  Quantum regression theorem is a very useful result in open quantum system and
extensively used for computing multi-point correlation functions. Traditionally
it is derived for two-time correlators in the Markovian limit employing the
Schr\"odinger picture. In this paper we make use of the Heisenberg picture to
derive quantum regression theorems for multi-time correlation functions which
in the special limit reduce to the well known two-time regression theorem. For
multi-time correlation function we find that the regression theorem takes the
same form as it takes for two-time correlation function with a mild restriction
that one of the times should be greater than all the other time variables.
Interestingly, the Heisenberg picture also allows us to derive analogue of
regression theorem for out-of-time-ordered correlators (OTOCs). We further
extend our study for the case of non-Markovian dynamics and report the
modifications to the standard quantum regression theorem. We illustrate all of
the above results using the paradigmatic dissipative spin-boson model.
