Personality disorders (PDs) are associated with interpersonal dysfunction, loneliness, and reduced social embeddedness. This study investigates loneliness and social network size in association with self- and clinician-rated personality functioning regarding the DSM-5's Alternative Model for Personality Disorders (AMPD). Eighty psychiatric inpatients including participants with and without PDs completed the Semi-structured Interview for Personality Functioning, the Level of Personality Functioning Scale - Brief Form, the UCLA Loneliness Scale, and the Social Network Index. Patients with PDs reported more loneliness and personality dysfunctioning than patients without PDs. Social network size did not differ between patient groups and showed lower correlations with personality functioning compared to loneliness. Loneliness was further associated with deficits in personality functioning. Deficits in distinct AMPD domains and loneliness may constitute transdiagnostically relevant factors that are related and mutually reinforcing. This could be important for identifying patients beyond PD diagnoses who are at risk of poor psychosocial functioning and require tailored psychotherapy.
Keywords: Alternative Model for Personality Disorders; loneliness; personality disorders; personality functioning; social network size.