For people who live with bipolar disorder, depression and oversleeping go hand in hand. The cause and effect go in both directions. Depression often leads to sleeping more and to a delayed sleep pattern (staying up later and sleeping later); sleeping longer and later can cause or worsen depression. Fortunately, the downward cycle of depression and oversleeping can run in the opposite direction. Reducing hours of sleep and waking early in the morning can have a very strong antidepressant effect.
As you point out, sleeping less and waking earlier is easier said than done. It is important to realize that oversleeping is not just laziness. Depression creates a strong pressure to sleep more and sleep later. But there are a few specific things that can help.
Setting a regular waking time is the most important step. People who are struggling with a delayed sleep pattern often feel, “I could wake up earlier if only I could get to sleep earlier.” But we know that biology actually goes in the other direction: “I could get to sleep earlier if only I could get up earlier.”
When people spend many hours in bed, their sleep is often interrupted—with short periods of sleep and lots of time lying in bed awake. That type of sleep is not at all restful. It’s natural to think, “I need to spend more time in bed to feel rested.” Once again, the biology of sleep goes in the other direction: spending fewer hours in bed will lead to less interrupted—and more restful—sleep.
Bright light and activity early in the day can help to reset a delayed sleep pattern. During spring and summer, it’s enough to open the shades early and get outdoors in the morning. Natural light will send a strong morning signal to your brain and shift your sleep pattern earlier. In the fall and winter months, it may take a bright light box to send a strong enough morning signal. I should warn that there are reports of people with bipolar disorder feeling speeded up or manic after using a bright light box—but that’s also evidence that it really can work!