Geographical variation in rates of common mental disorders in Britain: a prospective cohort study

BACKGROUND: There is little geographical variation in the prevalence of the common mental disorders. However, there is little longitudinal research. AIMS: To estimate variance in rates of common mental disorders at individual, household and electoral ward levels prospectively. METHOD: A 12-month cohort study of 7659 adults aged 16-74 years in 4338 private households, in 626 electoral wards. Data were collected as part of the British Household Panel Survey. Common mental disorders were assessed using the 12-item General Health Questionnaire (GHQ). Ward-level socio-economic deprivation was measured using the Carstairs index. RESULTS: Less than 1% of total variance, in onset and maintenance of common mental disorders and change in GHQ score between waves, occurred at ward level. However, 12% of variance, which is a statistically significant difference, was found at household level (a much smaller geographical unit) and this difference remained after further analyses. CONCLUSIONS: Ward level socio-economic deprivation does not influence the onset and maintenance of common mental disorders in Britain but local factors at the household level do. Reasons for this remain unclear