Many people don’t realise how much the things we put into our bodies, whether prescribed by a doctor or used recreationally, can influence sleep. Some substances make you drowsy, others keep you awake, and many change the natural balance of sleep stages that your brain and body need to recover.
Common Substances That Affect Sleep
Alcohol
- Alcohol makes it easier to drift off, but it blocks REM sleep while it’s in your system.
- This means you get little or no dream sleep in the first half of the night, then your body tries to catch up later, leading to a disrupted sleep cycle.
- Alcohol also relaxes throat muscles, which can worsen snoring and sleep apnoea (OSA).
Caffeine
- Found in coffee, tea, chocolate, and energy drinks.
- Blocks the brain’s natural “sleep pressure” chemical (adenosine), keeping you alert.
- Even 6–8 hours before bed, caffeine can delay sleep and reduce deep, restorative sleep.
Nicotine
- Many people use nicotine for its calming effect, but physically it acts as a stimulant.
- It makes it harder to fall asleep, shortens sleep, and fragments rest.
- Overnight withdrawal can also cause awakenings.
Cannabis
- THC helps some people fall asleep but suppresses REM sleep while in your system — meaning the first half of the night has little dream sleep. This disrupts the natural REM cycle.
- CBD has more mixed research; it may mildly help with sleep (especially when treating anxiety) but effects vary.
- Long-term or heavy use can reduce sleep quality, and stopping suddenly often causes rebound insomnia.
Comparing Common Sleep Medications
Even medications prescribed to help sleep can sometimes hinder it. Many sleeping pills change the natural structure of sleep (reducing deep or REM sleep) so while they may help you fall asleep, the rest you get may not feel refreshing or be as restorative.
| Medication Type | Examples | Effect on Sleep | Risk of Dependence | Typical Recommended Use | Notes |
| Benzodiazepines | Temazepam, Diazepam | Help with falling asleep, but reduce deep & REM sleep. | High – tolerance and dependence common. | Short-term only (2–4 weeks), not nightly. | Can worsen obstructive sleep apnoea due to muscle relaxation. Sleep may feel lighter and less restorative. |
| Non-benzodiazepines (Z-drugs) | Zolpidem, Zopiclone, Eszopiclone | Shorten time to fall asleep, but still suppress REM sleep. | Moderate – dependence and rebound insomnia possible. | Short-term (2–4 weeks max), ideally “as needed” a few nights/week. | Designed to be safer than benzos, but can still reduce natural sleep quality. |
| Sedating Antidepressants | Amitriptyline, Doxepin, Mirtazapine | Improve sleep continuity, may increase deep sleep but reduce REM. | Low–moderate – less addictive, but tolerance and side effects possible. | Sometimes used longer-term if treating depression/ anxiety too. | Can cause morning grogginess or weight gain, making sleep feel unrefreshing. |
| Melatonin / Melatonin Agonists | Melatonin, Ramelteon | Help regulate circadian rhythm, minimal effect on sleep stages. | Very low – no true dependence. | Can be used longer-term. | Best for jet lag, shift work, or circadian rhythm issues, not general insomnia. |
| Over-the-counter Antihistamines | Diphenhydramine, Doxylamine | Sedating; may help with sleep onset. | Low for dependence, but tolerance develops quickly. | Short-term or occasional use. | Often cause a “hangover effect” the next morning; not recommended long-term. |
| Other Prescription Options | Orexin antagonists (suvorexant, lemborexant) | Promote more natural sleep by blocking “wake signals.” | Low–moderate. | Can be used longer-term under supervision. | Newer class; may avoid some of the pitfalls of older sleep medicines. |
Other Prescription Medications That Affect Sleep
Almost any prescription drug that acts on the brain or nervous system can influence sleep; sometimes positively, sometimes negatively. If sleep problems start after a new medication, it’s worth discussing with your doctor.
Antidepressants
- Sedating types (amitriptyline, doxepin, mirtazapine) can improve sleep continuity, but may cause grogginess and weight gain
- Stimulating types (SSRIs like sertraline, fluoxetine) can cause insomnia, vivid dreams, and restless sleep
Stimulant medications (for ADHD, narcolepsy: methylphenidate, amphetamines, modafinil)
- Increase daytime alertness
- If taken late in the day, can cause insomnia and reduced total sleep
Pain and muscle medications
- Opioids reduce pain and help with sleep onset, but suppress REM sleep, fragment rest, and worsen sleep apnoea
- Muscle relaxants (e.g. baclofen, tizanidine) may cause drowsiness but often reduce overall sleep quality
Blood pressure and heart medications
- Beta-blockers (atenolol, propranolol) can reduce melatonin, leading to insomnia and vivid dreams
- Diuretics increase night-time urination, causing frequent awakenings
Steroids (prednisone, dexamethasone)
- Stimulating, often causing insomnia, restlessness, or early waking
- Best taken in the morning to reduce sleep disruption
Antipsychotics (quetiapine, olanzapine, risperidone)
- Sedating, sometimes prescribed “off-label” for sleep
- Can reduce sleep quality, cause grogginess, and lead to weight gain
- Should only be used for sleep under medical guidance
Parkinson’s medications (levodopa, pramipexole, ropinirole)
- Can help with restless legs symptoms that disturb sleep
- May cause insomnia, vivid dreams, daytime sleepiness, or sudden “sleep attacks”
- Can trigger REM sleep behaviour disorder (acting out dreams)
Anti-seizure medications (gabapentin, pregabalin, valproate, carbamazepine)
- Gabapentin and pregabalin often improve sleep continuity
- Others may be sedating but can fragment sleep
- Side effects vary widely depending on the drug
Conclusion
Sleep is shaped by far more than just how long you’re in bed — the substances you use and the medications you take can dramatically affect its quality. While some drugs make you drowsy, many disrupt the natural balance of deep and REM sleep, leaving you feeling unrefreshed. Even everyday substances like alcohol, caffeine, nicotine, and cannabis can alter your sleep cycle in ways you may not notice until you wake up tired.
Prescription medications add another layer of complexity. Sleeping pills, antidepressants, stimulants, pain medications, and even common heart or steroid treatments can either help or hinder your rest. In some cases, substances or medications may even worsen underlying sleep apnoea by relaxing airway muscles.
Because of this, if you are still tired despite medication, if your symptoms don’t improve or worsen with treatment, or if you have risk factors for obstructive sleep apnoea (OSA) such as snoring, morning headaches, or excessive daytime sleepiness, a sleep study is strongly recommended. A sleep study can uncover hidden conditions like OSA or restless legs syndrome that medication alone cannot fix.