Could medicines, alcohol, or cannabis be affecting my memory?
Which medicines and substances can dull memory after a brain injury, and what to ask
Imagine a 52 year old woman two months after a crash. Her neck pain keeps her awake, so she takes the muscle relaxer from urgent care, a nighttime pain reliever from the drugstore, and sometimes a glass of wine to unwind. Her mornings feel foggy. She blames the concussion.
The concussion may be part of it. But the mix in her medicine cabinet could be adding to the fog. Many medicines and substances can affect attention and memory. The effects can be easy to miss because they build slowly or blend in with injury symptoms [1].
This article looks at which medicines and substances most often cloud thinking, why a brain injury can raise the risk, and how to get a safe review. It is general information. Your prescriber and pharmacist know your full health picture.
How medicines can cloud your thinking
Several groups of medicines can affect memory. The MSD Manual, a widely used medical reference, lists medicines with anticholinergic effects [1]. This group includes some antidepressants and many antihistamines [1]. Antihistamines are found in many over the counter sleep aids, cold remedies and allergy products [2]. Sleep medicines (sedatives) and opioid pain medicines are also on the list [1, 2].
Anticholinergic medicines block one of the chemical signals the nervous system uses. Older antihistamines with strong anticholinergic effects can cause confusion, dry mouth and constipation [3]. A Harvard Health guide adds tranquilizers, antidepressants and some blood pressure drugs to the medicines that can affect memory [4].
Clues that a medicine may be involved
Timing can offer a clue. Memory trouble linked to a medicine often begins after you start something new or take a higher dose [2]. It can also start after a health change, such as kidney or liver trouble, that slows how the body clears a medicine [2].
Write down when the fog started and what changed around that time. That note can help your prescriber sort out whether a medicine is part of the problem.
Comparison compiled by Safety Behind the Wheel Foundation
Common medicine groups that can affect thinking
| Medicine group | Often used for | Possible effect on thinking | A question to ask |
|---|---|---|---|
| Older, sedating antihistamines | Night sleep aids, cold and allergy products | Drowsiness, confusion | Is there a non sedating option? |
| Benzodiazepines and other sleep medicines | Sleep, anxiety | Slowed thinking, memory trouble, falls | Could I try sleep treatment without pills first? |
| Opioid pain medicines | Pain after injury or surgery | Drowsiness, memory trouble | How long should I take this? |
| Muscle relaxers | Neck and back strain | Fatigue, poorly tolerated by older adults | Do I still need this? |
| Some antidepressants | Depression, pain, sleep | Low energy, slower thinking with more sedating types | Is a less sedating choice possible? |
Sources: MSD Manual [1, 2]; VA/DoD guideline [5]; Living Concussion Guidelines [6]; AGS Beers Criteria 2023 [3, 7]; TBI Model Systems fatigue factsheet [8].
Why a brain injury can raise the risk
After a mild TBI, some people react more strongly to side effects, according to the 2021 VA/DoD guideline for veterans and service members [5]. The guideline tells prescribers to watch for harmful effects and drug interactions, and to check often for side effects [5]. It advises avoiding medicines that can cause confusion, such as benzodiazepines and anticholinergic drugs, and medicines that make seizures more likely [5].
Sleep medicines get extra caution. The VA/DoD guideline calls treatment without pills the first choice for long term insomnia [5]. It says that using medicine for sleep after a mild TBI can be complex. It asks prescribers to weigh risks such as toxicity and misuse [5]. For dizziness after mild TBI, it discourages some common benzodiazepines because they are sedating and habit forming [5]. A TBI Model Systems factsheet warns that many sleep drugs can be risky for people with TBI [9]. If you have used one for more than a week or two, it suggests talking with your doctor [9].
The Living Concussion Guidelines agree. This Canadian guideline for adults is updated as new research comes out. It says some antidepressants can worsen the low energy and thinking problems that come from the concussion itself [6]. The risk is greatest with the more sedating ones and those with stronger anticholinergic effects [6]. The guideline advises using mental health medicines with caution and choosing options without medicine where possible [6]. When medicines are used, it recommends starting at the lowest dose that works, raising it slowly, and changing only one medicine at a time [6].
Pain medicines and muscle relaxers
Pain after a crash is real, and treating it matters. Still, most pain medicines do not help much with long lasting pain. Many can be habit forming [10]. Muscle relaxers and pain medicines are also common sources of fatigue after TBI [8]. Fatigue itself makes memory slip.
These medicines can still be the right choice for some people, since pain that is not treated can also get in the way of memory and focus [9]. Ask your prescriber how long to take them and when to check back about side effects.
When medicines add up
Many people leave the hospital or urgent care with several new prescriptions, then add over the counter products at home. Each one may seem harmless. But medicines that act on the brain can stack their effects.
Picture a driver who leaves urgent care with a muscle relaxer and a pain pill. At home he adds a nighttime cold medicine to help him sleep. He already takes a pill for anxiety from before the crash. Each one alone might be fine. Taken together, several of them can cause drowsiness. Those effects can add up. Some of his foggy mornings may come from that mix. The VA/DoD guideline lists polypharmacy, which means taking many medicines at once, among the causes to rule out before treating dizziness after mild TBI [5].
What the Beers Criteria say for older adults
The American Geriatrics Society Beers Criteria list medicines that are often a poor fit for adults 65 and older [7]. The 2023 edition says all benzodiazepines raise the risk of thinking problems, delirium (sudden severe confusion), falls, fractures and car crashes in older adults [3]. It says the “Z drug” sleep medicines have much the same side effects [3]. It also says muscle relaxers used for aches and strains are poorly tolerated by older adults [3].
The criteria advise older adults not to take three or more brain acting medicines at once, because the mix raises the risk of falls and broken bones [3]. The groups that count include seizure medicines, antidepressants, antipsychotics, opioids, benzodiazepines and Z drugs [3]. The 2023 update added muscle relaxers to that list [7]. It also stressed the risks of taking several anticholinergic medicines together, and of combining benzodiazepines with opioids [7]. That pairing raises the risk of overdose [3]. For people with dementia or other thinking problems, the criteria advise avoiding anticholinergic drugs, benzodiazepines and Z drugs because of their effects on the brain [3].
The Beers Criteria were written for adults 65 and older, so they do not apply directly to younger people. Their warnings line up closely with the VA/DoD advice for adults with mild TBI [5].
Alcohol after a brain injury
Alcohol hits harder after a TBI. Many people become more sensitive to it after their injury [11]. Alcohol and brain injury both affect memory and flexible thinking, and the thinking effects of alcohol can last days to weeks after drinking stops [11]. Heavy drinking can disrupt short term memory even after you no longer feel its effects [4].
The risks go beyond memory. A TBI Model Systems factsheet says drinking after a TBI can bring on seizures and can slow or even halt recovery [11]. It also raises the chance of another injury. It can cause or deepen depression [11]. Alcohol also makes fatigue worse [8].
Mixing alcohol with medicines adds danger. Alcohol can make antidepressants work less well. It can boost the effects of some medicines enough to cause an overdose or death [11]. Drinking while taking medicine for anxiety or pain is especially risky [11]. The VA/DoD guideline asks providers to teach patients and families to avoid alcohol and other drugs while taking medicines [5].
How common drinking is after TBI
Up to half of adults with TBI drank more than the recommended amount before they were injured [11]. By two years after the injury, more than 40% have started drinking again [11]. For these reasons, brain injury doctors advise people with TBI to avoid alcohol completely [11]. Staying sober gives the brain its best chance to heal [11].
If cutting back is hard, help is available. Talk with your doctor about your drinking [11]. Counselors or psychologists in a brain injury rehabilitation program can help you find the right treatment. Some people find support groups useful [11]. Most people who quit alcohol or drugs do it on their own [11].
Cannabis and memory
In 2017, the National Academies of Sciences, Engineering, and Medicine reviewed more than 10,000 research summaries on cannabis [12]. The committee concluded that cannabis harms learning, memory and attention in the hours right after use [12]. There was limited evidence that some problems with learning, memory and attention may linger after people stop using it [12].
The report also found evidence that using cannabis before driving raises the risk of a crash [12]. It linked cannabis use to a higher risk of psychosis and social anxiety, and to a smaller extent depression [12]. On the other side, the committee found that cannabis and related products can reduce chronic pain in some adults [12].
The report did not focus on people with brain injuries. A 2021 TBI Model Systems factsheet says even occasional cannabis use may cause thinking problems that last at least a day [11]. It concludes that, for now, the risks of cannabis for people recovering from a TBI seem to outweigh the benefits [11]. Marijuana also tends to make fatigue worse [8].
Cannabis laws differ from state to state. A product being legal where you live does not make it safe to use before driving.
Getting a safe medicine review
Do not stop or change a prescribed medicine on your own. Some medicines need to be adjusted slowly. Your prescriber can tell you how to do it safely. When a medicine is suspected, a doctor may stop it or swap it on purpose to see whether memory improves [2]. Changing one medicine at a time makes it easier to tell what helped [6].
When you ask about memory, your provider should go over every medicine and supplement you take, including over the counter products [1]. The Living Concussion Guidelines recommend a thorough medicine review when fatigue is a problem, and switching to an option that does the same job without causing tiredness when possible [13]. A pharmacist can also check your full list for overlap and interactions. Speak up if you think a new medicine is taking the edge off your memory [4].
Checklist from Safety Behind the Wheel Foundation
- Gather every pill bottle, patch, inhaler and supplement you use, including sleep aids and allergy pills.
- Write down the dose, the time you take each one, and who prescribed it.
- Note when your memory or focus seemed to change, and any new medicine or dose around that time.
- Show the list or the bottles to a pharmacist or to the person who prescribes for you, and request a full review [1, 4].
- Ask whether any medicine has sedating or anticholinergic effects [1, 5].
- Be honest about alcohol and cannabis use so your care team can spot risky mixes [11].
- Watch for side effects that may affect your thinking, and report them early [14].
A word about driving
Several of these medicines and substances can impair driving. In older adults, benzodiazepines are linked to more motor vehicle crashes [3]. Cannabis before driving raises crash risk [12]. After a TBI, alcohol is most risky for tasks that need balance and quick reactions. Driving is one of them [11]. If you start a new medicine that makes you sleepy or foggy, ask your prescriber whether it is safe to drive. Driving rules for people with brain injuries differ from state to state.
Get emergency help
Mixing alcohol with sedating medicines can lead to overdose [11]. Call 911 right away if someone, especially after a head injury, shows any of these signs [15]:
- Is extremely sleepy, passes out, or cannot be roused.
- Seems confused, restless or agitated, or does not know familiar people or places.
- Has slurred speech or acts strangely.
- Has weakness, numbness, clumsiness, convulsions or seizures.
- Vomits several times.
- Has a headache that keeps building.
- Has pupils of different sizes.
If someone feels depressed and is thinking of self harm, get help at once by calling 988 or 911 [1].
Questions to ask your care team
Question checklist from Safety Behind the Wheel Foundation
- Could any of my medicines or supplements be affecting my memory or focus?
- Do any of my medicines have sedating or anticholinergic effects?
- Am I taking more than one medicine that acts on the brain, and can any be reduced?
- Is there a sleep treatment I can try that does not involve pills?
- How long should I keep taking this pain medicine or muscle relaxer?
- If we change a medicine, how should we do it, and what should I watch for?
- Is it safe for me to drink any alcohol with my medicines and my injury?
- Could cannabis interfere with my recovery or my medicines?
- Can I drive safely on these medicines?
Frequently asked questions
Should I stop my sleeping pill if my memory is bad?
Not on your own. Talk with your prescriber first. The VA/DoD guideline calls treatment without medicine the first choice for long term insomnia [5], so your prescriber may help you shift toward that approach and adjust the medicine safely.
Is an occasional drink safe after a concussion?
Brain injury guidance urges people with TBI not to drink at all, because alcohol can trigger seizures, slow recovery and affect memory for days to weeks [11]. If you choose to drink, talk with your care team first, especially if you take any medicines [11].
Is medical cannabis a safer choice?
The National Academies found some evidence that cannabis can ease chronic pain in adults [12]. For people recovering from a TBI, the TBI Model Systems say the risks currently seem to outweigh the benefits [11]. Cannabis also impairs memory and attention right after use, whether it is medical or not [12].
Will my memory improve if a medicine is changed?
It may. Doctors sometimes stop or switch a suspected medicine to see whether memory gets better [2]. Results vary. The brain injury itself may still cause some symptoms, so keep notes and follow up with your care team.
The bottom line
Recommendation from Safety Behind the Wheel Foundation
Medicines, alcohol and cannabis can each add fog on top of a brain injury. Sedating sleep aids, older allergy pills, some pain and anxiety medicines and muscle relaxers are common culprits. The risk grows when several are taken together.
Bring a full list of everything you take to your prescriber or pharmacist, make changes one at a time under their guidance, and avoid alcohol and cannabis while you recover. Those steps can remove a cause of memory trouble that is easy to fix.
Sources and further reading
- 1Freedman M. Memory loss. MSD Manual Consumer Version. Updated January 2026. msdmanuals.com/…/memory-loss
- 2MSD Manual Consumer Version. Table: some causes and features of memory loss. 2026. msdmanuals.com/…/some-causes-and-features-of…
- 32023 American Geriatrics Society Beers Criteria Update Expert Panel. American Geriatrics Society 2023 updated AGS Beers Criteria for potentially inappropriate medication use in older adults. Journal of the American Geriatrics Society. 2023;71(7):2052-2081. doi.org/10.1111/jgs.18372
- 4Pendick D. 7 common causes of forgetfulness. Harvard Health Publishing. Updated April 2020. health.harvard.edu/…/7-common-causes-of-forgetfu…
- 5U.S. Department of Veterans Affairs, U.S. Department of Defense. VA/DoD clinical practice guideline for the management and rehabilitation of post-acute mild traumatic brain injury: provider summary. Version 3.0. 2021. healthquality.va.gov/…/VADoDmTBICPGProviderSummary…
- 6Living Concussion Guidelines. Section 8: Mental health disorders (adult guideline). Ottawa Hospital Research Institute. Updated April 2023. concussionsontario.org/…/mental-health-disorders
- 7Adebogun O, Phillips J. A summary of the 2023 American Geriatrics Society updated Beers Criteria for potentially inappropriate medication use in the elderly. University of Illinois Chicago College of Pharmacy, Drug Information Group. September 2023. dig.pharmacy.uic.edu/…/a-summary-of-the-2023-ameri…
- 8Model Systems Knowledge Translation Center. Fatigue and traumatic brain injury. Updated 2024. msktc.org/…/fatigue-and-traumatic-brain…
- 9Model Systems Knowledge Translation Center. Chronic pain after traumatic brain injury (TBI): part 1. 2020. msktc.org/…/traumatic-brain-injury-and-…
- 10Model Systems Knowledge Translation Center. Chronic pain after TBI: part 2. 2020. msktc.org/…/traumatic-brain-injury-and-…
- 11Bombardier CH, Corrigan JD. Alcohol use after traumatic brain injury. Model Systems Knowledge Translation Center. 2021. msktc.org/…/alcohol-use-after-traumatic…
- 12National Academies of Sciences, Engineering, and Medicine. Health effects of marijuana and cannabis derived products presented in new report. January 2017. nationalacademies.org/…/health-effects-of-marijuana…
- 13Living Concussion Guidelines. Section 11: Fatigue (adult guideline). Ottawa Hospital Research Institute. Updated May 2023. concussionsontario.org/…/fatigue
- 14Model Systems Knowledge Translation Center. Cognitive problems after traumatic brain injury. 2020. msktc.org/…/cognitive-problems-after-tr…
- 15Centers for Disease Control and Prevention. Symptoms of mild TBI and concussion. Last reviewed September 2025. cdc.gov/…/index.html
This article reflects the safety priorities of brain injury recovery and impaired driving prevention. It is general education and does not replace medical or pharmacy advice. Check official sources and talk with your own care team, including whoever prescribes your medicines, before starting, stopping or changing any of them. Reviewed October 2026.
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