If mental illness is the Cinderella of the broader health service, then personality disorder (PD) is the unloved princess of psychological health.
Individuals with PD often do not consider themselves to have a mental health problem, while mental health services may view individuals with personality disorders as complex and difficult.
While psychiatry in general lacks specific tests for various conditions, PD is even more acutely dependent on subjective assessment than illnesses such as depression and bipolar disorder. It may not be overly unkind to describe PD as the rag-bag of the speciality.
Personality refers to the pattern of thoughts, feelings and behaviour that makes each of us the individuals that we are. Mostly we tend to behave in fairly predictable ways, and can be described, accordingly, as being shy or selfish or outgoing.
Personality generally changes as we go through different experiences in life and learn to cope more effectively.
Limited range of emotions
Someone with a personality disorder, however, finds this change more difficult. They tend to have patterns of thinking, feeling and behaving that are more resistant to change; those affected generally have a more limited range of emotions, attitudes and behaviours with which to cope with everyday life.
This tends to set the person at odds with those around them, leading to stress for themselves and others.
The American Psychiatric Association describes 10 distinct PD types: paranoid, schizoid and schizotypal personality disorder; antisocial, borderline and histrionic personality disorders; and narcissistic, avoidant, dependent and obsessive-compulsive personality disorder.
The latest "bible" of psychiatric diagnoses, the 2013 version of the Diagnostic and Statistical Manual of Mental Disorders, is thought to have "pulled its punches" when a final draft of the section on personality disorders was approved. Initially it looked like PD would be evaluated on elements of a person's personality functioning (for example, identity, self-direction, empathy and intimacy) and on five sets of personality traits.
But at the last minute this was downgraded to a research section, and to the dismay of many psychiatrists, the older, more rigid approach to diagnosis was maintained.
How common are personality disorders? A 2008 study estimated about one in 10 people could be diagnosed with some type of PD. But it remains a controversial diagnosis: being labelled as PD is seen as judgmental and even personally insulting; it is sometimes associated with crime; and PD is associated with someone being dangerous and violent. In fact, a person with PD is more likely to harm themselves than others.
The cause of PD is unclear; there is some evidence to suggest that family circumstances can make you vulnerable to the condition. Many people diagnosed with borderline personality disorder report having been neglected, or physically or sexually abused as children.
No magic bullet
Whatever about classification of PD, there is no argument that the condition is a challenging one to treat. There is no magic bullet treatment in the form of medication; in addition, the very traits of some types of PD make it unlikely the person with these traits would consider themselves abnormal.
A number of talking therapies have shown some success with some forms of PD. Dialectical behaviour therapy can be effective in the treatment of borderline personality disorder. It teaches new skills to help the patient manage emotions, such as distress, and improve the way they interact with others. It helps change behaviours that cause the most problems so the person can deal better with day-to-day crises.
Cognitive behavioural therapy helps the person examine their usual pattern of thoughts and attitudes, allowing them challenge the ideas and beliefs that lead to problems; it seems to work best for people with dependant or avoidant PD.
And spare a thought for the partners and relatives who need support dealing with the unpredictable behaviours of those with the condition.