Estimated kinetic parameters of normal, PTSD, and depressed subjects used in the bifurcation analysis and numerical integration.

Lb and Ub are the lower and upper bounds respectively used after multiple iterations. The Hills coefficient “n” is taken as 4 because the 2 molecules of cortisol binds to the dimer to form a complex that is involved in the negative feedback regulation. k is the estimated bifurcation parameter used in the simulation of the full ordinary differential equation (ODE) model. To simulate the bifurcation diagram, the estimated k for normal, PTSD and depressed subjects was adjusted to reach the stable steady state, after which the parameter was slowly increased to sweep the region for bistablity and Hopf bifurcation. All the other parameters employed for bifurcation analysis were kept constant. The degradation rates K are extremely high to be directly used in the simulations. Therefore, we have chosen a much smaller lower and upper bound values for all the degradation values by scaling down all values in hours approximately by a factor of 100–1000.