Personality, defined psychologically, is the set of enduring behavioral and mental traits that distinguish between individual humans. Hence, personality disorders are defined by experiences and behaviors that differ from societal norms and expectations. Those diagnosed with a personality disorder may experience difficulties in cognition, emotiveness, interpersonal functioning, or impulse control. In general, personality disorders are diagnosed in 40–60% of psychiatric patients, making them the most frequent of psychiatric diagnosis. A personality disorder is a chronic and pervasive mental disorder that affects thoughts, behaviors and interpersonal functioning. According to the Diagnostic and Statistical Manual-IV, a personality disorder is an "enduring pattern of inner experience and behavior that deviates markedly from the expectation of the individual's culture, is pervasive and inflexible, has an onset in adolescence or early adulthood, is stable.”