We study the anyon statistics of 2+1 dimensional gauge theories based on the Breit Hamiltonian formalism for two-fermion elastic scattering. A Breit potential, the non-relativistic limit of the scattering amplitude, is derived to lowest order of coupling constant for Maxwell, Chern-Simons, and Maxwell-Chern-Simons theories respectively. An anyon phase angle is then extracted from the spin-orbit interaction in the Breit potential, We also find that a nontrivial anyon phase is induced from higher-order radiative corrections in the pure Maxwell theory.