Loneliness despite social integration: subjective loneliness without social isolation as a risk factor for psychotic-like experiences

BACKGROUND: Psychotic-like experiences (PLEs) are associated with subjective loneliness, as well as social isolation. However, few studies have examined how different combinations of loneliness and social isolation relate to overall PLEs and specific psychotic symptom domains. The aim of this study was to examine the associations between combinations of loneliness and social isolation and PLEs in a population-based sample in Japan. METHODS: Data were derived from the 2025 wave of the Japan Society and New Tobacco Internet Survey (JASTIS), including 25,424 adults aged 15-84 years. PLEs were assessed using the Japanese version of the PRIME Screen-Revised (PS-R). Loneliness was measured using the University of California, Los Angeles Loneliness Scale version 3, Short Form 3-item (UCLA-LS3-SF3), and social isolation was assessed using the Lubben Social Network Scale (LSNS-6). Logistic regression analyses with inverse probability weighting were conducted to examine associations between four categories of loneliness/social isolation and overall PLEs as well as six psychotic symptom domains. RESULTS: The weighted prevalence of PLEs was 4.3%. Compared with participants with both loneliness and social isolation, those with neither loneliness nor social isolation showed lower odds of overall PLEs (OR = 0.51, 95% CI 0.42-0.63), as did those with social isolation without loneliness (OR = 0.62, 95% CI 0.51-0.74). In contrast, participants with loneliness without social isolation had higher odds of overall PLEs (OR = 1.46, 95% CI 1.24-1.71). Symptom-domain analyses indicated heterogeneous patterns across domains. CONCLUSIONS: These findings demonstrate that loneliness without social isolation is particularly associated with PLEs, highlighting the importance of subjective loneliness as a correlate of PLEs. This suggests that reliance on objective indicators of social isolation alone may overlook individuals at elevated risk, emphasizing the importance of attending to subjective loneliness in population-based mental health research.