Lack of Sleep Leads to Negative Emotions and Depression
Not only does a lack of sleep impair your ability to make smart decisions, it also causes your mind to mimic the feelings and effects of depression. It's proven that a lack of sleep has an immediate effect on mood, with sleep-deprived people both feeling and showing less positive emotion. When you're feeling negative, you'll be far less capable of dealing with any issues that arise, and far more likely to let these issues overwhelm you, because sleep deprived people are proven to be less capable of dealing with short term negative emotions.
Lack of sleep affects memory, learning and retention
Sleep is vitally important to memory, because it's the time when our minds filter out the non-essential and lay down the neural pathways that reinforce what we learned the day before. But multiple studies on mice show that a single night of bad sleep leads to a loss of connectivity in the parts of the brain responsible for learning and memory. Even worse, long term sleep deprivation led to an increase in amyloid plaques, which have a direct link to dementia and Alzheimer's disease.
Obviously, these long-term concerns are huge, but in the short term, lack of sleep also contributes to a problem with retaining and recalling information. So if you're put on the spot and forced to make a snap decision, it increases the chances that you'll recall the wrong thing and make bad decisions.
Lack of sleep affects levels of testosterone and other hormones
Studies show that just one night of bad sleep can drop blood testosterone levels by as much as 15%, with longer term sleep deprivation leading to an even greater impact. Considering testosterone is has a direct and measurable effect when it comes to mood regulation, ability to deal and respond to outside stressors, ability and speed of decision making, ability to lead, as well as physical health, fitness and muscle growth, this single reason alone is enough to consider getting an earlier night.
Lack of sleep also leads to long-term health problems
You're in this for the long haul. Or at least, you should be. So when sleep deprivation has been linked to serious medical problems like heart disease and diabetes, it's just not the smart play. Lack of sleep and the hormone issues that come with it also contribute to weight gain, which leads to its own complications.