Understanding fundamental nanoassembly processes on intermediate scales between molecular and continuum scales requires an in-depth analysis of the coupling between particle interactions and molecular details. This is because the discrete nature of the solvent becomes comparable to the characteristic length scales of assembly. Utilizing the spatial density response of a solvent to a surface in conjunction with the Clausius-Mossotti equation, we present a simple theory relating the discrete nature of solvent to dispersion interactions. Our study reveals that dispersion interactions are indeed sensitive to the spatial variation of solvent density, manifesting in dramatic deviations in van der Waals forces from the conventional formulation (e.g., with uniform solvent density). This study provides the first steps toward relating molecular scale principles, namely the detailed nature of solvent response to an interface, to the underlying hydration forces between surfaces.