Loneliness is a global public health concern. Investigating loneliness in the general population offers a greater generalizability across various levels of health-related impairments, the identification of at-risk individuals, the detection of different loneliness severity levels, and broader insights into social determinants. Previous studies have shown that loneliness might be a transient or chronic experience, depending on how consistently it is reported across at least two timepoints. This study aimed to assess differential associations of chronic and transient with various domains of psychopathology.

Participants were enrolled from the general population and assessed at two timepoints spanning 6–7 months. Depressive symptoms, generalized anxiety, social anxiety, and paranoid thoughts were measured using self-reports. The data were analyzed using binary logistic regressions.

Altogether, 3,275 participants completed both assessments with a retention rate of 64.2%. Chronic loneliness was associated with higher baseline and follow-up scores across all symptom domains. The strongest association was observed for social anxiety. Transient loneliness was not robustly associated with symptom scores. It was not significantly associated with depressive symptoms (at either of timepoints) and paranoid ideation (at baseline). The strongest association was observed for generalized anxiety. Chronic loneliness, compared to transient loneliness, was associated with significantly higher odds of social anxiety, depressive symptoms, and paranoid ideation, but not generalized anxiety.

Both transient and chronic loneliness are associated with mental health outcomes, with the latter one showing generally stronger associations. Risk stratification and early intervention among individuals experiencing loneliness might be needed to prevent the development of more severe psychopathology.

Perceived loneliness and objective social network size are related but distinct factors, which negatively affect mental health and are prevalent in patients who have experienced childhood maltreatment (CM), for example, patients with persistent depressive disorder (PDD) and borderline personality disorder (BPD). This cross-diagnostic study investigated whether loneliness, social network size, or both are associated with self-reported CM.

Loneliness and social network size were assessed in a population-based sample at two time points (Study 1, N = 509), and a clinical group of patients with PDD or BPD (Study 2, N = 190) using the UCLA Loneliness Scale and the Social Network Index. Further measures were the Childhood Trauma Questionnaire, and standard depression rating scales. Linear regression analyses were applied to compare associations of loneliness or social network size with CM. Multiple mediation analyses were used to test the relative importance of loneliness and social network size in the relationship between CM and depressive symptoms.

In both studies, loneliness showed a stronger association than social network size with CM. This was particularly marked for emotional neglect and emotional abuse. Loneliness but not social network size mediated the relationship between CM and depressive symptoms.

Loneliness is particularly associated with self-reported CM, and in this respect distinct from the social network size. Our results underline the importance of differentiating both psychosocial constructs and suggest focusing on perceived loneliness and its etiological underpinnings by mechanism-based psychosocial interventions.