Sleep problems, including snoring, sleep apnea (stops in breathing during sleep), insomnia (difficulty falling asleep and/or staying asleep with no obvious cause), sleep deprivation, and restless legs syndrome, are common. Good sleep is necessary for optimal health and can affect hormone levels, mood and weight. Sleep disorders interfere with normal physical, mental, social and emotional functioning. Management of sleep disturbances that are secondary to mental, medical, or substance abuse disorders aims to focus on the underlying conditions.