Sleep deprivation has been linked to an increase in negative emotions (anger, irritation, impatience, and melancholy) as well as a reduction in positive moods, according to research. In addition, sleep deprivation is frequently a sign of mood disorders such as sadness and anxiety. Finally, poor quality sleep has been shown to increase the risk of developing cardiovascular diseases and diabetes. The connection between depression and insomnia has long been recognized; patients with major depressive disorder are at increased risk for developing insomnia. However, recent studies have also shown that insomnia can lead to or exacerbate feelings of depression. It's possible that people with insomnia feel depressed because they're not getting the necessary rest needed to feel refreshed. Here are some other ways in which poor sleep habits may cause or contribute to feeling depressed: You go to bed tired but can't fall asleep right away. This means you're spending most of your time awake thinking about things from the day that make you unhappy or stress out about things you need to do. Not only is this affecting your mood negatively, it's also causing damage to your brain by keeping it active while it tries to fall asleep. You wake up feeling exhausted but can't get back to sleep. If you're waking up every morning feeling drained and unable to get back to sleep, then this is indicative of a larger problem.