Medically unexplained and explained physical symptoms in the general population: Association with prevalent and incident mental disorders

Background
Clinical studies have shown that Medically Unexplained Symptoms (MUS) are related to common mental disorders. It is unknown how often common mental disorders occur in subjects who have explained physical symptoms (PHY), MUS or both, in the general population, what the incidence rates are, and whether there is a difference between PHY and MUS in this respect.
Aim
To study the prevalence and incidence rates of mood, anxiety and substance use disorders in groups with PHY, MUS and combined MUS and PHY compared to a no-symptoms reference group in the general population.
Method
Data were derived from the Netherlands Mental Health Survey and Incidence Study-2 (NEMESIS-2), a nationally representative face-to-face survey of the general population aged 18-64 years. We selected subjects with explained physical symptoms only (n=1952), with MUS only (n=177), with both MUS and PHY (n=209), and a reference group with no physical symptoms (n=4168). The assessment of common mental disorders was through the Composite International Diagnostic Interview 3.0. Multivariate logistic regression analyses were used to examine the association between group membership and the prevalence and first-incidence rates of comorbid mental disorders, adjusted for socio-demographic characteristics.
Results
MUS were associated with the highest prevalence rates of mood and anxiety disorders, and combined MUS and PHY with the highest prevalence rates of substance disorder. Combined MUS and PHY were associated with a higher incidence rate of mood disorder only (OR 2.9 (95%CI:1.27,6.74)).
Conclusion
In the general population, PHY, MUS and the combination of both are related to mood and anxiety disorder, but odds are highest for combined MUS and PHY in relation to substance use disorder. Combined MUS and PHY are related to a greater incidence of mood disorder. These findings warrant further research into possibilities to improve recognition and early intervention in subjects with combined MUS and PHY.