Someone who lies constantly is most commonly called a pathological liar or a compulsive liar. These are the two terms you’ll hear most often, and while people use them interchangeably in everyday conversation, they describe slightly different patterns. The clinical term, used in psychology since the early 1900s, is pseudologia fantastica.
Pathological Liar vs. Compulsive Liar
A pathological liar tells lies repeatedly over a long period, often without a clear external motive. The lies aren’t necessarily designed to get something specific, like money or a promotion. Instead, the lying becomes a deeply ingrained pattern, sometimes so automatic that the person seems unable to stop even when the truth would serve them better. Pathological lying is defined clinically as a long-term practice of systematic, repeated deception that has no expressed psychological motive or external benefit.
A compulsive liar, on the other hand, lies out of habit or impulse. The lying feels driven, almost reflexive, similar to other compulsive behaviors. Compulsive lying can show up as a symptom of several underlying conditions, including ADHD, bipolar disorder, impulse control problems, substance dependency, and certain personality disorders.
In practice, the line between these two categories is blurry. Many people who lie constantly show features of both. The key distinction from ordinary lying is this: most people lie strategically, to achieve a goal or avoid a consequence. Pathological and compulsive liars often lie when there’s no obvious reason to, and the behavior persists even when it damages their relationships and reputation.
How Common Is Pathological Lying?
More common than you might expect. Research published in Psychiatric Research and Clinical Practice estimated that pathological lying has a prevalence of 8% to 13% in the general population. That range accounts for people who self-identified as pathological liars (13%) and those who met stricter criteria involving personal distress from their lying (8%). Either way, it’s not rare.
Everyone lies occasionally. Studies on everyday deception consistently show that most people tell small, social lies regularly. What separates a pathological liar is the frequency, persistence, and seeming inability to control the behavior, even when it creates serious problems.
What’s Happening in the Brain
There’s evidence that chronic liars have measurable structural differences in their brains. A study published in The British Journal of Psychiatry found that pathological liars had 22% more connective wiring (white matter) in the front part of the brain compared to people who didn’t lie pathologically. They also had significantly less grey matter in the same region.
White matter helps different brain areas communicate quickly. More of it in the prefrontal cortex, the area responsible for planning and decision-making, may make it easier for someone to weave together complex, convincing stories on the fly. Less grey matter, which handles impulse control and moral reasoning, could help explain why the urge to lie goes unchecked. This doesn’t mean pathological liars are “born that way” with certainty, but it does suggest the behavior has a biological component, not just a moral one.
Conditions Linked to Chronic Lying
Pathological lying is not currently listed as its own diagnosis in the DSM, the standard manual used to classify mental health conditions. It appears only as a non-essential symptom of factitious disorder (formerly called Munchausen syndrome), a condition where someone fabricates or induces illness in themselves to receive medical attention. Some clinicians have argued for decades that it deserves its own diagnostic category, but it hasn’t happened yet.
Instead, chronic lying tends to show up as a feature of several personality disorders:
- Antisocial personality disorder (ASPD): Lying here is often strategic, aimed at exploiting or manipulating others. People with ASPD typically have a history of conduct problems going back to childhood.
- Narcissistic personality disorder (NPD): Lies often serve to inflate the person’s image, maintain control, or avoid accountability.
- Borderline personality disorder (BPD): Lying can become a way to avoid perceived rejection or abandonment. The deception is often driven by intense fear rather than calculated self-interest.
- Histrionic personality disorder: Exaggeration and dramatic storytelling blur into dishonesty as the person seeks attention and emotional reactions.
Compulsive lying also appears alongside bipolar disorder, ADHD, and substance use disorders, where impulsivity and poor self-regulation play a role.
How to Recognize the Pattern
The difference between someone who lies a lot and a pathological liar comes down to a few patterns. Pathological liars tell stories that are often elaborate and internally detailed. They may mix in enough true information to make the lies convincing. When confronted, they typically double down, revise the story, or act offended rather than admitting the deception.
Over time, their stories contradict each other. You might notice that the same event gets retold with different details depending on the audience, or that their version of events doesn’t match what other people witnessed. The lies also tend to serve no clear purpose. Someone lying to avoid getting fired makes strategic sense. Someone lying about what they had for lunch does not, and that kind of unnecessary dishonesty is a hallmark of pathological lying.
Another telling sign is the reaction when caught. Most people feel embarrassed or guilty. A pathological liar may show very little distress, quickly pivot to a new version of events, or turn the confrontation into an argument about something else entirely.
Living With or Around a Chronic Liar
If someone in your life lies constantly, the most practical approach is reducing opportunities for deception. Ask direct, specific questions that require yes or no answers rather than open-ended ones that invite elaborate narratives. Keep records when it matters: emails, texts, written confirmations. This isn’t about catching them in lies for sport. It’s about protecting yourself from the real consequences that chronic dishonesty creates.
With a narcissistic liar specifically, experts recommend keeping interactions logical and low-drama. These individuals often thrive on the chaos their lies generate. Responding calmly and sticking to verifiable facts removes the emotional fuel they’re looking for. Setting up accountability structures, like having multiple people involved in important decisions or agreements, limits how much damage any single lie can do.
It’s also worth understanding that you cannot fix this behavior through confrontation alone. Pathological lying is deeply entrenched, often tied to personality structure or underlying mental health conditions, and it typically requires professional treatment. Therapy that addresses the root cause, whether that’s a personality disorder, trauma, or impulse control, is the most effective path. But the person has to want to change, and many chronic liars don’t see their behavior as a problem, which makes treatment one of the more difficult challenges in mental health care.