The 2014 IOM report "Capturing Social and Behavioral Domains and Measures in Electronic Health Records" described three subdomains of social relationships that affect patient health and well-being. However, most social risk screeners currently assess only one subdomain, frequency of social connections. We are proposing a three-item Brief Social Connectedness (SC) screener that additionally assesses risks in social/emotional support and loneliness/social isolation subdomains. For this cross-sectional study, we used data from a 2021 Kaiser Permanente Northern California (KPNC) social risk survey for 2244 members ages 35-85 years. The survey included three validated questions that covered the SC subdomains (frequencies of social contacts with people they care about, feeling lonely/socially isolated, and getting enough social/emotional support). Variables representing moderate/high versus low risk were created for each subdomain. We used weighted data for bivariate analyses and modified log-Poisson regression models that adjusted for age, sex, race, and ethnicity to examine cross-sectional associations among the three subdomain risks, as well as with two structural SC risks, living alone and not being in a committed relationship. We then used modified log-Poisson regression models to study cross-sectional associations of these five SC variables with three single-item self-report measures of emotional health. In regression models that included all five SC variables, loneliness/social isolation and social/emotional support risks were significantly associated with all three emotional health measures, while frequency of social contacts, living alone, and no committed relationship were not. However, low frequency of social contacts and no committed relationship significantly increased risk of often feeling lonely/socially isolated and lacking in social/emotional support. A three-item social connectedness screener that assessed risks of loneliness/social isolation, inadequate social/emotional support, and low frequency of social contacts provided more comprehensive information about emotional health risks than social connection frequency alone.