In today's generation, some people tend to lie on social media to earn praises from others. But then, when it becomes a habit, and you couldn't already control it, lying can be a sign of a mental health problem.

Candice Lam, a clinical pathologist at the Mindcare clinic in Central, Hong Kong, said compulsive or pathological lying is a mental illness in itself, or it can also be a symptom of mental illnesses including depression, anxiety, obsessive-compulsive disorder, as well as narcissistic personality disorder, as reported by the South China Morning Post.

She explained that the brain structure of pathological liars differs from normal people. Usually, normal people don't feel comfortable when telling lies as they believe it could have possible negative consequences. However, pathological liars aren't afraid to tell lies; they simply couldn't control their lying behavior.

In 2005, the University of Southern California conducted the first ever study in the world providing evidence of structural neurological differences in pathological liars, which was published in the British Journal of Psychiatry. At that time, researchers used magnetic resonance imaging to analyze the structural brain differences between liars and normal people. The results revealed liars' brains had white matter and slightly less grey matter compared to the control group.

Adrian Raine, a researcher involved in the study, said having white matter could likely give liars a tool to master the "art of deceit." For Lam, people tend to say "white lies" to avoid hurting another's feelings, yet it becomes evolutionary wherein some use it to avoid embarrassment or to look better in front of other people. She added there's still a clinical difference between lying for an external benefit and lying for internal reasons.

Lam explained lying driven by external factors weren't considered pathological, such as telling lies to gain money, sex, or power. For instance, a married man lies to a woman that he's single hoping to gain sex as a reward, or a child is lying about having done his homework to avoid punishment. These are simply driven by external desires.

 But lying for internal reason could be considered pathological. Lam said people tell lies as an act of self-aggrandizement - to make them feel good about themselves or to lie to gain more outside attention. They couldn't control their internal desires, and they become addicted to lying. And after years of self-deception, pathological liars will end up believing their lies and no longer aware there'ye telling untruths.

Lam noted pathological lying could be treated through cognitive behavioral therapy, wherein psychologists will initially identify the reason why the patient is lying. Then, they'll help them to cope with their problems and face reality. But while it can be treated, the prognosis remains hard as some people who have the condition won't seek mental help themselves.