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

© The Conversation