UNC Health Care
rows of prescription bottles

How Over-the-Counter Sleep Aids Can Hurt Your Brain

Over-the-counter sleep aids are marketed as a safe, effective and non-habit-forming way to get some zzz’s when sleep seems hard to come by. But what are the long-term effects on your brain? We asked Dan Kaufer, MD, a neurologist and director of the UNC Memory Disorders Program.

Are over-the-counter sleep aids safe? What effects do they have on your brain?

There are three classes of medications that are notorious for causing cognitive side effects. The most common one is benzodiazepines, which includes Valium and Xanax. These are prescribed to treat anxiety and sometimes sleep. Drugs in this class are generally not recommended for long-term use as a sleep aid because they can impair memory and require higher doses over time to achieve the same effect. The other class of medications is narcotic analgesics. These are getting a lot of attention right now—like hydrocodone or oxycodone—because they are very addictive.

Another drug class people don’t realize may undermine brain health is antihistamines. They are commonly used to treat allergies and are generally safe. However, one of these drugs, Benadryl (diphenhydramine), is commonly used in over-the-counter sleep agents. Taking an over-the-counter sleep aid with diphenhydramine once in a while is generally not going to cause problems, other than a possible hangover the next day.

Older people, however, can get confused when taking diphenhydramine because it also blocks a brain chemical called acetylcholine, which plays a big role in attention and short-term memory. Taking diphenhydramine over a long period of time can actually predispose people to dementia. You should be careful not to use these types of medicines all the time in order to get good sleep.

Does that mean it’s not safe to take over-the-counter antihistamines to treat allergies? The pollen is everywhere, and I can’t stop sneezing!

There are different antihistamines, and Benadryl (or diphenhydramine) is among the worst in terms of cognitive side effects. Other types of antihistamines are used to treat allergies, but none of them are used in sleep aids. It’s important to find one that allows you to function well and control your allergy symptoms. The best way to do that is to consult your physician.

Why is a good night’s sleep so important to overall brain health?

One of the things we’re learning more about is that neurocognitive disorders arise from little perturbations in brain metabolism that lead to the gradual buildup of protein deposits over many years. Exposure to diphenhydramine over the short term can make older folks a little squirrely, but long-term use over many years may lead to Alzheimer’s disease.

If people are unable to achieve a good night’s sleep, they really need to consult with a physician. We’re learning more and more how important sleep is for not just short-term brain functioning, but for long-term brain functioning as well.

One of the current theories about what contributes to the development of neurodegenerative disorders is the accumulation of toxic substances in our brains over many years. We’ve learned that sleep plays a role in eliminating these toxic substances. One of the consequences of not getting enough sleep is that these substances stay in the brain and cause a little bit of damage, which, multiplied over many years, can lead to a neurodegenerative disorder.

So a good night’s sleep isn’t just important for how you do the next day, but not sleeping well over a long period of time can have very dire consequences.

Is there anything I can take safely if I’m having trouble getting sleep?

If sleep is a problem, there are several things people can do. There are other natural products people can take to help them get some sleep, such as melatonin. As far as we know, melatonin in general is a perfectly good substitute for diphenhydramine. It’s a natural supplement. It’s the chemical in the brain that actually induces sleep in a natural way.


If you’re having trouble sleeping, talk to your doctor about enrolling in a sleep study. We have locations in Chapel Hill or Wake County.