The compartmental structure for the continuous-time Markov model describing the temporal courses of probabilities of adverse event (AE) intensities (0 = no AE, 1 = mild AE, 2 = moderate AE, 3 = severe AE). Forward “worsening” rate constants are represented by K0,1, K1,2, and K2,3, while the backward “recovery” rate constants are represented by K1,0, K2,1, and K3,2