The distribution of psychiatric and somatic III health: associations with personality and socioeconomic status.

OBJECTIVE: Psychiatric and somatic disorders frequently co-occur in the same individuals. We examined whether this happens because these types of morbidity share risk factors or because they are risk factors for each other.
METHODS: Negative binomial regression was used to examine, in a random sample of Dutch adults (N = 7076), cross-sectional associations of sociodemographic and personality variables like income and neuroticism with the presence, over 1 year, of 30 somatic and 13 psychiatric disorders, with the latter diagnosed by structured interview. We examined to what extent the links of these variables with these two morbidity types were independent of each other.
RESULTS: This population experienced 5050 somatic and 2438 psychiatric disorders during the preceding year. Subjects reporting more somatic disorders had more psychiatric disorders. Neuroticism, followed closely by low educational attainment, was the strongest correlate of both morbidity types. After adjustment for all other covariates including somatic morbidity, the number of psychiatric diagnoses rose 1.84-fold (95% confidence interval = 1.74-1.94) per standard deviation increase in neuroticism. Likewise, adjusted for all other covariates including psychiatric diagnoses, 1.42 (95% confidence interval = 1.35-1.50) times more somatic disorders were reported per standard deviation increase in neuroticism.
CONCLUSIONS: Personal features like neuroticism and low educational attainment are linked with psychiatric and with somatic morbidity. These links are largely independent. Although this study was cross-sectional, the results suggest that these different types of morbidity may have overlapping etiologies. Key words: Comorbidity, multimorbidity coefficient, negative binomial regression, epidemiology, neuroticism, social class.