He has translated these results into theoretical impacts on, for instance, rate of decay of linkage disequilibrium, and practical application in personalised medicine.

For instance, using the Framingham data, he showed that population stratification leads not only to fewer heterozygotes than predicted from Hardy–Weinberg equilibrium but also to spouses sharing genotypes at all ancestrally informative markers, accounted for by ancestry-related assortative mating in the previous generation.

[8] In 1999, with colleagues he published a sib-pair study that failed to replicate a previously observed linkage [9] between male sexual orientation and Xq28 DNA markers.

[12] Risch also discussed ethical issues underlying studies of socially significant traits and the under-representation of minority scientists in human genetics in his 2015 ASHG Presidential Address,[13] which received a standing ovation.

[14] With his colleague Kathleen Merikangas, Risch is possibly best known for introducing the concept of genome-wide association studies for the discovery and characterization of genetic variants of modest effects underlying complex diseases.