Sleep for me is essential. For everybody it is! The difference is that if I had bad sleep or no sleep for 3-4 days my mind ‘switches’ and believes it should work harder and faster instead of getting tired and letting me know its time to wind down. Racing thoughts get out of control and within a week of this, an episode is certain. Sleep hygiene is crucial for anyone with mental health issues and is a topic worth exploring entirely on its own.
During times of depression, I over slept quite a lot. Sometimes till 2 or 3 in the afternoon. This can present its own problems and in my case I used sleep and dreaming as an escape from my reality. I studied dreams so I wouldn't have to face the world. I wouldn’t advise oversleeping as it can prolong the effects of depression and anxiety. Many times I’ve heard that 8 hours a night is optimum. I’ve found that 6-8 hours works for me. Find what works for you. There will be times when our bodies and minds may need more rest, and stress and anxiety can be indicators of this. Factor rest into your schedule if you have too, and take a mental health day from time to time.