Yvonne Roberts: 'I want' is the slogan of our age

Jude Law has as much chance of sticking to the six commandments dictated by his newly reinstated girl friend, Sienna Miller, as a large slice of humanity has had in adhering to the ten presented by Moses. According to the "source close to Ms Miller", who appears never to leave her side for nanosecond, Law must stay faithful; he must stop spending time with his ex-wife; he must stop asking Sienna for her hand; he must make Ms Miller fall in love with him all over again; he must control his temper; he must let her make her own career decisions and he must not stop her seeing her friends.

It's the "musts" that give it away - as does the graphic picture presented in the press of a controlling, possessive, cheating individual who doesn't appear to know what he wants - until it's in danger of slipping away. If Sienna sees Law in the same way as do the gossip columnists, instead of taking him back, she might have done better to have given "the ambassador of narcissism", Sam Vaknin, an Israeli-born writer and businessman, a call.

Vaknin, a self-confessed narcissist, once imprisoned for fraud, is the author of Malignant Self Love, Narcissism Revisited, allegedly one of the most requested books in the British Library, which - as a narcissist would - he vigorously plugs at every opportunity on his website.

Narcissism is big in the USA. Its diagnosis and treatment has spawned a multitude of support groups for those affected by narcissists (usually women who believe they have fallen for a "jack the lad" only to discover someone far darker; more manipulative and no fun at all) as well as a lucrative stream of books.

Freud was the first to discuss narcissism. Only much later in the 1990s, did the American Psychiatric Association give it a definition. In The Diagnostic and Statistical Manual of Mental Health Disorders, narcissistic personality disorder (NPD) is described as, "an all pervasive pattern of grandiosity (in fantasy or behaviour); a need for admiration or adulation and a lack of empathy, usually beginning by early adulthood and present in various contexts." And incurable. In the UK, many professionals view NPD with caution - not least because its "symptoms" are so all embracing they could describe large swathes of the population. (In the Sixties, the common slogan was "All men are bastards" - now for those in know, fairly or unfairly, it's "All men are narcissistic bastards".)

Of course, it's a matter of degree and how all-controlling the narcissistic behaviour becomes. Aspects of it do give a troubling glimpse of the corrosive effect of the toxic mix of consumerism; individualism; selfishness and the pressures of work on relationships and family life - and that's a concern to us all that goes far beyond Jude and Sienna and Cupid's broken bow.

In June this year, Brian Blackwell, aged 18, was convicted of murdering his parents Brian and Jackie, in a narcissistic rage because they had questioned his spending habits. He then went on a £30,000 spending spree with his unwitting girlfriend. He had fed her fantasies about his alleged abilities as an international tennis player. He was diagnosed with narcissistic personality disorder. Murder is the extreme end of the NPD spectrum but even in its mildest form, it is something far more than destructive than simple self-love.

The American Psychiatric Association has nine diagnostic criteria of which at least five have to be identified to merit the label NPD. Vaknin boils these down to a handy set of "don't do" tips for women who just can't stay away from a narcissist - never contradict; never offer intimacy; never expect empathy - narcissists don't do empathy; never point out his mistakes or inadequacies however constructively; never suggest you have a life of your own. Above all, offer admiration and adulation constantly and never expect an uncomplicatedly good time. In short, don't expect life to be a barrel-full of laughs which, for some, is precisely the attraction.

Jude Law, of course, may be a million miles way from NPD. His only fault may be that he's head over heels in love. Still, it's when we come to the effects of NPD on children that a truth begins to emerge about the state of some family lives and why NPD is termed the mental epidemic of the 21st century.

In the myth, Narcissus falls in love with his own reflection and pines away. In the legend, Echo also loves Narcissus but she has no voice of her own, she can only repeat the words of others. When he says to himself, "I love you". She repeats what she hears with meaning - but she goes unheard.

Children with narcissistic parents are "Echo" - they often also suffer as a result of adult self-absorption. In the United States, recognition of the casualties of narcissistic families, is relatively recent. Unlike the visibly dysfunctional families, often blighted by poverty, and constantly maligned by politicians -narcissistic families are well disguised as "normal" loving units that, nevertheless, can also produce children whose adult behaviour is equally costly to society - in terms of addiction, abuse and relationship breakdown.

It is easy to pathologise every aspect of life in a society that increasingly treats happiness as a shopper's "right". Reading through some of the case histories of children reared by narcissistic grown-ups strikes an ominous chord.

Beth, for instance, describes how her mother was always "there" at home - but never engaged; never listening so Beth felt worthless, unlovable and invisible - made plain in destructive adult behaviour . "I know she loved me, but it was like trying to grab smoke - you see it, but you can't get it into your hand. I still feel that way."

Therapists Stephanie and Robert Pressman in The Narcissistic Family, argue that narcissistic parents for whatever reason - alcoholism; mental illness; job stress, lack of parenting skills - are primarily involved in getting their own needs met. Their children soon learn only to react and reflect those needs; they fail to develop trust in their own feelings and eventually teach themselves to have few feelings at all. They become Little Sir Echos.

They live in the expectation that they will fail; they avoid intimacy; they may self-destruct - not out of love for themselves but out of hatred. "They couldn't bear for us to be anything but cardboard cut-outs of successful children," said one 31-year-old male now unable to sustain relationships.

Narcissism seems to be the devil child of the 1980s yuppie Thatcherite "Me" decade. "I want" is the slogan of our times. Perhaps that's the moral of the tale in the Jude and Sienna saga - when we confuse "I love" with "I want", in one way or another, like Narcissus, we're doomed