Caffeine, Alcohol, Nicotine, and Other Substances

Caffeine, alcohol, nicotine, cannabis, and other substances can affect how we sleep and how alert we feel throughout the day. Some help us stay awake, while others make it easier to fall asleep. However, they can also change how long we sleep, disrupt our sleep quality, or interfere with our natural sleep-wake rhythms.

Understanding these effects can help us make more informed choices about what we consume and when. Even small changes in our habits can help protect sleep and support our health and wellbeing across all 24 hours.

Substances can affect more than sleep. Some carry risks of dependence, interact with medications, or worsen existing health conditions. Some substances are available without restrictions, others are restricted to adults aged 21 or older, and some require a prescription or are illegal. Laws vary between countries and regions, and legal status does not necessarily mean a substance is safe.

Some substances can also cause withdrawal symptoms when use is reduced or stopped. If you are concerned about your substance use, a healthcare professional can help you find appropriate support.

Combining substances can increase their risks, particularly when alcohol, opioids, or other sedating drugs are used together. Using one substance to counteract the effects of another, such as taking a sleep aid after using stimulants, can also be dangerous. These combinations can affect breathing, alertness, and overall health, even when the individual substances are legally available or prescribed.

In the United States, free and confidential support is available through the SAMHSA National Helpline at 1-800-662-HELP (4357). For help quitting nicotine, call 1-800-QUIT-NOW (1-800-784-8669).

Caffeine is found in coffee, tea, energy drinks, and many other products. It helps us feel more alert by blocking adenosine, a chemical in the brain that builds up while we are awake and makes us feel sleepy.

However, caffeine can remain active in the body for many hours. Consuming it too close to bedtime can make it harder to fall asleep, shorten sleep, and reduce deep sleep. Research suggests that higher doses can affect sleep even when consumed up to 12 hours before bedtime. People do not always notice these changes in their sleep.

The effects depend on how much caffeine we consume, when we consume it, and how sensitive we are to it. There is no need for most people to give up coffee or tea, but limiting caffeine later in the day can help protect sleep. If you need an afternoon energy boost, try a short walk, natural daylight, or a caffeine-free drink.

Nicotine is a stimulant found in cigarettes, vapes, and other tobacco and nicotine products. Although smoking can feel relaxing, nicotine can interfere with sleep. Research has linked regular nicotine use with more light sleep, less deep sleep, and more time spent awake during the night. This can leave people feeling less rested, even if they do not notice a significant change in their sleep quality.

Nicotine cravings can also interrupt sleep, while cutting back or quitting may temporarily cause sleep difficulties as the body adjusts to withdrawal. These symptoms generally improve over time. A healthcare professional can help manage withdrawal symptoms and provide support for quitting.

Many people drink alcohol to relax or help them fall asleep. Alcohol can make us feel sleepy and, particularly at higher amounts, shorten the time it takes to fall asleep. However, falling asleep faster does not necessarily mean sleeping better.

Research shows that even moderate amounts of alcohol can reduce and delay REM sleep, an important stage involved in memory and emotional processing. These effects tend to increase with the amount consumed. Alcohol can also disrupt sleep later in the night as its effects wear off.

If alcohol is part of your evening routine, consider replacing it with a non-alcoholic drink or finding other ways to unwind before bed. If you regularly rely on alcohol to fall asleep, a healthcare professional can help you explore alternatives and improve your sleep.

Cannabis, also known as marijuana, is commonly used to help with sleep. Many people report that it helps them relax, fall asleep faster, or sleep more comfortably, particularly when pain or anxiety makes sleeping difficult. Some clinical studies have also found improvements in sleep quality, although results vary between products and individuals.

Cannabis contains several active compounds, including THC (tetrahydrocannabinol) and CBD (cannabidiol), which affect the body differently.

THC is the main intoxicating compound in cannabis. It can cause drowsiness and help some people fall asleep. However, its effects on sleep stages are less clear. Some studies have found reductions in REM sleep, while others have reported little or no change. The effects appear to depend partly on the dose and product used.

CBD does not cause the intoxication associated with THC. Some people use it to promote relaxation or manage symptoms such as anxiety and pain that interfere with sleep. However, research has not consistently shown that CBD alone improves sleep.

Although cannabis may offer sleep benefits for some people, it is not yet an established treatment for insomnia. Studies have produced mixed results, and more research is needed to understand its long-term effects. Regular use can also lead to dependence, and reducing or stopping cannabis may temporarily cause difficulty sleeping, vivid dreams, or changes in REM sleep.

If you are considering cannabis for sleep, talk with a healthcare professional about its potential benefits, risks, and interactions with other medications.

Opioids are powerful medications used to treat certain types of pain. They include prescription medicines such as morphine and oxycodone, as well as illicit opioids such as heroin. Although opioids can cause drowsiness, feeling sleepy does not necessarily mean getting healthy, restorative sleep.

Opioids can disrupt normal sleep patterns and interfere with breathing during sleep. They can slow or suppress breathing and increase the risk of central sleep apnea, a condition in which the brain temporarily stops sending signals to breathe. These effects can be dangerous, particularly at higher doses or when opioids are combined with alcohol, benzodiazepines, or other sedating substances. Such combinations can cause life-threatening breathing problems and overdose.

Long-term opioid use can also lead to physical dependence, and withdrawal often causes significant sleep difficulties. People taking prescribed opioids should discuss sleep problems, loud snoring, or breathing pauses with their healthcare professional rather than changing their medication on their own.

Warning: Opioid overdose is a medical emergency. If someone is unresponsive, difficult to wake, or breathing very slowly or irregularly, call 911 immediately (in the United States). Administer naloxone if available and stay with the person until emergency help arrives.

Stimulant drugs, including cocaine, methamphetamine, and amphetamines, increase alertness and activity in the nervous system. They can delay sleep, reduce total sleep time, and interfere with deep, restorative sleep. People may remain awake for extended periods, followed by extreme tiredness or prolonged sleep as the effects wear off.

Nonmedical use of these drugs carries serious health risks, including dependence, heart problems, and potentially life-threatening complications. Regular use can severely disrupt sleep patterns, while withdrawal can cause excessive sleepiness, fatigue, and persistent sleep difficulties. Combining stimulants with alcohol or other substances adds further risks.

Some stimulants, including methylphenidate and amphetamine-based medications, are prescribed to treat conditions such as ADHD. When used as directed, they can be effective treatments, but they can also interfere with sleep, particularly if the dose or timing is unsuitable. If a prescribed stimulant is affecting your sleep, talk with your healthcare professional about possible adjustments rather than changing your medication on your own.

If you regularly rely on alcohol, cannabis, or other substances to fall asleep, or find it difficult to cut back, consider speaking with a healthcare professional. Getting help is also important if substance use is affecting your sleep, daily functioning, or overall health.

A healthcare professional can help identify how substance use, medications, and underlying health conditions may be affecting your sleep. Together, you can explore ways to improve sleep while addressing any concerns about substance use.

Improving sleep does not require making every change at once. Finding the right support and making manageable adjustments can help protect your sleep and wellbeing across all 24 hours.