From a paper by John Cacioppo, PhD:
Social isolation is typically defined in the epidemiological
literature in terms of a few simple indexes
such as marital status, contact with a close friend,
religious member, and member of voluntary groups.
The literature on the hypothesized human need to
belong, in contrast, has emphasized the psychological
impact of social interactions and relationships rather
than their presence or absence (eg, 5). Although a
measure of marital status, contact with family and
friends, church membership, and/or membership in
voluntary groups may correlate with feelings of social
isolation, the correlation is imperfect for several reasons.
Time spent alone can foster restoration or constructive
efforts rather than feelings of isolation, for
instance, and conflicts with marital partners and
friends can create feelings of loneliness as well as
elevations in autonomic function and stress hormones
over extended periods (6). Even church membership,
an index of social integration, can produce feelings of
conflict and isolation (7).
(Think about this before you head to midnight mass. )