Background: Geographical variation in the prevalence of common mental disorders has not been explained adequately.
Aims: To investigate whether regional mental health differences in Wales would persist after having taken into account the characteristics of individuals and regional social deprivation.
Method: Data from the 1998 Welsh Health Survey were used. Common mental disorders were assessed with the mental health index included in the Short-Form 36 health survey (SF-36). The data were analysed using a multi-level linear regression model.
Results: Of the total variance in the mental health index, 1.47% occurred at regional level (95% CI 0.56-2.38). Adjustment for individual characteristics did not explain the between-region variation. A higher area deprivation score was associated with a higher score on the mental health index.
Conclusions: Mental health differences in Wales are partly explained by the level of regional social deprivation.