Testing this hypothesis has required the development of instruments to measure the social support obtained by individuals from their personal networks. Both cross-sectional and, more rarely, prospective longitudinal studies have been conducted, with depressive symptoms as the dependent variable. An integrative analysis of these studies suggest that a buffering effect does exist. The significance of such a finding is considerably diminished if it is acknowledged that the measures of social support are obtained almost entirely by self-report. It is plausible that persons who lack supportive relationships may tend to have personality traits conferring vulnerability to common mental disorders.
Genetic factors contribute both to personality and to environmental exposures.
The data suggest that it is not the actual social environment that matters for mental health, but its internal representation in people s minds. This is a disturbing prospect for psychiatric epidemiology which has traditionally looked to the social environment as a major source of aetiological factors. Clinicians working with older persons are familiar with the pattern of somatic symptoms of psychological origin. But it is unknown if older persons are indeed more prone to somatization after allowing for the higher level of physical morbidity in that age-group. It is also unknown if there is an interaction effect between age and culture, whereby the elderly might differ in either direction from younger adults between cultures.