Are personality disorders in bipolar patients more frequent in the US than Europe?

Bipolar patients in the United States (US) compared to those from the Netherlands and Germany (here abbrev. as "Europe") have more Axis I comorbidities and more poor prognosis factors such as early onset and psychosocial adversity in childhood. We wished to examine whether these differences also extended to Axis II personality disorders (PDs).

793 outpatients with bipolar disorder diagnosed by SCID gave informed consent for participating in a prospective longitudinal follow up study with clinician ratings at each visit. They completed detailed patient questionnaires and a 99 item personality disorder inventory (PDQ-4). US versus European differences in PDs were examined in univariate analyses and then logistic regressions, controlling for severity of depression, age, gender, and other poor prognosis factors.

In the univariate analysis, 7 PDs were more prevalent in the US than in Europe, including antisocial, avoidant, borderline, depressive, histrionic, obsessive compulsive, and schizoid PDs. In the multivariate analysis, the last 4 of these PDs remained independently greater in the US than Europe.

Although limited by use of self report and other potentially confounding factors, multiple PDs were more prevalent in the US than in Europe, but these preliminary findings need to be confirmed using other methodologies. Other poor prognosis factors are prevalent in the US, including early age of onset, more childhood adversity, anxiety and substance abuse comorbidity, and more episodes and rapid cycling. The interactions among these variables in relationship to the more adverse course of illness in the US than in Europe require further study.