A potential side effect of z-drug hypnotics is "complex sleep-related behaviors". These are parasomnias where the person gets out of bed and performs activities while in an altered state of consciousness that may be called sleep, and is certainly not waking. The complex behavior may include sleep walking or eating and even driving a car.
The Z-drugs produce this side effect more often than the old-style barbiturates and benzodiazepines did. (Which is one reason that although these Z-drugs are safer, they should still be used with caution.) The labels on the medicines tell patients to take the pills only before bed when they can devote the next 8 hours to being in bed.
The term z-drug zombie is informally used to refer to people doing these behaviors under the influence of these drugs. This usage may have caught on partly because zombie starts with the letter z and the generic name for these drugs contain the letter z in them. Another term used is Ambien Zombie when the behavior is seen in those who take zolpidem (Ambien).
Hallucinogens are relatively common in people who take these drugs, which increases the creepiness factor. Even if the subjects don’t act like zombies themselves, they might think they are seeing zombies. Patients often describe it as having a dream while awake, a good description of a parasomnia.
Driving is the greatest concern when it comes to Z-drug zombie behavior. Sleep driving is potentially worse than drowsy driving or drunk driving. Indeed, even when the driver isn’t asleep residual hypnotics in the bloodstream can impair the driver’s vigilance and performance. Indeed toxicology labs show zolpidem as one of the most common drugs found in drivers arrested for impaired driving.
There are even reports of people intentionally taking Ambien while they are away from home before getting in the car, out of the belief that it will “kick-in” later when they are ready for bed. This is a very dangerous practice and should be discouraged.
Sleep eating might seem harmless, but while impaired the person may eat raw foods that should be cooked before consumption. Other dangerous activities that have been reported include going outside in very cold weather with little clothing, using the oven or stove with no concern for getting burned, risking falling out of windows or off ledges, and painting the walls and becoming exposed to paint fumes.
Zolpidem loses its efficacy in some insomniacs after a few weeks, which drives some to increase their dosage, with or without their doctor’s approval. (The FDA recommends limiting zolpidem to only a few weeks at most.) This increase makes it more likely the person will experience a z-drug zombie incident.
Scientists do not understand any biochemical reason the drug should promote these unusual behaviors.
One silver lining in the z-drug zombie phenomenon is that it might end up providing insight into brain disorders. The weirdness could suggest avenues for research into neurological disorders.
How are zombies portrayed in popular film and television? It could be argued that they look like people with very serious insomnia. They never sleep and walk around in a daze. A blogger at Scientific American has fancifully suggested the zombies have a severe circadian disorder in which their bodies are always switched to the daytime mode.