In summary the invention utilizes a patient's interaction with a user interface 120 of a controllable lighting system 100. The user interface enables light characteristics of the lighting system 100 to be adjusted such as the light color emitted from a light source 110 of the lighting system 100. A monitor 130 is provided for monitoring how the patient interacts with the user interface 120, e.g. by monitoring how frequent the patient interacts with the user interface, the monitored number of interactions may be processed by a processor 140 to determine a value of the coping style which indicates how active or passive the patient is.