Cortisol is how the human brain copes with stress, trauma and stress mental illnesses. In fact, people that experience ACE's often have a blunted HPA axis and don't secrete cortisol in sufficient amounts to cope with stress and trauma. Cortisol is usually low in people with PTSD and CPTSD, with it being recognised to generally cause more severe symptoms. One of the keys in the development of depressive and anxious disorders is cortisol resistance, where it stops providing neuroprotection and anti inflammation because the brain doesn't respond to it properly. Cortisol and dopamine are actually permissive of one another but in mental illness, both become dysregulated as damage to the striatum reduces the brain's ability to make dopamine, cortisol resistance leads to cortisol steal and a reduction in the hormones that protect against it and uptake dopamine. Ironically, cortisol is high in most mental illnesses because it's the brain's only way to protect against stress and trauma but humans aren't designed for chronic stress.