The optical Freedericksz effect induced by depolarized laser light in a nematic liquid crystal is investigated both theoretically and experimentally. By "depolarized" is here intended light having a rapidly varying polarization whose density matrix is isotropic. The main features of the phenomenon are determined only by the average properties of the light. However, when the light polarization dynamics is about one order of magnitude faster than the response time of the liquid crystal, the system becomes very sensitive to the temporal correlations of light polarization, i.e., to the fourth-order time correlations of the optical field. This prediction is confirmed by the experimental results.