Psychology › Mental health & disorders › Mental disorders: what they are and how common
Personality disorders
· Condition or disorder
Mixed evidenceSome support; effects smaller or less consistent than once thought.
Long-lasting, rigid patterns of thinking, feeling and relating that cause distress or problems across many areas of life.
See it on the Psychology map →What it says
DSM-5 lists ten types in three clusters: odd (paranoid, schizoid, schizotypal), dramatic (antisocial, borderline, histrionic, narcissistic) and anxious (avoidant, dependent, obsessive-compulsive). Roughly one in ten adults may meet criteria for one; estimates vary. The types overlap heavily and diagnoses are unreliable, so the WHO's ICD-11 (2022) replaced them with a severity rating plus trait descriptions. Once thought untreatable, borderline personality disorder responds to dialectical behavior therapy, and most patients improve over a decade.
Why it matters
These patterns shape careers, marriages and conflicts. The shift from fixed labels toward measurable traits mirrors a broader change in how psychiatry sorts problems.
The evidence
Population surveys, Mary Zanarini's ten-year McLean Hospital follow-up showing most borderline patients remit, and controlled trials of Marsha Linehan's dialectical behavior therapy, beginning in 1991.
Open questions
Whether personality disorders are distinct conditions or extreme ends of ordinary traits is the central debate; 'narcissist' and 'psychopath' are often misused as insults.
Connections (3)
▸Personality disorders are increasingly described with The Big Five personality traitsMixed evidence
The connection
Most personality disorders look like extreme, rigid versions of normal traits: borderline maps to very high neuroticism, antisocial to low agreeableness and conscientiousness, avoidant to high neuroticism and introversion. ICD-11 (2022) and DSM-5's alternative model describe people by severity plus trait domains closely resembling the Big Five.
Who showed it and when
Proposed by Thomas Widiger, Paul Costa and colleagues from the 1990s; adopted in DSM-5's alternative model (2013) and the WHO's ICD-11 (2022).
How solid is it?
Meta-analyses show each disorder has a fairly consistent Big Five profile, and trait models predict functioning at least as well as categories.
Open questions
Clinicians find labels like 'borderline' useful shorthand, and how to carry decades of category-based research and treatment into a trait system is contested.
▸Personality disorders form a debated category of Mental disorders: what they are and how commonMixed evidence
The connection
Unlike episodes of depression or panic, personality disorders describe lasting ways of being, which is why DSM-III (1980) put them on a separate 'axis'. DSM-5 folded them back in with other disorders and kept the ten types, while offering an alternative trait-based model.
Who showed it and when
DSM-III's multiaxial system (1980–2013) put personality disorders on Axis II; DSM-5 dropped the axes in 2013.
How solid is it?
Studies show personality disorders often co-occur with other disorders and that their symptoms change more over time than the 'lasting' definition implied.
Open questions
Whether they are illnesses, extremes of normal traits, or labels for difficult behavior, and how stigma affects care, are debated.
▸Dialectical behavior therapy (DBT) was designed for borderline, one of the Personality disordersWell replicated
The connection
Linehan saw borderline personality disorder, marked by intense mood swings, unstable relationships and self-harm, as mainly a problem of regulating emotion. Standard CBT felt invalidating to these patients, who often quit. DBT added acceptance and validation to change strategies and taught concrete emotion skills.
Who showed it and when
Developed at the University of Washington in the 1980s and published in 1993; now used in clinics worldwide, including adaptations for adolescents.
The evidence
Randomized trials and a 2020 Cochrane review show DBT reduces self-harm and improves functioning in borderline personality disorder; it is the condition's most studied therapy.
Open questions
Other approaches, such as mentalization-based therapy and schema therapy, also work; it is unclear whether DBT is better or simply better studied.