People with personality disorders often use language differently – our research reveals how

Is it possible to spot personality dysfunction from someone’s everyday word use? My colleagues and I have conducted research that suggests you can, and often sooner than you might expect.

Whether in a quick text message, a long email, a casual chat with a friend, or a comment online, the words people choose quietly reveal deeper patterns in how they think, feel, and relate to others.

Everyone has personality traits – habitual ways of thinking, feeling and behaving. When these patterns become rigid, intense or disruptive, they can cause ongoing problems with emotions, sense of self and relationships.

At the more severe end are personality disorders, where these patterns create significant distress and impairment. Common personality disorders include narcissistic, antisocial, and borderline personality disorder.

But not everybody has a full-blown disorder. Personality functioning actually exists on a spectrum. We’re all a little narcissistic, after all.

Many people you meet – at work, when dating, or online – may show milder difficulties, such as mood fluctuations, negativity, rigid thinking or darker traits like manipulation and callousness. These patterns often slip into how people speak or write long before they show up in more explicit behaviour.

There are some extreme examples. Linguists analysing the personal letters of Austrian serial killer Jack Unterweger – widely viewed as a classic case of malignant narcissism – found unusually high levels of self-focused language, such as “I” and “me”. He also had a notably flat emotional tone. Likewise, letters from Dennis Rader, the BTK killer (bind, torture, kill) displayed strikingly grandiose, detached and dominance-focused wording.

Psychologists have long known that certain linguistic habits reveal how people are functioning internally. For example, people experiencing distress consistently use more self-focused language and more negative emotion words. That’s because they internalise a lot and experience negative affect.

Those with darker personality traits often use more hostile, negative and disconnected language, including more swear words and anger words, such as “hate” or “mad”. At the same time, they use fewer socially connected terms like “we”.

Vitally, these patterns aren’t usually deliberate. They emerge naturally because language tracks attention, emotion and thought. With computational text analysis, researchers can now analyse these subtle cues at scale, and rapidly.

Our research findings

Across four studies using computational text analysis – three of which formed my PhD research – my colleagues and I found clear evidence that personality dysfunction leaves a detectable trace in everyday communication.

In one study of 530 people, published in the Journal of Personality Disorders, we analysed written essays about peoples’ close relationships. We also collected data on their levels of personality dysfunction. Those with greater personality dysfunction used language that carried a sense of urgency and self-focus – “I need…”, “I have to…”, “I am…”.

This was expressed alongside ruminative, past-tense wording. They also had more negative, particularly angry, emotion terms, such as “furious” and “annoyed”. At the same time, they used noticeably less intimate or affiliative language such as “we”, “love” and “family”.

In a second project, published in Journal of Affective Disorders Reports, we again analysed written essays (530 people), as well as transcribed conversations from 64 romantic couples which included women with diagnosed personality disorders.

Across both written and spoken communication, those with more dysfunctional or disordered personalities used more negative emotion words – and a wider variety of them. Even during mundane conversations, their language carried heavier negative affect, indicating a preoccupation with negative feelings.

Turning to online communication, in a study recently published in npj Mental Health Research, we analysed nearly 67,000 Reddit posts from 992 people who self-identified as having a personality disorder. Those who frequently engaged in self-harm used language that was markedly more negative and constricted.

Their posts contained more self-focused language and more negations – such as “can’t”. They also used more sadness and anger terms, and more swearing, while referencing other people less. Their wording was also more absolutist, reflecting all-or-nothing thinking, favouring words like “always”, “never”, or “completely”.

Together, these features created a linguistic picture of emotional overwhelm, negativity, withdrawal and rigid thinking.

Finally, in an ongoing project analysing more than 830,000 posts from the same 992 individuals with personality disorder, plus 1.3 million posts from a general-population comparison group of 945 people, we examined how people express their self-beliefs (“I am …”, “I feel …”, “My …”). Using an advanced self-belief classification tool, we found that people with personality disorders shared self-beliefs on online discussion forums far more often, and their wording differed profoundly.

Their self-beliefs were more negative, extreme, and disorder-focused, including phrases like “my mental health”, “symptoms”, “diagnosis” and “medication”. They also used more emotional descriptors such as “depressive”, “suicidal” and “panic”. Many self-belief statements centred on pain and trauma – “abusive”, “abandonment”, “hurt”, “suffer”.

They also frequently referenced childhood or significant relationships (“mother”, “partner”, “relationship”). These patterns arose across a wide range of discussion contexts, suggesting that deeper struggles with identity may surface in language universally.

Why this matters

Understanding these linguistic patterns isn’t about diagnosing people from their texts. It is about noticing shifts in language that can provide gentle clues. If someone’s messages suddenly become unusually urgent or extreme, emotionally negative, absolutist, inward-focused and socially detached, it may be a sign they’re struggling.

And in everyday situations – dating, befriending, online interactions – recognising patterns of hostility, extreme negativity, and emotional and cognitive rigidity can help people spot early red flags. This is particularly for dark personality styles, such as psychopathy or narcissism. For instance, noticeably high use of self-references (“I”, “me”), anger words (“hate”, “angry”), and swear words, combined with a lack of terminology indicative of social connection (“we”, “us”, “our”), may be important language patterns to look out for.

But no single word or phrase reveals someone’s personality. People vent, joke, and use sarcasm. What really matters is the pattern over time; the emotional tone, themes and recurring linguistic habits. Subtle linguistic traces can offer a window into someone’s emotional world, identity, thinking patterns and relationships long before they speak openly about their difficulties.

Noticing these patterns can help us learn about and understand others, support those who may be struggling, and navigate our social lives safely – online and offline – with greater awareness.

Charlotte Entwistle has received funding from the Engineering and Physical Sciences Research Council (EPSRC) and Leverhulme Trust.