Chronically high cortisol levels can be harmful to an individual by:

High levels of cortisol can affect sleep; even if you sleep well, you will still feel fatigued. Another problem is weight gain, especially in the abdominal area. This problem alone can raise blood pressure levels, but high levels of cortisol with only cause your pressure to go higher, leading to a higher risk of heart attack and stroke. Anxiety and depression can also occur due to high levels of cortisol.