People with schizophrenia (PwS) can experience a range of cognitive diffiuclties and functional impairments, which may impede their ability to live independently and function successfully in the real-world. Research in the general population suggests that social factors, such as loneliness, can increase risk for dementia and other cognitive decline. However, there has been a dearth of studies examining the impact of loneliness on cognitive and functional outcomes in PwS. This study 1) investigated the relationship between loneliness and functional capacity, and 2) explored loneliness’ impact on functional capacity beyond variance attributable to other relevant factors.

This cross-sectional study included 52 adults with schizophrenia or schizoaffective disorder (PwS) and 48 adults without serious mental illness (non-SMI). Participants completed assessments of loneliness (revised UCLA Loneliness Scale version 3; UCLA-LS), functional capacity (UCSD Performance-Based Skills Assessment-Brief; UPSA-B), and neuropsychological functioning (MATRICS Consensus Cognitive Battery). UCLA-LS and UPSA-B scores were compared between groups using independent samples t-test. The relationship between loneliness and functional capacity was examined in each group using Pearson rs. Backwards stepwise multivariable regression using AIC selection was also conducted to explore the independent effect of loneliness on functional capacity after accounting for relevant covariates (age, education, cognitive composite, quality of social functioning, and number living in one’s household). Covariates were selected for inclusion if they were 1) significantly associated with UPSA-B scores, and 2) significantly differed between the PwS and non-SMI groups (p<.05).

Compared to the non-SMI group, mean scores among PwS indicated worse loneliness (UCLA-LS=46.9 [SD=9.9] vs 35.6 [10.2]; t=5.78, p<.001), and worse functional capacity (UPSA-B=57.9 [27.5] vs 79.7 [24.3]; t=-6.94, p<.001). Notably, loneliness was only correlated with functional capacity in the PwS group (r=0.29, p=.037), but was unrelated in the non-SMI group (r=-0.07, p=.637). Backwards stepwise multiple regression analysis predicting UPSA-B scores provided a significant final model (F=30.7, df=[4,87], R²=0.58, p<.0001) that included group status [B=0.22, p=.039], loneliness [B=0.15, p=.059], years of education [B=0.23, p=.018], and cognitive performance [B=0.51, p<.001] as contributing variables. Quality of social functioning and number of people living in one’s household were removed from the final model. The interaction between group status and loneliness on functional capacity was also explored, but was not significant and removed from the final model.

As expected, PwS performed worse than people without SMI on cognitive and functional capacity measures. On average, PwS also reported feeling lonelier than the non-SMI group, despite living, on average, with more people. Loneliness was associated with worse functional capacity; however, its contribution was not as strong as other factors including schizophrenia or schizoaffective disorder diagnosis, poorer cognitive functioning, and lower education. The number of people in one’s household and one’s quality of social functioning did not impact performance on a test of functional capacity after other variables, including loneliness, were considered. These findings provide preliminary support regarding the impact of loneliness, above and beyond other social constructs, on functional outcomes. Further research is required to understand loneliness’ specific role in functional capacity, and vice versa, among PwS.