Pathological liars will often lie for no reason at all--even if it means that the lie puts themselves in danger. Pathological liars may be suffering from a mental illness such as bipolar disorder or addiction (i.e., drugs or alcohol). They may tell stories that are quite unbelievable, or they may make their own lives sound too good to be true. The stories they tell may change. They may thrive on being the center of attention, and their friends and family members may warn you about the compulsive lying. When you question a pathological liar, he may become defensive and won’t admit to his lies.