Social Network Index (SNI)

Abstract

The Social Network Index (SNI) is a widely used psychological instrument designed to quantify an individual’s level of social integration and structural social ties. The scale assesses participation in 12 distinct types of social relationships, ranging from intimate family connections (spouse, parents, children) to broader community affiliations (friends, neighbors, workmates, religious and non-religious groups, and volunteers). The primary scoring method assigns one point for each relationship type (up to a maximum of 12) in which the respondent engages in contact (in person or by phone) at least once every two weeks. The SNI yields measures of network diversity, total network size, and the number of embedded networks, making it a powerful tool for research in health psychology and epidemiology.

Keywords

Social Network Index, SNI, Social support, Network diversity, Social ties, Social integration, Psychoneuroimmunology, Social relationships, Structural support, Cohen scale

Authors

Cohen, S.

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Purpose

The primary purpose of the Social Network Index (SNI) is to provide a quantitative assessment of the structural aspects of an individual’s social environment. It systematically measures the extent of social roles and contact frequency across a comprehensive range of interpersonal domains.

The instrument is specifically designed to assess participation in 12 defined categories of social relationships. By calculating the diversity of these roles (network diversity) and the sheer number of high-contact individuals (network size), the SNI serves as a crucial predictor variable in studies examining the relationship between social environment and physical or mental health outcomes, such as susceptibility to illness or chronic stress response.

Construct

The SNI primarily measures the construct of Social Integration, which refers to the objective presence and frequency of social ties within an individual’s life. Unlike measures of perceived support quality, the SNI focuses on the measurable structure of the network.

The scale operationalizes social integration through three core measures: the Number of High-Contact Roles (Network Diversity, max score 12), the Number of People in the Social Network (total size of high-contact individuals), and the Number of Embedded Networks (reflecting concentrated activity in specific domains like family or work). High scores on the SNI are hypothesized to indicate robust social capital, which is frequently associated with positive physiological and psychological resilience.

Validity

The validity of the SNI is strongly supported by its consistent use in epidemiological and psychoneuroimmunology research, demonstrating significant predictive validity. The original validation work by Cohen and colleagues (1997) established a robust link between lower scores on the SNI (indicating poorer network diversity) and increased susceptibility to infectious disease, such as the common cold, even after controlling for demographic and behavioral factors.

Further studies have confirmed its concurrent validity, showing that SNI scores correlate appropriately with other established measures of social support and social engagement. Moreover, the SNI’s structural quantification of social networks has been linked to biological markers, including amygdala volume and cortical functional connectivity, reinforcing its utility as a valid measure of objective social environment influencing health.

Reliability

While specific Cronbach’s alpha coefficients are less relevant for an index measure composed of distinct social roles, the reliability of the SNI typically relies on its stability and consistency across time (test-retest reliability). Because the SNI measures structural components—the presence or absence of major life roles (e.g., spouse, employee, church member)—these components are generally stable for adult populations over short to medium time periods, contributing to the stability of the Network Diversity score.

In research settings, the clear definition of the 12 social roles and the binary scoring criterion (contact frequency of at least once every two weeks) ensures high inter-rater reliability and objective scoring consistency.

Factor Analysis

The SNI is designed as a composite index rather than a scale based on latent factors derived from factor analysis. The primary score, Network Diversity, is an additive count of 12 distinct, non-overlapping social roles.

However, the expanded scoring method acknowledges inherent domains within the network structure, such as family, friends, and work. The calculation of Number of Embedded Networks (max 8 domains) implicitly relies on grouping related items, suggesting that while the index is not factor-driven, the distinct categories represent separable facets of an individual’s social life. Researchers often analyze these sub-domains independently to understand which specific types of social ties are most influential in a given outcome.

Instrument

Test Type: Self-report psychometrics questionnaire, Index measure

Format: Structured items requiring frequency counts and categorical answers, yielding three main scores: Network Diversity, Network Size, and Embedded Networks.

Language Available: Primarily English; translations may exist in specific research contexts.

Population Group: General adult population (individuals engaged in various life roles such as employment, marriage, and community groups).

Age Group: Typically utilized with adults (18+).

Population Details: Suitable for use across various demographic groups, provided they are capable of self-reporting frequency of social ties and role participation.

Test Methodology: Respondents indicate their marital status, the existence of specific relationships (e.g., parents, children, workmates), and the number of people within those roles with whom they have contact (in person or by phone) at least once every two weeks.

Keywords

Social health, Social capital, Network size, Psychological assessment, Health psychology, Structural support, Social diversity, Epidemiology

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Authors

Author ORCID Identifier: Not publicly available/Applicable for S. Cohen based on this data.

Affiliation Email addresses: Unavailable.

Correspondence Address: Unavailable (Author S. Cohen associated with Carnegie Mellon University, Department of Psychology).

Permissions & Fee and Test Year

The Social Network Index was developed by Sheldon Cohen. The primary validation and publication year is 1997. The scale is widely used in academic research and is generally considered available for non-commercial research purposes, though researchers should check current guidelines set by Dr. Cohen or his affiliated institution (Carnegie Mellon University) for formal permissions. The psychometric basis is detailed in the reference: Cohen, S., Doyle, W. J., Skoner, D. P., Rabin, B. S., and Gwaltney, J. M., Jr. (1997). Social ties and susceptibility to the common cold. Journal of the American Medical Association, 277, 1940-1944.

Reference’s

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

Bickart, K. C., et al (2011). Amygdala volume and social network size in humans. Nature Neuroscience, 14, 163-164.

Bickart, K. C., et al (2012). Intrinsic amygdala–cortical functional connectivity predicts social network size in humans. Journal of Neuroscience, 32, 14729-14741.

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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.

Social Network Index

Instructions: This questionnaire is concerned with how many people you see or talk to on a regular basis including family, friends, workmates, neighbors, etc. Please read and answer each question carefully. Answer follow-up questions where appropriate.

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 )

         (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               (2) father             (3) both         _ (4) not

only                         only                                               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                 (2) father                (3) both

only                            only

5. How many other relatives (other than your spouse, parents & 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. How 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 )

           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. How 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 )

           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

Scoring the Social Network Index

MEASURES

• Number of high-contact roles (network diversity)
• Number of people in social network
• Number of embedded networks

Number of High-Contact Roles (Network Diversity)

Definition: This is the number of social roles in which the respondent has regular contact (i.e., at least once every 2 weeks) with at least one person. The maximum number of high-contact roles is 12. They are: spouse, parent, child, child-in-law, close relative, close friend, church/temple member, student, employee, neighbor, volunteer, and group member. [It would also be possible to count each group a person belongs to (question 12) as a separate social role, however we have not done this in our previous work.]

Computation: For each of the 12 possible high-contact roles, assign a 0 if the respondent does not have the role and a 1 if he/she does. The total number of high-contact roles is computed by summing the 0s and 1s. The table below shows which scale items are used in the computation and how each is scored.

• Role Item # Scores 1 if response is … spouse 1 1
• parent 2a not 0 child 3a not 0
• child-in-law 4a not 0 close relative 5a not 0 close friend 6a not 0
• church/temple member 7a not 0 student 8a not 0
• employee 9a & 9b not 0 for both items neighbor 10 not 0
• volunteer 11a not 0
• group member 12 not 0 for # of group members talked to every 2 weeks

Number of People in Social Network

Definition: This is the total number of people with whom the respondent has regular contact (i.e., at least once every 2 weeks).

Computation: For each of the 12 possible roles, determine the number of people with whom the respondent has regular contact. The total number of people in the social network is computed by summing across the 12 roles. The table below shows which scale items are used in the computation and how each is scored.

• Role Item # Scoring
• spouse 1 scores 1 if respondent is married, otherwise scores 0 parent 2a use the number indicated
• child 3a 1,2=1; 3=2
• child-in-law 4a 1,2=1; 3=2

close relative 5a use the number indicated close friend 6a use the number indicated church/temple member 7a use the number indicated student 8a use the number indicated employee 9a & 9b sum of 9a & 9b neighbor 10 use the number indicated volunteer 11a use the number indicated group member 12 sum of number of group members talked to at least once every 2 weeks

Number of Embedded Networks

Definition: This measure is meant to reflect the number of different network domains in which a respondent is active. The maximum possible is 8. They are: family, friends, church/temple, school, work, neighbors, volunteering, and groups. To receive a point for a domain, a respondent must have at least 4 high-contact people within that domain. The 5 family roles are collapsed into one network for this measure. To receive a point for family, they are required to have at least 3 high-contact family roles as well as 4 high-contact people.

Computation: If the subject meets the criteria for an embedded network, assign a score of 1 for that network, otherwise assign a 0. The total number of embedded networks is computed by summing the 0s and 1s. The table below shows the criteria used for each embedded network.

Embedded Network Scores

• 1 if S has at least 4 high-contact… Questionnaire Item(s)
• family
• family members and at least 3 high-contact family roles
• 1, 2a, 3a, 4a, 5a friends friends 6a
• church/ temple church/temple members 7a school students/teachers 8a
• work work associates 9a and 9b neighbors neighbors 10 volunteering fellow volunteers 11a groups group members 12