Insomnia is defined as difficulty initiating or maintaining sleep or not feeling rested after sleep. Up to 30% of the general population reports experiencing sleep disturbances. In clinical settings, up to 50% of patients complain of sleep-related problems. According to the International Classification of Sleep Disorders, there are 11 types of insomnia.The three most common are adjustment insomnia, psychophysiologic insomnia, and insomnia secondary to a mental disorder.