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Are you a hair-twirler or nail-biter?

Call it a nervous habit or tic, almost everybody has at least one - whether they are aware of it or not

Kate Murphy | NYT 

Nail-biter. Photo: iStock
Photo: iStock

Are you a toe-tapper, hair-twirler, eye-blinker, head-nodder, nail-biter, knuckle-cracker, skin-picker, lip-licker, shoulder-shrugger or a chin-stroker?

Call it a or tic, almost everybody has at least one — whether they are aware of it or not.

Tics exist on a spectrum ranging from barely noticeable to extremely annoying to poten-tially injurious.

While research has focused mostly on the more severe forms associated with neurobehavioural disorders such as Tourette syndrome and autism, there’s a growing realisation of the pervasiveness of so-called repetitive, nonfunctional motor behaviours and that the degree to which you engage in them is a barometer of your peace of mind.

“Our stressful society definitely brings it out more,” said Alon Mogilner, a neurosurgeon at New York University Langone Medical Center. “It’s a delicate balance within the circuitry of the brain so you are able to tamp down on things you don’t want to do.”

Experts divide repetitive, nonfunctional motor behaviours into three overlapping, and not always agreed upon, categories. First, there are classic tics, which typically involve quick, jerky motions of the head, neck or arms preceded by an urge, akin to an itch that needs to be scratched. Tics can also be phonic such as grunting, throat-clearing or sniffing.

Next are stereotypies (pronounced steer-ee-AH-ta-peez), which usually don’t have a premonitory feeling and are more fluid and rhythmic like body rocking, finger drumming and leg bobbing. Lastly, there are body focused repetitive behaviours, which are essentially grooming gone awry like compulsive nail-biting, hair-pulling and skin-picking.

All of these behaviours are what experts call “unvoluntary,” as opposed to an involuntary muscle twitch or tremor. You can stop the tic or motor habit when asked to or when distracted but the problem is, sooner or later, you go back to doing it. In some circumstances the behaviour is distressing to the person, particularly if it is injurious or embarrassing, but more often the movement or mannerism is just maddening to those in proximity.

“If we dive into the research and look at disordered, unwanted repetitive behaviours as well as nonclinical, non-impairing repetitive behaviours, they all involve the region of the brain called the basal ganglia, which is involved in motor control,” said Ali Mattu, a clinical psychologist who specialises in body focused repetitive behaviours at Columbia University Medical Center.

Though still poorly understood, the basal ganglia are sort of like the movement command center of the brain that responds to situations by choosing from a menu of motions or gestures that you’ve learned. The theory is that when situations are frustrating or stressful because you are either over- or under-stimulated (i.e. strung out or bored) your basal ganglia manage by selecting (or perhaps failing to inhibit) a default motor behaviour, which would be the tic, stereotypy or motor habit.

In this way, we are not so different from animals. Go to many zoos and you’ll see anxious or bored animals rocking, jerking their heads and necks, plucking out their feathers or fur, pacing in circles, swinging their arms (or trunks in the case of elephants) and mouthing themselves or various objects.

“The whole point of a habit is you don’t have to use cognitive resources to do it,” said Doug Woods, a professor of psychology at Marquette University in Milwaukee who studies and treats people with tics and other repetitive behaviours. He said that for many of his patients, the tics somehow become associated with a reward — whether it’s temporary distraction, satisfaction or release.

Most repetitive behaviours, regardless of etiology, begin in childhood. The immature brain, unable to recognise and process emotions as an adult does, resorts to motor activity to cope. Except for children with severe autism, most kids grow out of habits like head-shaking, arm-flapping and grimacing as they become better able to understand and manage their feelings. Or they just find a way to convert the behaviour into something more socially acceptable and “adult.” Rocking might morph into leg-bobbing, mouth-stretching turns into gum-chewing or finger-wiggling may become iPhone-fiddling (yet another reason people can’t put down their phones).

“These behaviours persist, it’s just the person learns to have more control over it or learns to do it in private or under the table,” said Harvey Singer, professor of neurology at Johns Hopkins School of Medicine and specialist in childhood stereotypies.

© 2017 The New York Times

First Published: Fri, September 15 2017. 23:14 IST