EVERYONE LOVES A fictional psychopath. Not simply the villains in almost every action film or television drama, but the antiheroes – the psychopaths we find ourselves rooting for.

We feel privileged when Frank Underwood takes us into his confidence in House of Cards. We are seduced by the protagonists in Tarantino and Hitchcock films.

We empathise with the talented Mr Tom Ripley. We are so fascinated by Kevin Khatchadourian that we feel the relentless need to talk about him.

Best of all is one of the most iconic culinary claims in cinematic history, namely Hannibal Lecter’s assertion (with regard to a census taker who once tried to test him) that he “ate his liver with some fava beans and a nice chianti”.

The cannibalistic psychiatrist then gratingly sucks air through his teeth, leaving us in no doubt that we are witnessing the darkest of psychopathic menace. And yet, somehow, we still like him.

Fascination

Our fascination does not end with fiction.

In 2014, millions of viewers tuned into Channel 4’s Psychopath Night to experience the chill of interviews with real-life serial killers.

Subsequently, over two million people took Professor Kevin Dutton’s online psychopath test, curious about their own levels of psychopathy.

Peruse the shelves of any bookshop and witness shelves strewn with true-crime paperbacks.

Meanwhile, the criminal trials of psychopathic killers (especially if they happen to be middle class) are guaranteed to fuel days, weeks or even months of media scrutiny and speculation.

Of course, psychopathy has nothing whatsoever to do with psychosis – a psychological state in which the mind becomes detached from reality.

Psychosis involves symptoms such as hallucinations (hearing or seeing things that aren’t there) and delusions (fervently believing things that aren’t true). People with psychosis are no more likely to be psychopaths than you or I.

So, what exactly is a psychopath? Perhaps the most agreed-upon means of determining this is Canadian psychologist Dr Robert Hare’s Psychopathy Checklist.

According to this inventory, a psychopath is a manipulative person who repeatedly engages in a wide range of irresponsible, unethical or criminal activities for personal gain.

He (for it is often a he) has a constant need for stimulation and lacks any realistic long term goals.

He lacks empathy or remorse and tends to blame others for his unscrupulous activities.

He will appear superficially charming, but also glib and shallow with a grandiose sense of self-worth.

Promiscuous sexual behaviour, many short-term marriages, adultery and so forth are common.

The psychopath will often lie to cover up his actions. Looking back, his childhood will likely involve early behavioural problems and juvenile delinquency.

While few psychopaths will tick all the boxes outlined, around 75% of the characteristics is enough to earn the label.

Mythology

The psychopath is nothing new to society. Around 300 years BC, Theophrastus – a student of Aristotle – wrote about psychopathic traits in a certain type of individual he named the “unscrupulous man”.

Greek and Roman mythology, the Bible and the plays of Shakespeare are filled with stories of individuals with psychopathic traits.

The 18th-century French psychiatrist Philippe Pinel described mania sans délire (insanity without delirium) as profound immorality and antisocial behaviour in individuals who are often highly intelligent and have no overt signs of mental illness.

Much debate followed, with psychiatry arguing that psychopathy itself was an illness, and the law strongly refuting this claim, citing the inappropriate medicalisation of criminal behaviour.

The term psychopastiche (psychopath) was first coined in 1888 by the German psychiatrist JLA Koch.

The term became rather overinclusive by the early part of the 20th century and seemed to include anyone vaguely abnormal.

The (now obsolete) concept of sociopathy emerged around this time to describe the superficially charming criminal with an antisocial personality disorder.

Broadly speaking, the consensus seemed to be that psychopaths were genetic and hence “born”, while sociopaths were “made” by adverse early experiences.

Enter the American psychiatrist Hervey Cleckley who, in his book The Mask of Sanity (1941), narrowed the definition of psychopathy to 16 characteristics. Hare’s Psychopathy Checklist was later based upon this.

Conservative estimates suggest there are 30 million psychopaths in the world – around one in 200 of us.

Up to 35% of the prison population are psychopaths but, contrary to popular belief, not all psychopaths are serial killers.

Indeed, many psychopaths function perfectly well in everyday life, sometimes with impressive careers as lawyers, politicians, estate agents, surgeons, and – yes – even the occasional psychiatrist.

Research

So, are psychopaths born or are they made? This is the theme of Lionel Shriver’s novel We Need to Talk about Kevin, in which a mother examines her conscience in the aftermath of her psychopathic teenage son’s a Columbine-style massacre at his American high school.

Since the early 1990s, functional magnetic resonance imaging (fMRI) studies have compared the brains of psychopaths and non-psychopaths.

Such research has highlighted functional differences in certain parts of the brain which process emotional memory and help us to profit from experience.

Some scientists hypothesise that these differences date back to an early developmental age, possibly even before birth.

The emerging consensus is that psychopaths have a deficit in emotional intelligence but otherwise normal IQ. Negative childhood experiences, it seems, can exacerbate this.

Even if we medicalise psychopathy, there is little current evidence that it can be treated. Many believe that the best way to limit a dangerous psychopath’s effect on society is simply to keep him away from it.

Not everyone agrees, however, and some recent projects involving intensive behavioural therapy have shown good results in juvenile detention centres in the United States.

A little too late perhaps for the likes of Frank Underwood, Tom Ripley and Hannibal Lecter, but then life would be so much duller without the fictional psychopath.

Dr Stephen McWilliams is a consultant psychiatrist and author.