POPULAR culture typically portrays them as killers and psychopaths, but a psychiatrist at the frontline of work with personality disorder patients said decades of misunderstanding and underfunding must be reversed to tackle the huge toll of the condition on health and prison services.

Dr Andrea 'Andy' Williams, the Glasgow-based psychiatrist and psychotherapist leading research on behalf of the Royal College of Psychiatrist Scotland into the status of care for people with personality disorders in Scotland said the condition is "at the bottom of the list" as a mental health priority.

Dr Williams said: "Things are very slowly improving but there's difficulties dealing with personality disorders - it's quite complicated. There's still quite a variety of views among mental health staff about how much we've got to offer someone with those difficulties, and that leads to a sort of hopelessness."

While personality disorders of all types (there are around 10 variations) affect approximately 10 per cent of the general population in Scotland, among prisoners the rate is 66 per cent - around 5000 inmates.

Among male prisoners, the most common form is "antisocial personality disorder", or psychopathy, where offenders typically lack guilt, repeatedly break the law and are prone to rage. Extreme cases, which Dr Williams acknowledges the profession "still knows very little about" in terms of treatment, include serial killers such as Ted Bundy and cult leader Charles Manson.

It comes as the latest Hollywood take personality disorders sees James McAvoy star in 'Split' as a killer with multiple personalities, a condition Dr Williams said was "very uncommon" - with psychiatrists divided on whether it exists at all.

In contrast, "borderline" personality disorder - the most common form affecting one-two per cent of the general population - is becoming better understood and, potentially, treatable.

Frequent among female prisoners, it is characterised by extreme emotional volatility and unstable personal relationships. Around one in 10 sufferers will commit suicide, with high correlations of self-harm and homelessness.

Dr Williams said: "It's early days but there's quite a lot coming through now from neuroimaging studies that suggest it affects different areas of the brain responsible for managing emotions. There's a frontal part of the brain that we use to understand interactions with other people - facial expressions, the emotional tone in someone else's voice. Most of us can manage that quite well but for people with borderline personality disorder, their trigger to becoming upset and annoyed is in that sort of misunderstanding - and their trigger point is low compared to the rest of us. Their mind and their ability to manage that emotional arousal is impaired, and their reaction is big.

"For the person themself, it usually means a very chaotic life - lots of difficulties managing work, relationships, family, all areas of life tend to be affected by it. It's a very serious condition."

Research points to a combination of genetic factors and environmental triggers, particularly neglect and instability in infancy and early childhood - such as moving between multiple care settings - when the brain is developing its capacity to manage emotions and form "attachments" to loved ones.

Unlike conditions such as depression or schizophrenia, there are no drugs for personality disorders, and promising new counselling therapies for "borderline" patients require long-term - and therefore costlier - interventions. However, early indications suggest they work, with trials in England testing whether they could also help patients with milder antisocial personality disorder.

Dr Williams will present her findings on the state of care in Scotland at a conference in Inverness in March.

She said: "My point is always that these people keep turning up and they will continue to turn up - at accident and emergency and in prison. They're not going to go away and I think we should get better at diagnosing it and realising that, yes, we do have therapies."