Somnolence: is a state of sleepiness where you’re close to falling asleep, and may not be able to resist the urge to doze off. As someone in treatment for bipolar disorder or another mental illness, this can affect you since many psychiatric medications (and many non-psychiatric medications, too) can cause somnolence.
Sometimes called “Daytime Sleepiness”, it can make people feel compelled to nap repeatedly during the day, often at inappropriate times such as at work, during a meal, or in conversation. These daytime naps usually provide no relief from symptoms. Somnolence is a medical term, but there are many other terms for the same state of sleepiness including drowsiness, lethargic, insensible and just plain sleepy.