We explain how mixed Hodge modules can be used to understand unitary representations of real groups as was conjectured by the speaker with Wilfried Schmid a while back. Along the way we obtain vanishing results for mixed Hodge modules on flag manifolds and a version of Saito's Kodaira vanishing theorem for twisted mixed Hodge modules. The proofs will depend on deformation and wall crossing arguments as well as the explicit determination of the associated graded of certain mixed Hodge modules.