Loneliness and mood symptoms in Parkinson's disease: An item-level network analysis

Loneliness is a common and clinically relevant experience in Parkinson's disease (PD), but little is known about how specific loneliness experiences interrelate with anxiety and depression in this population.

To characterize associations among the eight ULS-8 items, depression, and anxiety in people living with PD.

Baseline ULS-8 data were obtained from 768 participants in the Modifiable Variables in Parkinsonism Study, an online observational cohort of individuals with clinician-diagnosed PD. A regularized partial correlation network based on Spearman correlations was estimated using EBICglasso. Community structure (Walktrap algorithm), node strength, bridge strength, and nodewise predictability were examined. Network accuracy and stability were evaluated with nonparametric bootstrapping and case-dropping procedures.

Most ULS-8 items formed a closely connected loneliness community, whereas depression, anxiety, and the reverse-scored outgoingness item formed a second community. The strongest edge was between depression and anxiety. Among loneliness items, having no one to turn to, lacking companionship, and feeling isolated were the most central. Bridge strength was highest for depression, having no one to turn to, outgoingness, and anxiety.

Loneliness in PD was related to, but not reducible to, depression and anxiety. Endorsement of having no one to turn to may warrant assessment of both perceived social disconnection and mood symptoms. The outgoingness item should be interpreted cautiously because it may reflect affective state or response style in addition to loneliness.