咬指甲，精神失常还是只是坏习惯？

STEVE INSKEEP, HOST: It's MORNING EDITION, from NPR News. I'm Steve Inskeep. Today in "Your Health," nail biting, which is one of the most common childhood habits - which for some, lasts into adulthood. Some nail biters can become pathological groomers, people for whom normal grooming behaviors - like skin picking, or hair pulling - have become almost uncontrollable.

The field of psychiatry is changing the way it thinks about pathological grooming, and those changes will be reflected in a new manual of mental disorders, which is coming out next year. This rethinking gives pathological groomers some new ways to think about their behaviors - including KQED's Amy Standen.

AMY STANDEN, BYLINE: I am a nail biter, and I can tell you the exact moment I became one. I was 6 years old, watching my mother get dressed for work. As she paused to mull something over, she chewed on a nail. How cool; how grown-up, I thought. I think I'll try it. And I never stopped - for 30 years.

I was embarrassed by it. For me, it was 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.

Now, recently, something happened that made me finally quit biting my nails; I'll get to that in a bit. But I was feeling quite pleased with myself when I showed them off to Carol Mathews. She's a psychiatrist at the University of California, San Francisco.

DR. CAROL MATHEWS: Your cuticles are pushed back. It's not bad; it looks like you're a recovered nail biter.

STANDEN: Mathews specializes in pathological grooming. This is a group of behaviors that includes nail biting, but also people who pull their hair out - that's called trichotillomania - or pick at their skin. They are behaviors that stem from normal grooming. The kind of thing...

MATHEWS: That most animals do, and is evolutionarily adaptive.

STANDEN: But in pathological groomers, those behaviors go haywire. Instead of being triggered by, say a hangnail, the pathological nail biter is triggered by driving, reading, feeling stressed out.

MATHEWS: After a while, the behavior becomes un-triggered. It becomes just an automatic behavior that has no relationship to kind of external stimuli, at all.

STANDEN: Until recently, the DSM - that manual of mental disorders - treated pathological grooming kind of like an afterthought. It was in a catch-all category called "not otherwise classified." But the new DSM proposes something different. It proposes to lump together pathological grooming and another disorder you've probably heard of - OCD, or obsessive compulsive disorder. So that includes people who wash their hands compulsively, or have to line up their shoes in a certain way.

Now, there's a lot these behaviors have in common. In both cases, it's taking a behavior that is normal and healthy, and putting it into overdrive - doing it to the point where it is excessive. But there is at least one way that OCD and pathological grooming are also very different. Again, Carol Mathews.

MATHEWS: In OCD, the compulsion is really unwanted.

STANDEN: People with OCD don't want to be washing their hands, or checking the stove over and over again. There is no fun in it. What there is, is fear; fear that if they don't do something, something else - that is very bad - will happen to them. But from her pathological grooming patients, Mathews hears a very different story. They enjoy it.

MATHEWS: Yeah, it's rewarding. It feels good. When you get the right nail, it feels good. It's kind of a funny sense of reward, but it's a sense of reward.

STANDEN: I can relate to that. And in my household, I am not the only one.

CORA: Mommy, I could draw a volcano.

STANDEN: Really? Let's see it.

CORA: OK.

STANDEN: This is my daughter, Cora.

CORA: And here's a little baby bird.

STANDEN: Oh, yeah?

CORA: Yeah.

STANDEN: She's 3. And recently, I noticed something she had started to do.

You know when you put your fingers in your mouth, like that? What does that feel like?

CORA: But I don't want to put me in my mouth. I just - just doing it, even though I want - I don't want to.

STANDEN: You're doing it even though you don't want to?

CORA: Yeah.

STANDEN: This is the reason I had decided to quit. I didn't want Cora to learn to bite from me, the same way I had learned from my mom. So for three months I had worn acrylic fingernails, kept them maintained with regular manicurist visits. And it worked. I lost the urge. But apparently, it was too late.

Do you ever see me put my fingers in my mouth?

CORA: Sometimes.

STANDEN: Really?

CORA: When do you put your fingers in your mouth?

STANDEN: But was she mimicking me, or was there something else going on? Something deep - and strong enough to make nail biters out of at least four generations of women in my family, including my grandmother.

DR. FRANCIS LEE: What we're doing is, we're walking - right now - to my laboratory.

STANDEN: And that is where Francis Lee comes in.

LEE: And if you want to, we can start by first looking at the mice.

STANDEN: Lee is a psychiatrist and neuroscientist, at Weill Cornell Medical College in New York. 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.

LEE: I was dumbstruck.

STANDEN: Because the mouse was doing something Lee instantly recognized, from studying people.

LEE: It was just repetitively moving its front paws over its eyes and ears.

STANDEN: These mice groomed so much, they gave themselves bald spots.

LEE: They've removed all the hair around their eyes, so you - they actually look like mice that have little, white rings around their eyes.

STANDEN: In these mice, genome is destiny. Every mouse that has this particular mutation - even if it's separated from its mother early on - eventually will become a pathological groomer. And the grooming isn't all. Lee says these are some of the most anxious mice he has ever seen. He even said so to his colleague, at the time.

LEE: That is one crazy mouse.

(LAUGHTER)

STANDEN: People, of course, are a lot more complicated than mice. There are some genetic mutations that seem to crop up in people with OCD, and in people who groom pathologically. But just because you have the mutation, doesn't mean you get the behavior. In fact, with OCD, it's more likely that you won't, says Carol Mathews.

MATHEWS: As genetically determined as OCD is, the risk to a family member who - for somebody who has OCD, is only 20 percent. So it's 80 percent chance of not getting it.

STANDEN: Which brings me back to my own crazy mouse.

CORA: See, there's some two little beads - for you!

STANDEN: As a parent, there are ways that I could lower the chances that Cora will grow into a biter. When Mathews works with young kids, she does things like put Band-Aids on their fingers, to help them notice when they're biting or pulling. Then she'll, say, give them a sticker if they can go a whole day without doing it. I had started to do a clumsier version of this; gently batting Cora's hand away from her mouth, whenever she started to bite. But it had come at a price - one that I wasn't entirely comfortable with.

CORA: I'm going to stop doing it.

STANDEN: How come?

CORA: Um, 'cause you don't like me to, remember?

STANDEN: It was clear, I had to make up my mind. I had to decide what was worse - making Cora feel bad about herself, for something she couldn't help; or just letting her grow into a nail biter, which while certainly not the worst thing in the world, had given me some grief. And that is when I met someone who seemed to offer a third option.

DR. TRACY FOOSE: I am Tracy Foose, Dr. Tracy Foose.

STANDEN: Foose is a psychiatrist in San Francisco, who specializes in anxiety disorders. Like me, she has a 3-year-old daughter.

FOOSE: And I do bite my nails.

STANDEN: But Foose has a whole different take on this. Nail biting? It's just part of who she is. She is even sort of proud of it.

FOOSE: You know, my mom bites her nails. She was an artist. And so, I think I associate it with being cool and being older, and working on something important.

STANDEN: And then Foose tells me a story about a patient she met at the ER one night, when she was in her residency.

FOOSE: A lovely, middle-aged mother of several kids, who came in - and looked scared out of her wits.

STANDEN: This woman had become fixated on a perceived blemish on her face.

FOOSE: And she had picked at her cheek to a level where, she was bleeding profusely.

STANDEN: It was pathological grooming - dermatillomania, to be specific.

FOOSE: And she truly could not control herself despite the pain that it was causing, despite the disfigurement. And nail biting forever fell off my radar.

STANDEN: Nail biting is not life-threatening. On the scale of human failings, it barely lifts the needle - which isn't to say, Cora wouldn't be better off not biting her nails. But, says Foose, there may be another way to talk about it. Just as Foose had removed the stigma and the guilt for herself, maybe I could do that for my daughter.

FOOSE: You can go to the place of giving kids information - like, oh, I see you biting your nails. Mommy bites her nails, too. You know why we shouldn't bite our nails? 'Cause there are germs that live under our nails.

STANDEN: A way that frames it, in other words, as a choice. One that is hers to make - even if takes having her own kids one day, to make it.

For NPR News, I'm Amy Standen in San Francisco.