Borderline Borderline (I) When used of mental ability it is usually defined as an IQ score of between 70 and 80. (2) In clinical psychology it is sometimes used to describe someone whose emotional disturbance appears to be more severe than NEUROSIS but is not quite psychosis.
Borderline Personality Disorder Borderline Personality Disorder is a mental illness marked by a pattern of unstable personal relationships and self image, as well as