Does cortisol cause stress or is it simply an indicator of stress?

Response to stress.: Cortisol is the chief hormone that helps the body respond to stress. The more stress, the more cortisol is made. That's why it's at a high level in the morning when you wake up since this is a stressful time of the day. If you are exposed to stress very often, it may stay at a high level longer as the body gets used to it and so more is needed for a response. So it can indicate chronic stress.