Table 1. Social network metrics of interest and their definition.

Metric	Definition
Vertices	Number of Facebook friends of an ego (i.e., network size); an ego-level metric
Edges	Number of friendships in the network, including friendships between an ego’s friends; a network-level metric
Density*	The portion of potential connections in a network that are actual connections (calculated as the existing friendships over all possible friendships); a network-level metric
Isolates	Number of individuals with no friends other than the ego; a network-level metric
Diameter*	Maximum degree of separation between any two individuals in the network; a network-level metric
Communities*	Number of groups, sorted to increase dense connections within the group and decrease sparse connections outside it (i.e., to maximize modularity); a network-level metric
Closeness*	Average of how closely associated members are to one another; a network-level metric
Betweenness*	An average of the relative importance of all individuals within their own network, normalized as 2*betweenness/(vertices-1)(vertices-2); a network-level metric
Transitivity*	The extent to which the relationship between two nodes in a network that are connected by an edge is transitive (calculated as the number of triads divided by all possible connections); a network-level metric
Clusters*	Number of subnetworks; a network-level metric
Modularity	The strength of division of a network into communities (calculated as the fraction of ties between community members in excess of the expected number of ties within communities if ties were random); a network-level metric

* calculated after removing ego and isolates