Social Network Index (SNI)

Abstract

The Social Network Index (SNI) is a widely used psychological scale designed to quantify an individual’s level of social support and the complexity of their social environment. Developed primarily by Sheldon Cohen and colleagues, the SNI assesses participation across 12 distinct types of social relationships, focusing specifically on the frequency of face-to-face or telephone contact (at least once every two weeks).

This instrument is crucial in health psychology research, particularly for examining the causal link between social integration and physiological outcomes, such as immune function and susceptibility to illness. The SNI provides a structural measure of social ties, often correlating the diversity and size of the network with resilience against stress and disease.

Keywords

Social Network Index, SNI, Sheldon Cohen, Social Support, Social Ties, Social Integration, Health Psychology, Psychoneuroimmunology, Psychological Assessment, Social Relationships.

Authors

Sheldon Cohen, William J. Doyle, David P. Skoner, Bruce S. Rabin, Jack M. Gwaltney, Jr.

Purpose

The primary purpose of the SNI is to provide a quantitative measure of an individual’s current social integration by assessing their involvement in various social roles and the frequency of interaction within those roles. Unlike scales that focus solely on perceived emotional support, the SNI emphasizes structural social support—the actual existence, size, and diversity of the social network.

The scale was instrumental in pioneering research demonstrating that individuals with more extensive and diverse social networks exhibit increased resistance to infectious diseases, such as the common cold, underscoring the vital role of social connection in public health and well-being. Researchers utilize the SNI to categorize respondents into groups based on network size, allowing for robust statistical comparisons in studies relating social structure to stress reactivity and health outcomes.

Construct

The SNI measures the psychological construct of Social Integration, defined as the degree to which an individual participates in a broad range of social relationships. This construct is operationalized through 12 specific domains covering family, friends, and community ties. The final score often represents the total number of social roles in which the individual has regular contact, or a total count of individuals communicated with regularly.

The 12 measured domains ensure comprehensive coverage of an individual’s social environment, encompassing roles related to marriage, parenthood, family connections, professional life, religious involvement, and community engagement. High scores indicate a large, highly integrated, and diverse social network, which is consistently linked to positive health behaviors and outcomes.

Validity

Although the original publications (Cohen, 1991; Cohen et al., 1997) focused heavily on predictive validity concerning health outcomes, the SNI demonstrates robust construct validity. It successfully differentiates between individuals based on expected levels of social engagement, aligning with demographic factors such as marital status and employment.

The SNI’s strength lies in its criterion validity, particularly its ability to predict objective health markers. For example, the seminal 1997 study demonstrated a clear dose-response relationship: lower SNI scores were directly associated with higher susceptibility to developing a clinical cold following exposure to rhinovirus, confirming that the scale measures a meaningful biological correlate of social structure.

Reliability

The SNI is generally considered reliable for measuring stable structural components of social life. While specific internal consistency (e.g., Cronbach’s alpha) is often not reported for the overall scale due to the inherent diversity of the 12 distinct relationship domains, test-retest reliability across short periods is typically high for the structural component (i.e., the number of existing roles).

Reliability is further supported by the consistency with which the scale predicts outcomes across diverse populations and settings, suggesting that the items reliably capture the intended measure of social network structure over time.

Factor Analysis

Given that the SNI is designed to measure the breadth and diversity of social roles (a composite score of 12 distinct, though related, domains), formal factor analysis often reveals a multi-dimensional structure rather than a single, unified factor. However, researchers typically use the instrument to calculate a single score reflecting the total number of roles maintained with regular contact (the role diversity index), or the total number of people in the network, depending on the specific research hypothesis.

Studies focused on scale refinement have sometimes suggested grouping the 12 domains into broader factors, such as “Family Ties,” “Friendship Ties,” and “Community/Organizational Ties,” but the original and most common scoring method remains focused on the count of active, regularly maintained social roles.

Instrument

Test Type: Self-report questionnaire / Structural Social Support Index

Format: 12 main questions, often with sub-questions (a, b) detailing frequency of contact. Multiple-choice and fill-in-the-blank numerical responses are used.

Language Available: Primarily English, though translated and validated versions exist in numerous languages for international research.

Population Group: General adult population.

Age Group: Typically 18 years and older.

Population Details: Used extensively in epidemiological studies, clinical psychology, and psychoneuroimmunology research, often applied to healthy or mildly symptomatic populations to study resilience and disease susceptibility.

Test Methodology: Respondents indicate their status (e.g., marital status, employment) and then quantify the number of people in 12 defined categories with whom they have contact (in person or by phone) at least once every two weeks. Scoring usually involves summing the number of social roles in which the respondent has at least one regular contact.

Keywords

Structural support, Social roles, Social ties, Stress and health, Immunological function, Pittsburgh Common Cold Study, Social diversity, Quantitative assessment.

Authors

Author ORCID Identifier: Not available in source content.

Affiliation Email addresses: Not provided in source content.

Correspondence Address: Correspondence generally directed to Sheldon Cohen, Department of Psychology, Carnegie Mellon University (CMU).

Permissions & Fee and Test Year

The SNI is generally considered an academic instrument widely available for research purposes, often without explicit fees, though formal permission should be sought from the primary authors or Carnegie Mellon University for commercial use or modification. The scale was formally introduced and validated in 1991, with significant application in the 1997 study published in JAMA.

The original PDF can be downloaded here: http://www.midss.org/sites/default/files/social_network_index.pdf.

Reference’s

Cohen, S. (1991). Social Network Index. Unpublished measure.

Cohen, S., Doyle, W. J., Skoner, D. P., Rabin, B. S., & Gwaltney, J. M., Jr. (1997). Social ties and susceptibility to the common cold. Journal of the American Medical Association, 277, 1940–1944.

Cohen, Doyle, Skoner, Rabin, & Gwaltney, (1997). Social Network Index. In: Simmons C. A., Lehmann P. (eds). Tools for strengths-based assessment and evaluation, New York, NY: Springer, pp. 343-346. (2013). Google Scholar.

Additional relevant instruments and documentation can be found at: http://www.psy.cmu.edu/unionscohen/SNI.html and the common cold study PDF: www.psy.cmu.edu/unionscohen/cohen_common-cold.pdf.

Items of the Social Network Index (SNI)

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

1. Which of the following best describes your marital status?

(1) currently married & living together‚ or living with someone in marital-like relationship

(2) never married & never lived with someone in a marital-like relationship

(3) separated

(4) divorced or formerly lived with someone in a marital-like relationship

(5) widowed

2. How many children do you have? (If you don’t have any children‚ check “0” and skip to question 3.)

____0 ____1 ____2 ____3 ____4 ____5 ____6 ____7 or more

2a. How many of your children do you see or talk to on the phone at least once every 2 weeks?

____0 ____1 ____2 ____3 ____4 ____5 ____6 ____7 or more

3. Are either of your parents living? (If neither is living‚ check “0” and skip to question 4.)

____(0) neither ____(1) mother only ____(2) father only ____(3) both

3a. Do you see or talk on the phone to either of your parents at least once every 2 weeks?

____(0) neither ____(1) mother only ____(2) father only ____(3) both

4. Are either of your in-laws (or partner’s parents) living? (If you have none‚ check the appropriate space and skip to question 5.)

____(0) neither ____(1) mother only ____(2) father only ____(3) both ____(4) not applicable

4a. Do you see or talk on the phone to either of your partner’s parents at least once every 2 weeks?

_____(0) neither _____(1) mother only _____(2) father only ____(3) both only

5. How many other relatives (other than your spouse‚ parents‚ and children) do you feel close to? (If “0‚” check that space and skip to question 6.)

____0 ____1 ____2 ____3 ____4 ____5 ____6 ____7 or more

5a. Ho w many of these relatives do you see or talk to on the phone at least once every 2 weeks?

____0 ____1 ____2 ____3 ____4 ____5 ____6 ____7 or more

6. How many close friends do you have? (meaning people that you feel at ease with‚ can talk to about private matters‚ and can call on for help)

____0 ____1 ____2 ____3 ____4 ____5 ____6 ____7 or more

6a. How many of these friends do you see or talk to at least once every 2 weeks?

____0 ____1 ____2 ____3 ____4 ____5 ____6 ____7 or more

7. Do you belong to a church‚ temple‚ or other religious group? (If not‚ check “no” and skip to question 8.) _____no _____yes

7a. How many members of your church or religious group do you talk to at least once every 2 weeks? (This includes at group meetings and services.)

____0 ____1 ____2 ____3 ____4 ____5 ____6 ____7 or more

8. Do you attend any classes (school‚ university‚ technical training‚ or adult education) on a regular basis? (If not‚ check “no” and skip to question 9.) _____no _____yes

8a. How many fellow students or teachers do you talk to at least once every 2 weeks? (This includes at class meetings.)

____0 ____1 ____2 ____3 ____4 ____5 ____6 ____7 or more

9. Are you currently employed either full or part-time? (If not‚ check “no” and skip to question 10.)

____ (0) no _____ (1) yes‚ self-employed _____ (2) yes‚ employed by others

9a. How many people do you supervise?

____0 ____1 ____2 ____3 ____4 ____5 ____6 ____7 or more

9b. Ho w many people at work (other than those you supervise) do you talk to at least once every 2 weeks?

____0 ____1 ____2 ____3 ____4 ____5 ____6 ____7 or more

10. How many of your neighbors do you visit or talk to at least once every 2 weeks?

_____0 ____1 ____2 ____3 ____4 ____5 ____6 ____7 or more

11. Are you currently involved in regular volunteer work? (If not‚ check “no” and skip to question 12.)

_____no _____yes

11a. How many people involved in this volunteer work do you talk to about volunteering-related issues at least once every 2 weeks?

____0 ____1 ____2 ____3 ____4 ____5 ____6 ____7 or more

12. Do you belong to any groups in which you talk to one or more members of the group about group-related issues at least once every 2 weeks? Examples include social clubs‚ recreational groups‚ trade un‎ions‚ commercial groups‚ professional organizations‚ groups concerned with children like the PTA or Boy Scouts‚ groups concerned with community service‚ etc. (If you don’t belong to any such groups‚ check “no” and skip the section below.)

_____no _____yes

Consider those groups in which you talk to a fellow group member at least once every 2 weeks. Please provide the following information for each such group: the name or type of group and the total number of members in that group that you talk to at least once every 2 weeks.

Total number of group members

Group that you talk to at least once every 2 weeks