Nail Biting a Pathology? Or Just a Bad Habit?

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Mice bred with a Slitrk5 mutation groom themselves compulsively. Video still courtesy of Nature and Francis Lee

The field of psychiatry is going through major changes this year. For the first time in almost two decades, the Diagnostic and Statistical Manual of Mental Disorders, or DSM, as people in the field call it, is getting an overhaul.

Among the proposed changes: a new category called Obsessive Compulsive and Related Disorders. It would include not just OCD, but other, more common, disorders, including one I know all too well.

I’m a nail biter. And I can tell you the exact moment I became one. I was six years old, watching my mom get dressed for work. As she paused to mull something over, she chewed on the nail of her index finger. How cool! How grown-up, I thought. I think I’ll try it.

I never stopped. In fact, for 30 years, I bit them to the nubs. It was embarrassing. For me, it’s like wearing your neuroses on your sleeve. At parties, I learned to wrap my fingers all the way around my wine glass, so that my nails faced my chest. I hated filling out forms in public places.

Then, recently, something happened that made me finally quit biting my nails. I’ll get to that in a bit.

But I was feeling pretty pleased with myself when I spread my hands out in front of Carol Matthews. She’s a psychiatrist at the University of California San Francisco.

"Pathological Grooming"

“Well, I can see you’re a nail biter,” she told me. Your cuticles are pushed back and you have the bumpiness you see with chronic nail biters. But it’s not bad. It looks like you’re a recovered nail biter, is what I’d say.”

Matthews specializes in pathological grooming, a group of behaviors that includes nail biting, although nail biters rarely come in for treatment. She says the patients she sees the most are the trichotillomaniacs, people who pull their hair out.

Trichotillomania is the most socially visible,” says Matthews. “It's much harder to hide the fact that you don't have eyebrows or that you have a big bald spot, so it’s much more distressing to people. Skin picking comes next.”

In a sense, these behaviors stem from a normal, evolutionarily adaptive behavior: grooming. But in pathological groomers, those behaviors go haywire. Instead of being triggered by, say, a hangnail, a pathological nail-biter will be triggered by all sorts of things: driving, reading a book, or feeling anxious.

From "Not-Otherwise Classified" to "Obsessive-Compulsive Spectrum"

Until recently these pathological grooming behaviors were classified almost as an afterthought in the DSM: “Impulse-Control Disorders Not Otherwise Classified.”

But the new DSM, the DSM-5, proposes something different.

It creates a category called Obsessive Compulsive and Related Disorders that includes classic OCD behaviors, people who wash their hands compulsively or have to line up their shoes a certain way. The idea is to expand this group so that it includes not just OCD, but pathological grooming, as well as hoarding and several other disorders.

This does not mean that insurance companies are going to raise premiums on nail biters, or issue policy-mandated manicures. (In fact nail biting, itself, isn’t even specifically mentioned in the DSM-5, because in the vast majority of cases, it’s not disabling enough to count as a “disorder.”)

But the new classification does give nail biters – and psychiatrists – another way to think about something that used to be considered simply a bad habit. And that raises some questions.

For one, says Mathews, “There’s always the worry of are we over-pathologizing normal behaviors. That’s always a worry with the DSM.”

And does this grouping make sense?


Nail biting? It's a little bit fun.

After all, there are real differences between OCD and those of us who pick, pull, or bite, including one big one.

“In OCD,” says Matthews, “the compulsion is really unwanted.”

People with OCD don’t want to be washing their hands, or checking the stove over and over again, she says. They’re terrified that if they don’t do it, something bad will happen.

But the biters hair pullers and skin pickers? They tell a different story. Matthews says she hears this from her pathological groomers all the time: They enjoy it.

“It's rewarding. It feels good,” she says. “When you get the right nail, it feels good. It’s kind of a funny sense of reward, but it’s a reward.”

Another consideration for the drafters of the DSM-5, when cataloguing all these disorders, is genetics. Are there genetic signatures that help explain both OCD and pathological grooming? Do the two behaviors share any genetic markers? And to what extent are these behaviors hereditary?

Meet the OCD mouse

Francis Lee is a neuroscientist at Weill Cornell Medical College in New York. He studies mice.

A few years ago, a colleague – another mouse guy — came to Lee with a mystery: a mouse, bred with a specific gene mutation, that was behaving very oddly.

“I was dumbstruck,” he says.

The mouse was doing something Lee instantly recognized from his work as a psychiatrist, studying people.

“It was hunched over,” Lee says, “repetitively moving its front paws over its eyes and ears.”

In mice, as in many animals, such grooming behaviors are normal and healthy. But these mice were doing it at a completely different scale. Whereas normal mice might groom themselves for a couple of seconds, mice with this genetic mutation – the Slitrk5 deficiency – groom in bursts of 30 seconds or longer, then start all over again just seconds later.

In fact, the mice groom so much, they give themselves bald spots.

“They remove the hair from around their eyes. They actually look like they have little white rings around their eyes,” says Lee

To Lee, who published this work in Nature Medicine in 2010, this mouse-brand of pathological grooming looks like OCD: a repetitive behavior that the mice are compelled to do. And just like people with OCD, these mice, he says, often exhibit high levels of anxiety and fearfulness. In fact, they’re some of the most fearful, risk-averse mice he’s ever seen.

Lee’s work shows that in mice, a single gene tweak can cause OCD-like symptoms, including over-grooming. Now, scientists are trying to find out whether the same mutations might contribute to OCD, or pathological-grooming, in people.

The (bitten) apple never falls far from the tree

Which brings me to the reason that I finally quit. My daughter Cora, age 3, recently started biting her own nails.

When I asked her about it, she explained, “I don’t want to put my fingers in my mouth. I just do it even though I don’t want to.”

I felt terrible about this. Either I’d waited too long to stop biting my nails and Cora had learned from watching me — the same way I had, with my own mother — or I'd passed on some pathological grooming gene that had her doomed from the start.

Worse, I was making her feel bad about it.

“I’m gonna stop doing it,” she told me. “Why?” I asked. “Because you don’t like me to, remember?" she replied.

In many ways, these questions the DSM is grappling with are the same ones we parents have about our kids. Are our genes their destiny? What’s a bad habit, and what’s a pathology?

The newly revised DSM-5 will be released in San Francisco in May 2013. Maybe around the time Cora’s own kids start biting their nails, she’ll have better answers than we do now.

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Category: Biology, Health, News, Radio

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About the Author ()

Amy Standen is a radio reporter for KQED Science. Her email is astanden@kqed.org and you can follow her on Twitter at @amystanden.
  • Jessica Hill

    I was diagnosed with trichotillomania while I was in middleschool. It was horrifying. It started with my eyelashes. everytime I started thinking about something that worried me I started plucking unconciously. Huge bald patches covered my head and my hair was ratty and stringy. there was no way to hide my obsessive compulsion to pull my hair out strand by strand for every anxious thought. I would sit for hours staring at the wall and plucking. I hated it but I couldn't stop my hands from reaching up and selecting a hair and plucking it out. I had been on Ritalin for two years for hyperactivity. when the hairpulling started my doctor put me on two other kinds of medication for OCD and depression. I hated the all the medication, taking it was one of the things that worried me. years later, after many changes in medication… while I was in highschool I started refusing to take any of it. I started realizing that I could control my reactions to stress without medication and eventually stopped the obsessive destruction. My hair grew back quickly, but the mental scarring never goes away.
    people were really horrible to me because of my physical appearance, and the adults I talked to about my problems only recommended more medication and didn't care that I thought the drugs were hurting me. Let my story be a lesson to all of you. If a child is having problems, the best thing you can do for them is to spend time with them, give them a good example to follow, and listen. Medication that changes a growing bodys brain chemistry should be a last resort.

  • Jessica Hill
  • Rebecca S.

    For anybody here in the Bay Area who wants to learn more about OCD and spectrum disorders, please come to the free presentation and panel discussion featuring Dr. Mathews, October 20, 2-5pm UCSF Langley Porter Institute Auditorium in San Francisco, at 401 Parnassus
    Ave,
    First Floor, Room LP 190. "The Many Faces of OCD" event is being sponsored by the International OCD Foundation – http://www.ocfoundation.org/affiliates/bay-area.

  • Morgan M.

    I'm thankful that this article does not exactly mirror the radio report I heard this morning. In the radio version, Francis Lee described his lab mice by saying "that's a crazy mouse," and moments later Amy Standen, referring to her daughter's nail-biting stated, "I had created a crazy mouse." I was shocked and disappointed to hear the word "crazy" used not once, but twice, to describe a mental disorder. This is exactly the kind of stigmatic word choice that many are working so hard to delete from our lexicon so that mental disorders like OCD can be talked about freely instead of hidden behind closed doors. The more people with mental disorders are described as crazy, the less others with similar disorders are likely to share their stores and seek the help they need. I hope that Ms. Standen and KQED will read this comment and deliver a more thoughtful broadcast in the future.

  • http://www.facebook.com/lizaloop Liza Loop

    I heard this radio piece on KQED this morning (Mon, Sept. 17, 2012). I'm 67 and have been nail-biting, skin-picking and anxious most of my life. I also never got over menopausal hot flashes. One of my sons also bites and picks although not as severely as I do. The other son does not. It is such a relief to consider that this condition may be genetic and not a moral weakness. I would like to participate in genetic studies if anyone is doing them. Perhaps I could enlist my sons as well.

    Some drugs do help. Prozac was effective for me for years and then the condition came back. Recently I've been taking Cymbalta but this is a really nasty, addictive drug. I've been slowly reducing the dosage over the last 5 months in the hopes that I'll be able to avoid the disabling headaches that plague me if I miss even a single dose. Unfortunately, the hot flashes and the anxiety are returning. The picking never went away.

    It's not fun to be a 'crazy mouse' but it's comforting to have company. The good news is that along with the OCD-like symptoms some of us are also very ingenious and creative.

  • Gumora

    This is interesting to me, is the article suggesting the DSM V is "merging" OCD and spectrum disorders categorally, although I am familiar with the my students often diagnosed with both, are they now merging into one? I ask because I have heard the spectrum is expendand to include ADD and other attention/social deficits and droadening overall.

    • gumora

      Opps…so many spelling errors, my apologies, must proof read :)!

  • Sakiara Nguyen