Sleep disorders involve problems with the quality, timing and amount of sleep, which cause problems with functioning and distress during the daytime. There are a number of different types of sleep disorders, of which insomnia is the most common. Other sleep disorders are narcolepsy, obstructive sleep apnea and restless leg syndrome. Sleep difficulties are linked to both physical and emotional problems. Sleep problems can both contribute to or exacerbate mental health conditions and be a symptom of other mental health conditions. Sleep is a basic human need and is critical to both physical and mental health. There are two types of sleep that generally occur in a pattern of three-to-five cycles per night Rapid eye movement (REM) – when most dreaming occurs and Non-REM – has three phases, including the deepest sleep.