Side effects are uncommon, but may include headache, nausea or anxiety. There is no cure, but treatments such as medication and scheduled naps can reduce some of its effects. This disorder is extremely unpredictable and can be dangerous. Narcolepsy isn't a deadly disease by itself, but episodes can lead to buy modafinil, injuries, or life-threatening situations. Many cases of narcolepsy are thought to be caused by a lack of the brain chemical hypocretin (also known as orexin), which regulates sleep. In addition, questionnaires, such as the Epworth Sleepiness Scale, are often used to measure excessive daytime sleepiness. This deficiency is thought to result from the immune system mistakenly attacking parts of the brain that produce hypocretin. People with narcolepsy usually feel rested after waking, but then feel very sleepy throughout much of the day. Narcolepsy is a chronic neurological disorder that affects the brain's ability to control sleep-wake cycles.