Sleep seems like the ultimate passive activity, and the least productive part of our day (or night). But just the opposite is true. Sleep is a remarkably productive and critical part of our lives. Sleep helps both the brain and the body rejuvenate. Sleep has been shown to help keep the body’s immune system strong, and can also help regulate moods and reduce stress.

Because sleep is particularly important to brain health, establishing and maintaining good habits for restful, effective sleep – sometimes called good sleep hygiene – is a key component in managing the symptoms of depression or bipolar illness. How much sleep is enough sleep? How much is too much?

Everyone has trouble sleeping sometimes, and in general, most of us probably need more and better sleep than we’re getting. Yet good quality sleep can be the first thing to be compromised when we’re overscheduled, overstressed, or suffering from depression.

Different people need different amounts of sleep to function effectively during the day. There are three things to keep in mind when thinking about your own sleep quality:

Sleep is a process. The mind and body progress through several distinct stages during sleep. At each phase, different physiological processes take place, including changes in heart rate, brain activity, energy expenditure, muscle contraction and more. The process builds and cycles through the night. Although all of this activity takes place without your knowledge or control, your role is nonetheless key. You set the stage for effective sleep by making sleep a priority, giving yourself permission to sleep instead of sacrificing sleep for other activities, and setting aside a sufficient amount of time for sleep.

Sleep is a balancing act. Too little sleep can impact physical and mental health, increasing the risk for a number of diseases and hampering your daily functioning. You might be surprised to learn that too much sleep can have a similar result. Oversleeping has been shown to increase the risk for cardiovascular disease, diabetes, stroke, obesity and cognitive impairment.

Sleep has an impact on depression. There is a clear link between sleep and depression as well. 60-80% of patients with depression report experiencing sleep disturbances of some kind. Persistent sleep problems can significantly increase the risk of a relapse of depression, and may also delay your response to treatment.

Want to improve the quantity and quality of your sleep? Click here for suggestions for sleeping better.