Is it possible for anyone under 18 to be diagnosed with borderline personality disorder?

Yes: For many reasons, diagnosing personality disorders in teens is dicier. For example, teens may "try out" different personality styles that can look like a personality disorder but don't last. Even so, the diagnostic rules (dsm-iv) specify that most personality disorders, including bp, can be diagnosed under age 18. The only added requirement is that symptoms must be present for at least a year.

Yes,: But we try not to diagnose children or adolescents with any personality disorder unless the symptoms are pervasive, persistent and unlikely to be limited to a particular developmental stage or axis i illness.