The prevalence of personality disorders in psychiatric outpatients with borderline intellectual functioning: Comparison with outpatients from regular mental health care and outpatients with mild intellectual disabilities.

BACKGROUND There is little research on the subject of personality disorder (PD) in individuals with borderline intellectual functioning (BIF). Unlike in most countries, in the Netherlands, patients with BIF are eligible for specialized mental health care. This offers the unique possibility of examining the rates of PDs in patients, who in other countries are treated relatively invisibly in regular mental health care. AIM To compare, in a naturalistic setting, the frequency of PD diagnoses in outpatients with BIF with outpatients from regular mental health care and outpatients with mild ID. METHODS We compared the rates of all DSM-IV-TR axis II PDs in outpatients with BIF (BIF group; n = 235) with rates of the same disorders in outpatients from regular mental health care (RMHC group; n = 1026) and outpatients with mild intellectual disability (ID) (mild ID group; n = 152) in a naturalistic cross-sectional anonymized medical chart review. RESULTS Over half of the patients with BIF (52.8%) were diagnosed with a PD, compared with one in five in the RMHC group (19.3%) and one in three of the mild ID group (33.6%). All PD diagnoses, except for cluster A PDs and histrionic PDs, were most frequently diagnosed in the BIF group. PD NOS and borderline PD were the most frequently diagnosed PDs in BIF. The majority of PD patients had one or more comorbid axis I disorder. CONCLUSION There is a high frequency of PD diagnoses in BIF outpatients in daily clinical practice. In anticipation of further scientific research, results suggest that PDs should not be overlooked in patients with BIF.