What is a personality disorder?

When we talk about personality, we are talking about the way we think and feel about ourselves and others and how this influences the ways we act and experience the world over our lifetime. Personality may be formally defined as 'individual differences in characteristic patterns of thinking, feeling and behaving which tend to be stable over time'.

A personality disorder, as defined by the 5th edition of the Diagnostic and Statistics Manual (DSM) as 'an enduring pattern of inner experience and behaviour that deviates markedly from the expectations of the individual’s culture'. This 'enduring pattern' is described as being inflexible and pervasive across a broad range of social situations, leading to clinically significant distress or impairment in social, occupational, or other important areas of functioning.

We might have a personality disorder if we have experienced significant difficulties with our emotions, thoughts and behaviours, often since adolescence or early adulthood, which cause us a lot of distress and ongoing trouble with many of our relationships. We may also experience difficulty in our ability to manage day-to-day activities, as well as falling short of reaching our personal, academic or vocational goals. A personality disorder can be identified by looking at the way we perceive and understand ourselves and others. Similarly, how we respond to certain situations, how we relate to other people around us and the ways we experience our impulses and urges, can also help us identify if we have a personality disorder.

Only an accredited mental health specialist, such as a clinical psychologist or psychiatrist, can make a formal diagnosis of personality disorder. A diagnosis of personality disorder requires a robust and comprehensive assessment process.

There are two manuals that are used to decide if someone is or isn’t living with a personality disorder — the Diagnostic and Statistical Manual of Mental Disorders (DSM) and the International Classification of Diseases (ICD). The DSM categorises personality disorder using ten different, often overlapping personality disorder sub-categories. The ICD doesn’t use this categorical system but instead offers a general description of personality disorder, classifying severity as mild, moderate and severe.

One of the personality disorder sub-categories in the DSM is 'borderline personality disorder'. Historically, the term ‘borderline’ was chosen to define what psychiatrists at the time perceived as a person being 'right on the border' of what they called 'neuroses' and 'psychosis'. We have since come to understand that this is an inappropriate description, with the term itself regarded by many as stigmatising and unhelpful. While classifications for different subtypes of personality disorder were abolished in the most recent version of the ICD, the ICD has retained a ‘qualifier’ for what it calls a 'borderline pattern'. This helps to identify which evidence-based therapies are most suitable to offer people who would otherwise have a diagnosis of BPD under the DSM.