As one of my Hong Kong patients says: 'Cutting creates physical pain from emotional pain - which is easier to deal with.'

Some even describe a sense of euphoria. 'It feels good,' says another patient. 'There's something exciting about it.'

Jadis Blurton, clinical director of Therapy Associates in Central, says: 'The good news is that it's not typically a suicidal gesture, although it certainly looks like one'.

Studies consistently show that women are more prone to self-harm than men.

'Men act out - women act out by acting in,' says Dusty Miller, author of Women Who Hurt Themselves: A Book of Hope and Understanding. Because many women don't express anger externally, when they do experience rage, they tend to turn it on themselves, she says.

Based on a 1986 survey, Armando Favazza and Karen Conterio developed a profile of the typical self-injurer.

She is female (97 per cent of respondents), in her mid-20s to early 30s, and has engaged in this kind of behaviour since adolescence. She tends to be middle or upper-middle class, intelligent and well educated. She has a higher likelihood of coming from a background of physical and/or sexual abuse, or from a home with at least one alcoholic parent.

Eating disorders are also often reported in this group. Methods of inflicting pain include cutting, hitting, burning, head banging, breaking bones and preventing wounds healing. According to recent estimates, 1-3 per cent of America's population of about 280 million people have injured themselves.

Although many people use more than one method, studies show that cutting wrists, upper arms and inner thighs are the most popular means.

Some researchers say cutting provides relief from overwhelming anxiety, fear or sadness in a person's life. Self-harm is often the only coping mechanism they know. Of course, in the long term, it creates more problems - such as feelings of inadequacy and failure, a loss of control, embarrassment and physical injury.

In a study by Ulrich Sachsse and colleagues, published in the American Journal of Psychiatry (2002), the nightly cortisol levels (the stress hormone) in a woman who harmed herself were tracked. They were significantly lower on the days she harmed herself than on the days she didn't, the stress having been relieved by the abuse.

At times, these acts may divert attention from issues too painful to address, so the focus narrows to the act itself. Similarly, some describe their actions as a way of escaping depression and feelings of emptiness or numbness. And, like my patient, many get a sense of euphoria from harming themselves.

This makes sense, given that the body releases a hormone called endorphin, which is a natural opiate, in response to pain. Endorphins are responsible for what's called the runner's high.

It's well established that this same hormone is released as a result of vomiting, which may partly explain the addictive nature of those suffering from the eating disorder bulimia.

For many, self-harm is a way to relieve anger they can't express otherwise. Or, it may be a way of punishing themselves. For others, it's about control - that is, exerting control over their bodies or the behaviour of others.

A commonly held belief is that self-harm is a way to get attention, but this is an oversimplification, because many people choose to harm themselves in places where people can't see their injuries.

Nevertheless, for some it represents a desperate need to communicate with others the extent of their inner turmoil or their need for support. Self-harm can become a means of expressing feelings of alienation. In addition, it may be a continuation of abuse.

Childhood abuse leaves a sense of guilt in the survivor, especially if it happened at an early age. The victim can't understand why they were punished and, as a result, concludes that there is something inherently wrong with them.

Self-harm can become a way of continuing the punishment.

In an article in The Journal of Clinical Psychology (2000), the authors said that people who deliberately injured themselves usually had failed to develop three important self-capacities: the ability to tolerate strong emotion; the ability to maintain a sense of self-worth; and the ability to maintain a sense of connection to others.

'The development of a healthy sense of self worth is impaired when strong feelings are met with punishment or the suggestion that such feelings are unacceptable,' they wrote.

'The ability to maintain a sense of oneself as a person of worth can't be developed when a child never feels she is good enough or when her accomplishments are either not acknowledged or met with abusive words or actions.'

In a study in the Journal of Abnormal Psychology in 1995, groups of self-injuring and non-self-injuring people were led through guided imagery sessions in which each experienced the same four scenarios: a scene in which aggression was imagined; a neutral scene; a scene of accidental injury; and one in which self-injury was imagined. During the guided imagery sessions, physiological arousal and subjective arousal were measured. The results provide strong evidence that self-injury provides a quick, effective release of physiological tension, which would include that brought on by overwhelming psychological stress.

Reactions across groups were similar on the aggression, accident and neutral scripts. However, during the self-injury script, the control groups went to a high level of arousal where they remained, despite relaxation instructions. In contrast, self-injurers initially experienced increased arousal until the decision to self-injure was made, at which point their tension dropped.

As a result, the researchers suggested that self-injury could be a preferred coping mechanism because it quickly calmed the body, even though people who injured themselves often have negative feelings after an episode. But, although they may feel bad, the overwhelming psycho-physiological pressure and tension has been relieved.

So what do you do if you know, or suspect, your teenager or a friend is engaging in self-harm?

'Parents and professionals usually react with shock, dismay, fear and anger,' Blurton says. 'But it's important to remain as calm as possible and to be non-judgmental.

'Many kids try it only once. But for those who do it more often, it can become an extremely hard habit to break. One book I find helpful with teenagers and their parents is A Bright Red Scream: Self-Mutilation and the Language of Pain.

'This book helps them to realise they're not alone, and helps their parents to recognise and understand the emotions behind it.'

Sandra Comer is a Hong Kong-based psychologist