Measures	Description	For which populations
Subjective social isolation	The University of California at Los Angeles (UCLA) Loneliness Scale [115]	A unidimensional scale to assess the frequency and intensity of one’s lonely experiences, 20 items	General population (e.g. elderly, lonely students, immigrants) People with mental health problems (e.g. psychiatric inpatients, people with depression)
	UCLS-8 [6]	A short-form of UCLA Loneliness Scale, 8 items	General population (e.g. university students, adolescents, elderly sample) People with mental health problems (e.g. people with depression, mixed sample with various diagnoses)
	The De Jong-Gierveld Loneliness Scale [116]	A 11-item scale measures the feeling of severe loneliness, contains 5 positive and 6 negative items A short-form contains 6 items of the original De Jong-Gierveld Loneliness Scale (3 items for emotional loneliness and 3 items for social loneliness)	General population (e.g. national survey samples from several countries, elderly Chinese) People with mental health problems (e.g. mixed samples with various diagnoses)
	Multidimensional Scale of Perceived Social Support (MSPSS) [57]	A 12-item scale to measure perceived overall amount of social support and support from significant other/friends/family	General population (e.g. Chinese university students, young adults, adults with physical disabilities) People with mental health problems (e.g. people with post-traumatic stress disorder, women with severe depressive symptoms)
Objective social isolation	Social Network Index (SNI) [92]	A 12-item scale, measures the number of people one has regular contact with	General population (e.g. women with breast cancer, people with severe traumatic brain injury, African-Americans in urban area) People with mental health problems (e.g. old adults with depressive symptoms, people with post-traumatic stress disorder)
	The Pattison Psychosocial Kinship Inventory (PPKI) [117]	Measures the number of people and relationships one considers as important	General population (e.g. dysfunctional families) People with mental health problems (e.g. adults with schizophrenia, people with psychosis)
Measures focus on both domains	Lubben Social Network Scale (LSNS-6)	A revised version, contains 6 items, evaluates the quantity and quality of one’s relationship with family and friends	General population (e.g. community-dwelling elderly, Korean American caregivers) People with mental health problems (e.g. mixed samples with different diagnoses, depressed immigrants)
	Social Network Schedule (SNS) [78]	A 6-item scale, measures both quantitative (i.e. the size of one’s social network, the frequency of social communication and the time one spent on socialisation) and qualitative (i.e. quality and intimacy of one’s social relationships, the intensity of social interactions) aspects of one’s social connections	People with mental health problems (e.g. people with non-organic psychosis, people with intellectual disability)
	Medical Outcomes Study (MOS) Social Support Scale [64]	A 19-item survey measures dimensions of social support: emotional/informational, tangible, affectionate and positive social interactions	General population (people with heart failure in Hong Kong, mothers with children in treatment) People with mental health problems (e.g. adults with schizophrenia spectrum or affective disorder)
	Interview Schedule for Social interaction (ISSI) [61]	50 items, measures the availability and perceived adequacy of attachment and social integration	General population (e.g. patients with rheumatoid arthritis, people from Canberra suburbs) People with mental health problems (e.g. outpatients with schizophrenia, inpatient male offenders)