Sleep is a necessity. Failure to get enough sleep has serious side effects. Lack of sleep can cause negative hormonal changes and interfere with the metabolizing of glucose, increase blood pressure and suppress the immune system. Less sleep also means less human growth hormone in your body, which means less muscle mass and weaker bones. Mentally, the brain is impacted as the ability to pay attention and concentrate begins to diminish. Over an extended period, there are psychological effects like paranoia and even hallucinations.