Effectiveness of a Psychological Intervention to Reduce Social Isolation and Promote Social Connectedness in Young Adults

Participants assigned to the active intervention arm receive an 8-week, face-to-face group social skills training program, which involves weekly 120-minute sessions supplemented by a web-based digital platform designed to promote between-session practice and skill generalization.

The Korean Version of the Interpersonal Competence Questionnaire (K-ICQ) is a 31-item self-report measure of interpersonal competence. Each item is rated on a 5-point Likert scale from 1 (poor) to 5 (extremely good). The total score sums all items and ranges from 31 to 155. Higher scores indicate greater interpersonal competence, which is a better outcome.

The Social Skills Knowledge Test is an investigator-developed knowledge test created to objectively measure acquisition of the social skills content taught in the intervention. It consists of 21 items (multiple-choice and true/false) covering seven domains that correspond to the session curriculum: relationship formation skills, conversation skills I, conversation skills II, assertion skills, conflict management skills, dating skills, and workplace skills, with 3 items per domain. Each item has an unambiguously correct answer and is scored 1 (correct) or 0 (incorrect). The total score is the sum of correct responses and ranges from 0 to 21. Higher scores indicate greater knowledge of social skills, which is a better outcome.

The Korea University Social Isolation Scale (KUSIS) is a 9-item self-report measure of social isolation risk. Respondents rate their state over the past month, excluding people they currently live with. Each item is rated on a 4-point scale from 0 (never) to 3 (very much). The total score sums all items and ranges from 0 to 27, with a cut-off of 9 or higher indicating risk of social isolation. Higher scores indicate greater social isolation, which is a worse outcome.

The Lubben Social Network Scale-6 (LSNS-6) is a 6-item self-report measure of social network size and engagement; three items concern family and relatives, and three concern friends and other acquaintances. Each item is rated on a 6-point scale from 0 (none) to 5 (nine or more people). The total score sums all items and ranges from 0 to 30. Higher scores indicate a larger and more engaged social network, which is a better outcome.

The short-form UCLA Loneliness Scale-8 (ULS-8) is an 8-item self-report measure of loneliness abbreviated from the 20-item UCLA Loneliness Scale. Each item is rated on a 4-point scale from 1 (never) to 4 (always); two positively worded items are reverse-scored. The total score is the sum of all items and ranges from 8 to 32. Higher scores indicate greater loneliness, which is a worse outcome.

The Patient Health Questionnaire-9 (PHQ-9) is a 9-item self-report measure of depressive symptoms over the preceding two weeks, based on the DSM-IV diagnostic criteria for major depressive disorder. Each item is rated on a 4-point scale from 0 (not at all) to 3 (nearly every day). The total score is the sum of all items and ranges from 0 to 27. Higher scores indicate more severe depressive symptoms, which is a worse outcome.

The Generalized Anxiety Disorder-7 (GAD-7) is a 7-item self-report measure of the core symptoms of generalized anxiety disorder over the preceding two weeks. Each item is rated on a 4-point scale from 0 (not at all) to 3 (nearly every day). The total score is the sum of all items and ranges from 0 to 21. Higher scores indicate more severe anxiety symptoms, which is a worse outcome.

The Korean version of the Social Interaction Anxiety Scale-Social Phobia Scale Short Form (K-SIAS-SPS-SF) is a single 14-item self-report measure of social anxiety. Its items were derived by exploratory factor analysis of the pooled 40-item set of the Social Interaction Anxiety Scale and the Social Phobia Scale, and the resulting instrument is administered and scored as one scale comprising three correlated factors: social interaction anxiety (5 items), fear of overt evaluation (6 items), and fear of attracting attention (3 items). Each item is rated on a 5-point scale from 0 (not at all characteristic of me) to 4 (extremely characteristic of me). A single total score is obtained by summing all 14 items and ranges from 0 to 56, with a total score of 22 or higher indicating probable social anxiety disorder. Higher scores indicate greater social anxiety, which is a worse outcome.

The Mental Health Continuum-Short Form (MHC-SF) is a 14-item self-report measure of positive mental health over the past month, comprising three subscales: emotional well-being (3 items), social well-being (5 items), and psychological well-being (6 items). Each item is rated on a 6-point frequency scale from 0 (never) to 5 (every day). The total score sums all items and ranges from 0 to 70. Higher scores indicate greater well-being, which is a better outcome.

The Multidimensional Scale of Perceived Social Support (MSPSS) is a 12-item self-report measure of perceived social support from three sources: significant other, family, and friends, with 4 items per source. Each item is rated on a 7-point Likert scale from 1 (very strongly disagree) to 7 (very strongly agree). The total score sums all items and ranges from 12 to 84. Higher scores indicate greater perceived social support, which is a better outcome.

The Broad Autism Phenotype Questionnaire Short Form (BAPQ-SF) is a 14-item self-report measure that assesses core features of the autism spectrum as a continuous dimension in the general population. Each item is rated on a 6-point frequency scale from 1 (very rarely) to 6 (very often), and positively worded items are reverse-scored so that higher values reflect more pronounced traits. The total score sums all items and ranges from 14 to 84. Higher scores indicate more pronounced broad autism phenotype traits, which is a worse outcome.