Which substance, when consumed in large quantities, can trigger a sleep disorder related to REM sleep?

The correct answer is alcohol. When consumed in large quantities, alcohol disrupts the normal sleep cycle, particularly impacting REM sleep. Although initially, alcohol may appear to have a sedative effect, it ultimately leads to a reduction in the amount and quality of REM sleep throughout the night. This disruption can cause fragmented sleep, increased awakenings, and an overall decline in sleep quality.

As for the other options, caffeine acts as a stimulant and is more likely to delay sleep onset and reduce total sleep time, rather than specifically disrupting REM sleep. Nicotine, while it can also affect sleep patterns by reducing overall sleep time, primarily impacts sleep architecture rather than just REM sleep. Sugar, on the other hand, is not directly linked to sleep disorders related to REM sleep, but can cause fluctuations in energy and may lead to disturbances in sleep due to its effects on overall health and metabolism.