Pathological Liars

"A difficulty is identifying pathological lying, or distinguishing it from or confusing it with a host of other disorders, notably antisocial personality disorder (APD), attention deficit hyperactive disorder (ADHD), obsessive compulsive disorder (OCD) and conduct disorder (CD.) CD and pathological lying are both often discovered during adolescence. Reich found that subjects who intentionally dissimulate (to conceal the truth rather than tell a lie) display other behaviors associated with antisocial and narcissistic personality disorders. Physicians believe all underlying conditions should be addressed before tackling the pathological lying."

From

http://www.ehow.com/about_5465090_psychology-research-methods-pathologic...

And
"What, then, amounts to “pathological” lying, and what distinguishes the pathological liar from the person who just lies a lot? Dike and colleagues1 suggest that the diagnosis is made when the lying is persistent, pervasive, disproportionate, and not motivated primarily by reward or other external factors. They also suggest, however, that a key characteristic of pathological lying may be its compulsive nature, with pathological liars “unable to control their lying,” although another term they use is “impulsive.” In addition, they refer to other accounts that speculate on whether the pathological liar may be unaware that he is lying,"

From:

http://www.jaapl.org/content/33/3/350.full

http://www.ehow.com/about_5465090_psychology-research-methods-pathologic...

http://www.usc.edu/uscnews/stories/11655.html