Emotionally unstable personality disorder (EUPD) and complex post-traumatic stress disorder (CPTSD) reflect complex and highly comorbid disorders that bear significant impacts on a person's functioning. Despite the significant treatment needs of people with EUPD and complex trauma histories, the differential effects of trauma symptomology on functioning remain unexplored in this population. Prioritizing the most impactful symptoms is critical for providing timely and efficient treatment, over a reduced intervention period.

The current study sought to explore the relative associations of CPTSD symptoms with functional impairment in a clinical inpatient EUPD population.

A convenience sample of 45 females with a primary diagnosis of EUPD, admitted to a specialist inpatient DBT service, completed the International Trauma Questionnaire, as a measure of CPTSD symptomology and associated functional impairment.

At a diagnostic level, with the exception of affective dysregulation, meeting any of the CPTSD symptom clusters was significantly associated with meeting the functional impairment criterion. At a dimensional level, the severity of all CPTSD symptoms were significantly positively associated with the severity of functional impairments. However, only sense of threat and disturbances in relationships were significant predictors of functional impairment severity when controlling for other symptom clusters.

Trauma symptoms bear differential impacts on a person's ability to function in important domains of their lives. A persistent sense of threat and interpersonal difficulties stemming from traumatic experiences may reflect particularly crucial targets in interventions for individuals with EUPD and complex trauma needs. Implications for both research and clinical practice are discussed.