Childhood Sexual Abuse and Rates of Loneliness in Adulthood.

Importance: Childhood sexual abuse (CSA) is a severe early-life trauma with well-established psychiatric sequelae. Prior studies have been limited by nonrepresentative samples, broad adversity measures, and a lack of dose-response characterization or formal effect modification testing in contemporary US populations. Objectives: To examine the association between prior CSA and adult loneliness and whether this association varies by sex, race and ethnicity, and age group. Design, Setting, and Participants: This cross-sectional study used data on 53 444 adults from the 2023-2024 Behavioral Risk Factor Surveillance System, a nationally representative survey of US adults. CSA was ascertained through retrospective self-report. Exposure: Self-reported history of CSA (never, once, or more than once). Main Outcomes and Measures: The main outcome was ordinal loneliness frequency (never, rarely, sometimes, usually, or always) estimated via survey-weighted multinomial logistic regression, adjusted for age, sex, race and ethnicity, marital status, educational level, employment, language, general health status, and tobacco use. Effect modification by sex, race and ethnicity, and age was formally tested. Analyses incorporated complex survey weights and inverse probability weighting to reduce confounding by measured covariates. Results: The analytic sample comprised 53 444 US adults (mean [SD] age, 56.8 [17.7] years; 55.1% female). CSA was associated with a clear dose-response gradient. The probability of never feeling lonely decreased from 40.9% (95% CI, 40.1%-41.8%) among unexposed adults to 23.1% (95% CI, 20.0%-26.3%) after repeated exposure. The probability of always feeling lonely increased from 2.1% (95% CI, 1.8%-2.3%) to 5.3% (95% CI, 3.9%-6.6%)-a 2.5-fold increase (adjusted OR, 4.48; 95% CI, 3.05-5.91; P < .001). In a binary analysis, any CSA was associated with an absolute risk difference of 18.1 percentage points (95% CI, 15.5-20.7 percentage points; P < .001), number needed to harm of 6, and population attributable fraction of 7.5% (95% CI, 6.4%-8.5%), suggesting approximately 6.2 million US adult loneliness cases may be associated with CSA. The dose-response pattern was consistent across sex, racial and ethnic groups, and age groups. Conclusions and Relevance: In this cross-sectional study of 53 444 US adults, CSA was associated with higher adjusted probabilities of adult loneliness in a graded dose-response pattern. This finding underscores the importance of trauma-informed strategies to address long-term psychosocial vulnerability among adults who were exposed to CSA.