  It is well-known that electric dipole moment (EDM) constraints provide the
most stringent bounds on axion-mediated macroscopic spin-dependent (SD) and
time reversal and parity violating (TVPV) forces. These bounds are several
orders of magnitude stronger than those arising from direct searches in
fifth-force experiments and combining astrophysical bounds on stellar energy
loss with Eotvos tests of the weak equivalence principle (WEP). This is a
consequence of the specific properties of the axion, invoked to solve the
Strong CP problem. However, the situation is quite different for generic light
scalars that are unrelated to the strong CP problem. In this case, bounds from
fifth-force experiments and astrophysical processes are far more stringent than
the EDM bounds, for the mass range explored in direct searches.
