A drink before bed has long been considered a way to unwind and fall asleep faster. But research on how alcohol affects sleep tells a different story.

We also know more about drinking and healthy aging. And alcohol isn't the only culprit. Caffeine, even earlier in the day, and certain medications, even when prescribed by a doctor, can also interfere with quality sleep. In these cases, even the best mattress, a dark room, and a white noise machine may not be enough to guarantee a good night's rest.

When natural sleep remedies fail, understanding how substances affect sleep may help. Read on to learn more about how alcohol, caffeine, and common medications affect sleep. 

Substances That Affect Sleep at a Glance

What is the sleep-wake cycle?

The sleep-wake cycle is your body's natural system for knowing when to be awake and when to sleep. Understanding this cycle is an important part of learning how substances affect sleep. Many common drinks, medications, and drugs can interrupt the process and make it harder to get quality rest.

“Sleep is not the brain simply shutting off,” said Frank Spinelli, MD, internist and addiction specialist with Reframe in Alpharetta, Georgia. “It is an active process. Sleep happens because several systems shift together from promoting alertness to allowing the brain to move through its normal sleep stages.” 

One system involves your body's internal clock, which responds to light and darkness. As daylight fades, your brain releases the hormone melatonin. It helps prepare your body for sleep. During the day, a chemical called adenosine builds up in your brain, making you feel sleepier the longer you stay awake. This is known as "sleep pressure." When you sleep, those adenosine levels fall so you wake up feeling refreshed. Another important part of this process is a brain chemical called gamma-aminobutyric acid (GABA). It helps quiet the brain by slowing down the signals that keep you alert.

Common substances that can affect your sleep-wake cycle:

• Alcohol
• Caffeine
• Nicotine
• Prescription stimulant medications
• Some antidepressants
• Certain cold and allergy medicines
• Prescription and over-the-counter sleep aids

Each of these substances affects the brain in different ways. This is why it's important to understand how alcohol, caffeine, and different medications affect sleep.

How do substances disrupt sleep?

“What we put into our bodies can absolutely change our brain chemistry and the way we sleep,” said Dr. Spinelli. “Some medications are activating whereas others are sedating, so they can push the brain in either direction. And the way they impact the brain can change depending on other things we ingest.” 

The sleep center of your brain is controlled by chemicals called neurotransmitters. These chemicals send messages between nerve cells and help control when you feel alert or sleepy. Some neurotransmitters, like dopamine, increase alertness and make it harder to fall asleep. Others, like GABA, help calm the brain and support sleep. Different substances affect these brain chemicals in different ways. They can change both how quickly you fall asleep and how well you stay asleep. Understanding how substances affect sleep starts with understanding how these chemicals work together.

How caffeine affects sleep is closely tied to adenosine, the chemical that builds sleep pressure throughout the day. "Caffeine blocks adenosine," said Michael DeShields, MD, clinical advisor at Discovery Institute, a drug and alcohol rehab facility in Marlboro, New Jersey. As a result, you don't feel sleepy. Other substances like nicotine and prescription stimulant drugs keep the brain on high alert. This prevents you from feeling tired.

How alcohol affects sleep is more complicated. Alcohol is a depressant and may make you feel drowsy at first. But it often causes lighter, more broken sleep later in the night. “Sleep-enhancing medications also help people fall asleep, but are not the same as restful sleep,” said Dr. DeShields. “Many prescription sleep aids will initially make you feel more relaxed, but they have been known to disrupt sleep patterns throughout the remainder of the night.” Understanding how these substances affect the brain can help you spot habits or medications that may disrupt sleep.

Common substances that affect sleep

Many common substances change the way the brain works. Some make you feel sleepy at first, while others keep your brain alert. Even medications designed to help you sleep can sometimes make it harder to get a good night's rest. Here is a closer look at some common substances that affect sleep.

Alcohol

“While alcohol does make people feel drowsy, it does not help with sleep,” said Dr. Spinelli. “In fact, it actually prevents normal, restful sleep.”

This happens because alcohol is a depressant that slows brain activity. This is why it can feel calming. “It increases the effects of gamma-aminobutyric acid (GABA), one of the brain’s main calming chemicals, and reduces the activity of glutamate, which helps keep us alert,” said Dr. Spinelli. “But the brain tries to compensate. As the alcohol is metabolized, that calming effect fades and brain activity can rebound.”

That, he said, is when people may become restless. They may wake up frequently and have trouble falling back asleep, or have unusually vivid dreams. This often leaves people feeling fatigued the next day even though they were in bed all night. It also interrupts REM sleep. This is the stage that is important for memory and emotional processing.

What’s more, Dr. Spinelli said, “Age makes all of this more noticeable. Older adults metabolize alcohol more slowly, have less body water to dilute it, and are more likely to take medications that interact with alcohol.” 

Stimulants

Many people think of coffee when they hear the word stimulant, but there are several kinds. Caffeine increases alertness and keeps the brain awake. It can be found in:

• Coffee
• Tea
• Energy drinks
• Foods including chocolate

“Caffeine blocks adenosine, the chemical mentioned above that builds sleep pressure throughout the day,” said Dr. Spinelli. ADHD medicines work in a similar way because they are also stimulants. 

How much caffeine you consume matters, but so does timing. "The amount of time that passes after consuming caffeine is important when determining a cut-off point for consumption prior to bedtime," said Dr. DeShields. "This time frame ranges from 6–8 hours, depending on your body's sensitivity to caffeine." If you take ADHD medication or another stimulant and it is affecting your sleep, talk to your prescribing physician about adjusting the dosage or timing.

Blood pressure medicines

Some blood pressure medicines can change the way the body and brain work during sleep. Depending on the type of medicine, they may make it harder to fall asleep or cause you to wake up during the night. Others may affect dreams or leave you feeling less rested in the morning. One specific kind of blood pressure medication called beta-blockers may affect sleep-producing hormones, making it more difficult to fall and stay asleep.² 

Another kind of blood pressure medicine is known as a diuretic. These make you need to use the bathroom more often, which can disrupt sleep. But some research has shown that diuretics may actually reduce the severity of sleep apnea in people with high blood pressure.³ If you suspect your blood pressure medicine is interfering with your sleep, discuss it with your doctor.

Antidepressants

Antidepressant use increases with age and is highest among women aged 60 and over (24.3%).⁴

Antidepressants work by changing the levels of certain brain chemicals that affect mood. Those same chemicals also help control your sleep cycle. Because of this, some antidepressants may make you feel sleepy. Others may make it harder to fall asleep or stay asleep.

The effects can be different from one person to another. Some people notice more vivid dreams or changes in REM sleep. Others find that their sleep improves as their mood gets better. If an antidepressant is affecting your sleep, your doctor may be able to adjust the dose or the time you take it.

Cough and cold medications

Cough and cold medicines can affect sleep in different ways depending on the ingredients. Some contain antihistamines that make you feel sleepy. Others include decongestants such as pseudoephedrine that can make you feel more awake. Reading the label can help you know what to expect.

Even medicines that cause drowsiness may not lead to restful sleep. "Antihistamines can create drowsiness during the night, but many times leave individuals feeling groggy upon waking," said Dr. DeShields. If you often need cold medicine, ask your health care provider which option may have the least effect on your sleep. And if you notice changes in your sleep after starting a new medicine, talk with your health care provider before making any changes.

Nicotine

Nicotine is another stimulant that affects the brain. It increases alertness and raises your heart rate, making it harder to relax before bed. Even if you feel tired, nicotine can delay sleep and make it more difficult to stay asleep. The effects continue after the nicotine wears off. "Nicotine has a stimulating effect on the body until it wears off at night," said Dr. DeShields. "Because of this cycle of stimulation and withdrawal, it is common for individuals who smoke to experience difficulty falling asleep."

While smoking rates have dropped in the United States overall, those among adults 65 years and older have increased by more than half a million in recent years.^5,6  There are roughly 4.6 million older adult smokers in the United States, more than any other age group.⁶

Healthier sleep is one of the many good reasons to quit smoking. 

Anti-insomnia medications and overuse

Older adults tend to use sleep aids more than any other age group. Nearly 16% of those age 65 and older report daily or almost daily use.⁷  There are both prescription and over-the-counter products to help with sleep. But neither is intended to be a long-term solution. “Sleep-enhancing medications help people fall asleep, but are not the same as restful sleep,” said Dr. DeShields. “Many prescription sleep aids will initially make you feel more relaxed. However, they have been known to disrupt sleep patterns throughout the remainder of the night.”

Melatonin is one of the most common non-prescription sleep aids. It works by adding to the body’s natural melatonin, a hormone that helps control the sleep-wake cycle. Research suggests it may provide modest benefits for some sleep problems, especially certain circadian rhythm disorders.⁸ Melatonin is also generally considered safe when compared with many prescription medicines. Still, experts know much less about the long-term safety of using melatonin. Melatonin should be treated like a medication, not a harmless supplement. It can interact with other medicines and health conditions.

Another concern is that melatonin supplements can vary in strength, especially when sold as a dietary supplement. Taking more is not always better, and experts recommend using the lowest effective dose. It should usually be taken about 30–60 minutes before bedtime to reduce the chance of next-day drowsiness. If you are considering melatonin or another sleep aid, talk with your doctor first. Especially if you have liver disease, balance problems, low or high blood pressure, or take several medications.

Prescription sleep medicines may be the right choice for some people, but only a doctor can decide if they are appropriate. “Treatment for insomnia begins by addressing underlying issues, such as sleep apnea, depression, chronic pain, prescription drug side effects, or substance abuse,” said Dr. DeShields. If you can’t sleep due to pain, you may benefit from one of the best mattresses for back pain or one of the best mattresses for neck pain. 

How to talk to your doctor about sleep concerns

If you are having trouble sleeping, be honest with your doctor about everything that could be affecting your rest. The goal is to find the real cause, whether it is how alcohol affects sleep, how caffeine affects sleep, or medications that affect sleep. "The question both you and your doctor are trying to solve is, 'What is interfering with my sleep in the first place?'" said Dr. Spinelli.

To answer this, there are several possibilities that must be discussed. Be open about all the experiences you're having at night. This could include frequent bathroom visits, sleep apnea, or restlessness. You should also come prepared with a list of every substance you take. This list should include prescriptions, over-the-counter medications, supplements, alcohol, caffeine, nicotine, and other substances. "Often, people forget to mention a daily allergy pill or a nightly glass of wine, but those can affect sleep quality," said Dr. Spinelli.

Here are some of the questions you may want to ask:

• Could one of my medications be affecting my sleep?
• Should I be tested for a sleep disorder like sleep apnea?
• Would changing when I take my medicine help?
• Is melatonin or another sleep aid right for me?
• What lifestyle changes could improve my sleep before trying medication?

Frequently asked questions 

What time of day is the latest I should drink coffee?
Most experts recommend avoiding caffeine for at least 6–8 hours before bedtime. The exact timing depends on how sensitive your body is to caffeine.

What questions should I ask my doctor if my sleep is often disrupted?
Ask what might be causing your sleep problems, whether your medications could be playing a role, and if you should be evaluated for a sleep disorder. You should also bring a list of all prescription medicines, over-the-counter products, supplements, and substances you use.

What are the most common sleep disorders?
Some of the most common sleep disorders include insomnia, sleep apnea, restless legs syndrome, and circadian rhythm sleep-wake disorders. Each has different causes and may require different treatments.

What is the safest sleep medication to take?
There is no single sleep medication that is safest for everyone. Your doctor can help choose the best option based on your health, symptoms, and the cause of your insomnia.

How can you tell if you are getting quality sleep?
You are more likely getting quality sleep if you fall asleep without much trouble, stay asleep most of the night, and wake up feeling rested. If you are always tired during the day despite spending enough time in bed, talk with your doctor.

Sources

1. National Institute on Alcohol Abuse and Alcoholism. Alcohol and Older Adults Ages 65+. August 2025. Found on the internet at https://www.niaaa.nih.gov/alcohols-effects-health/alcohol-topics-z/alcohol-facts-and-statistics/alcohol-and-older-adults-ages-65 

2. Riemer T.G., et al. Do β-Blockers Cause Depression? Systematic Review and Meta-Analysis of Psychiatric Adverse Events During β-Blocker Therapy. Hypertension. March 15, 2021. Found on the internet at https://www.ahajournals.org/doi/10.1161/HYPERTENSIONAHA.120.16590 

3. Zeng Z., et al. Effect of antihypertensive medications on sleep status in hypertensive patients. Sleep and Biological Rhythms. May 18, 2022. Found on the internet at https://link.springer.com/article/10.1007/s41105-022-00391-8

4. Brody D.J., Gu Q. Antidepressant Use Among Adults: United States, 2015-2018. National Center for Health Statistics. September 2020. Found on the internet at https://www.cdc.gov/nchs/products/databriefs/db377.htm

5. Kleykamp B.A., Kulak J.A. Cigarette Use Among Older Adults: A Forgotten Population. American Journal of Public Health. Oct. 10, 2022. Found on the internet at https://ajph.aphapublications.org/doi/abs/10.2105/AJPH.2022.307151?journalCode=ajph

6. Arrazola R.A., et al. Notes from the Field: Tobacco Product Use Among Adults - United States, 2017-2023. Morbidity and Mortality Weekly Report. March 6, 2025. Found on the internet at https://www.cdc.gov/mmwr/volumes/74/wr/mm7407a3.htm?s_cid=mm7407a3_w

7. Mykyta L., et al. Use of Sleep Aids Among Adults Age 18 and Older: United States, 2024. National Center for Health Statistics. April 2026. Found on the internet at https://www.cdc.gov/nchs/data/hestat/hestat116.htm

8. Tuft C., et al. Current Insights into the Risks of Using Melatonin as a Treatment for Sleep Disorders in Older Adults. Clinical Interventions in Aging. Jan. 12, 2023. Found on the internet at https://www.dovepress.com/current-insights-into-the-risks-of-using-melatonin-as-a-treatment-for--peer-reviewed-fulltext-article-CIA