[Impulsivity and mental disorders]

Although there are several studies revealing the role of impulsivity in mental disorders, debates in the literature about how to define and determine impulsivity continue. Being a measurable feature of behaviour, impulsivity is defined as the failure to resist a drive or stimulus or as a personality dimension as the inability to resist the desire to harm one's self or others. Besides this negative definition, however, impulsivity is also defined as independent dysfunctional and functional concepts having both positive and negative consequences. It can be a psychopathological structural part of many mental disorders, but it can be a characteristic of normal behaviour as well. Although not defined in detail in DSM-IV, it is mentioned as a diagnostic criterion in several mental disorders like impulse control disorders (pathological gambling, intermittent explosive disorder, pyromania, kleptomania and trichotillomania), impulsive aggressive disorders of personality (borderline, antisocial, histrionic and narcissistic), manic episodes of bipolar disorder, attention deficit hyperactivity disorder (ADHD), neurological disorders with behavioural disinhibition and substance abuse. Studies have revealed impulsivity to be more common in subjects with conduct disorders, attention deficit hyperactivity disorder, disorders of personality, substance and alcohol abuse, psychotic disorders, bipolar disorders, eating disorders and dementia compared to healthy subjects in control groups. The aim of the present paper is to define impulsivity as a concept and symptom, to discuss its relation to mental disorders, to show the biological basis of this relationship and to review the literature relating to this issue.