Spousal concordance for substance use and anxiety disorders

Assortative mating -- the tendency for mate selection to occur on the basis of similar traits -- plays an essential role in understanding the genetic contribution to psychiatric illness. It also carries significant impact on clinical prognosis and is an important mechanism explaining spousal concordance. This study uses a family study design ascertaining 225 probands with substance abuse/dependence, anxiety disorders, and controls to address: (1) Is there spousal concordance or cross-concordance for substance use and/or anxiety disorders? (2) Is the spousal concordance or cross-concordance associated with worse clinical outcomes? (3) What is the mechanism of the concordance or cross-concordance? Results show a high magnitude of spousal concordance for substance use disorders with a third of the substance probands' spouses also substance dependent. In contrast, there was no spousal concordance for anxiety disorders. Couples were also concordant for having "no disorders." Both substance use and anxiety disorder concordance were associated with poorer global functioning and persistent illness. Assortative mating is a likely mechanism for spousal concordance given the elevated rate of substance use disorders among the relatives of spouses' of substance probands. Implications for family/genetic studies and the transmission of substance use disorders and "no disorders" include: (1) at the individual level, spousal concordance influences probands' course of illness, couples' marital functioning, and offspring's genetic and environmental context; and (2) at the population level, it shifts the general distribution of substance use disorders and "no disorders" by reducing the "average" couple concordance and increasing the number concordant and discordant couples at extremes of the distribution.