Sleep

Sleep was a state of unconscious rest needed by a wide variety of species across the Galaxy, including Humans, Hutts, Gamorreans, Bothans, and Kaleesh. Interestingly, Gand required a fraction of the sleep Humans did, an ability that helped save Ooryl Qrygg's life on Talasea. The Bith race of Clak'dor VII also did not sleep. Instead, they would enter a trance, during which they were almost as aware of their surrounding as awake while receiving the same amount of rest as sleeping species do when asleep. Humans and other species typically slept at night, and it was considered a necessity for proper functioning and personal performance. Lack of sleep would induce less effective performance and a bedraggled appearance in Humans, although other species might manifest a lack of sleep differently.

REM sleep was a stage of sleep necessary to most beings. If a person did not get the acquired amount, there could be repercussions, ranging from depression, exhaustion and hallucinations all the way to a possible psychotic break.

Droids could, in a manner of speaking, also sleep when they entered a powered-down state from time to time.

Reportedly, Darth Sidious killed his Master Darth Plagueis while the latter was sleeping. Afterwards, Sidious himself did not sleep, determined not to make the same mistake as his master, possibly relying on the power of the dark side of the Force to sustain himself. Similarly, as Bane grew more powerful in the dark side during his studies at the Sith Academy on Korriban, he almost never slept. He found that it seemed his body no longer needed sleep, feeding on his growing command of the dark side. He relied instead on an hour or two of meditation each day to keep his body energized and his mind invigorated. Nevertheless, even this power had its limits. After wandering for nearly two weeks in the wastelands of Korriban with no sleep whatsoever, Bane returned to his room at the Academy and dropped into a deep, dreamless sleep within seconds that lasted for several hours.

Text and facts from the “Sleep/Legends” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.