about 6% in primary care sett ings, about 10% among individual s seen in outpatient mental
health clinics, and about 20% among psychiat ric inpatients. The prevalence of borderline
personality disorder may decrease in older age groups. 
Development and Course
There is considerable variability in the course of borderline personality disorder. The most
common pattern is one of chronic instability in early adulthoo d, with episodes of serious
affective and impulsive dyscontrol and high levels of use of health and mental health re-
sources. The impairment from the disorder and the risk of suicide are greatest in the
young-adult years and gradually wane with advancing age. Although the tendency to-
ward intense emotions, impulsivity, and intens ity in relationships is often lifelong, indi-
viduals who engage in therapeutic interv ention often show improvement beginning
sometime during the first year. During their 30s and 40s, the majority of individuals with
this disorder attain greater stability in their relationships and vocational functioning. Fol-
low-up studies of individuals identified thr ough outpatient mental health clinics indicate
that after about 10 years, as many as half of the individuals no longer  have a pattern of be-
havior that meets full criteria for borderline personality disorder.
Risk and Prognostic Factors
Genetic and physiological. Borderline personality disorder is about five times more
common among first-degree biological relatives of those with the disorder than in the gen-
eral population. There is  also an increased familial risk for substance use disorders, anti-
social personality disorder, and depressive or bipolar disorders.
Culture-Related Diagnostic Issues
The pattern of behavior seen in  borderline personality disorder  has been identified in many
settings around the world. Adolescents and youn g adults with identity  problems (especially
when accompanied by substance use) may transiently display behaviors that misleadingly