A method and an apparatus for monitoring the autonomous nervous system of a sedated patient. The method comprises steps of providing a skin conductance signal measured at an area of the patient's skin through a measurement interval, calculating a characteristic of said skin conductance signal, establishing a first output signal indicating the state of pain or discomfort in the patient, and a second output signal indicating the state of awakening in the patient, based on said characteristic of said skin conductance signal. The calculating of the signal characteristic comprises calculating a value representative of a statistical dispersion, e.g., the standard deviation, of the values of the skin conductance signal through the measurement interval.