¹The National Cheng Kung University, Institute of Behavioral Medicine, Tainan, Taiwan, ²The National Cheng Kung University, Department of Psychiatry, National Cheng Kung University Hospital, College of Medicine, Tainan, Taiwan, ³The National Cheng Kung University, Department of Psychiatry, Dou-Liou Branch College of Medicine and Hospital, Tainan, Taiwan, ⁴The National Cheng Kung University, Department of Occupational Therapy, College of Medicine, Tainan, Taiwan, ⁵The National Cheng Kung University, Department of Psychiatry, College of Medicine,, Tainan, Taiwan, ⁶The National Cheng Kung University, Department of Psychiatry, College of Medicine, Tainan, Taiwan

Background: Loneliness is a major determinant of mental health and has been increasingly recognized as a critical transdiagnostic factor contributing to illness burden, suicidality, and impaired psychosocial functioning in bipolar disorder (BD). Early adversity is strongly linked to mood dysregulation, social impairment, and psychotic symptoms, yet the psychosocial mechanisms that shape loneliness across BD subtypes remain poorly understood. In particular, individuals with BD with psychotic features (BD-P) exhibit more severe cognitive and interpersonal difficulties than those without psychotic features (BD-NP), raising the question of whether social support—typically protective—functions differently across subgroups.

Aims & Objectives: 

1. Compare childhood adversity, perceived and actual social support, and loneliness among BD-P, BD-NP, and healthy controls (HC).
2. Examine correlations among early adversity, multiple domains of social support, and loneliness.
3. Test whether social support mediates the association between early adversity and loneliness in BD-P, BD-NP, and HC.

Method: A cross-sectional sample of 242 adults (BD-P = 60; BD-NP = 96; HC = 86) was recruited from a tertiary psychiatric center. Diagnostic confirmation used the MINI interview, and clinical symptoms were assessed with the Hamilton Depression Rating Scale and Young Mania Rating Scale. Early adversity measured using the Childhood Trauma Questionnaire–Short Form; loneliness using the UCLA Loneliness Scale; and social support using the Measure of Social Function Scale. Group differences were examined via t-tests, ANOVA, and χ² tests. Pearson correlations explored associations among variables. Mediation analyses (PROCESS Model 4; 5,000 bootstraps) tested whether social support mediated the adversity–loneliness relationship within each subgroup. Statistical significance was set at p < .05.

Results: Significant group differences emerged across all outcomes. Both BD-P and BD-NP reported greater childhood adversity and higher loneliness than HC, with BD-NP showing the highest loneliness levels (mean = 50.03 ± 10.68). Social support was significantly lower in both BD subgroups compared with HC, particularly in emotional support domains. Emotional neglect was the trauma type most strongly linked to reduced social support and elevated loneliness across all groups.
Correlational analyses demonstrated robust negative associations between social support and loneliness (r = –.47 to –.58, all p < .01), and positive associations between childhood adversity and loneliness.
Mediation analyses showed that social support significantly mediated the relationship between early adversity and loneliness in HC and BD-NP (indirect β = .04–.20; 95% CI excluding zero). No mediation effects were observed in BD-P, indicating that the presence of psychotic features disrupts the protective role of social support.

Discussion & Conclusions: Findings indicate that psychotic features define a distinct psychosocial pathway in bipolar disorder, marked by persistent loneliness and reduced capacity to benefit from supportive relationships. In contrast, BD-NP and HC demonstrated expected stress-buffering patterns in which social support mitigated the effects of early adversity.

These results suggest that loneliness in psychotic-spectrum BD may stem from trauma-related mistrust, impaired social cognition, and disrupted attachment processes. Clinically, BD-NP may benefit from interventions that enhance perceived and actual support, whereas BD-P may require approaches targeting mistrust, interpersonal schemas, and social cognitive deficits. Prioritizing social connection as a modifiable health determinant may reduce long-term psychosocial burden in bipolar disorder.