High levels of stress can also cause an episode or make symptoms worse for someone who already has mental illness. For bipolar disorder, stress can contribute to hypomania and mania. For schizophrenia, it may contribute to hallucinations and delusions. And for MDD, it can deepen depression. 
This is why managing stress is so important. In order to manage stress, we need to know the warning signs that stress levels are too high and learn healthy coping techniques. 

Learn more at https://www.nami.org/Blogs/NAMI-Blog/January-2020/Ways-to-Manage-and-Cope-with-Stress