A system for providing a treatment session for behavior therapy of a subject, the system comprising a computing system, a head mounted display configured to reproduce a video signal received from the computing system; one or more sensors configured to measure an orientation of the head mounted display of the subject, and one or more physiological sensors for measuring a physiological state of the subject, the computing system comprising a memory and a processor, wherein the memory stores computer program instructions executable by the processor, said instructions comprising functionality to execute a method of providing a behavior therapy, the method comprising: continuously receiving from the one or more sensors an orientation of the head mounted display of the subject; continuously receiving from the one or more physiological sensors a measured parameter indicative of the physiological state of the subject; continuously determining a video signal including an avatar representing the subject in a virtual reality scenario to be displayed on the head mounted display taking into account the orientation of the head mounted display, wherein the video signal includes an indication of a physiological state of the avatar; and the virtual reality scenario including a stressful episode for the subject, sending the video signal to the head mounted display for visualization, wherein during a first period of the session the indication of the physiological state of the avatar corresponds to the measured physiological state of the subject, during a second period of the session the indication of the physiological state of the avatar does not correspond to the measured physiological state of the subject, and further comprising a transitory period between the first period and the second period, wherein the indication of the physiological state of the subject is gradually manipulated, and wherein the second period includes the stressful episode. a head mounted display configured to reproduce a video signal received from the computing system; one or more sensors configured to measure an orientation of the head mounted display of the subject, and one or more physiological sensors for measuring a physiological state of the subject, the computing system comprising a memory and a processor, wherein the memory stores computer program instructions executable by the processor, said instructions comprising functionality to execute a method of providing a behavior therapy, the method comprising: continuously receiving from the one or more sensors an orientation of the head mounted display of the subject; continuously receiving from the one or more physiological sensors a measured parameter indicative of the physiological state of the subject; continuously determining a video signal including an avatar representing the subject in a virtual reality scenario to be displayed on the head mounted display taking into account the orientation of the head mounted display, wherein the video signal includes an indication of a physiological state of the avatar; and the virtual reality scenario including a stressful episode for the subject, sending the video signal to the head mounted display for visualization, wherein during a first period of the session the indication of the physiological state of the avatar corresponds to the measured physiological state of the subject, during a second period of the session the indication of the physiological state of the avatar does not correspond to the measured physiological state of the subject, and further comprising a transitory period between the first period and the second period, wherein the indication of the physiological state of the subject is gradually manipulated, and wherein the second period includes the stressful episode. continuously receiving from the one or more sensors an orientation of the head mounted display of the subject; continuously receiving from the one or more physiological sensors a measured parameter indicative of the physiological state of the subject; continuously determining a video signal including an avatar representing the subject in a virtual reality scenario to be displayed on the head mounted display taking into account the orientation of the head mounted display, wherein the video signal includes an indication of a physiological state of the avatar; and the virtual reality scenario including a stressful episode for the subject, sending the video signal to the head mounted display for visualization, wherein during a first period of the session the indication of the physiological state of the avatar corresponds to the measured physiological state of the subject, during a second period of the session the indication of the physiological state of the avatar does not correspond to the measured physiological state of the subject, and further comprising a transitory period between the first period and the second period, wherein the indication of the physiological state of the subject is gradually manipulated, and wherein the second period includes the stressful episode.