Memory loss causes can range from everyday problems such as stress and poor sleep to medication side effects, nutritional deficiencies and medical conditions.
Forgetting something occasionally does not necessarily mean that a person has dementia. Mild forgetfulness can be a normal part of aging, while more significant or worsening memory problems deserve medical attention.
According to the National Institute on Aging (NIA), memory problems may be associated with medical conditions, medications, mental health, sleep problems, nutritional deficiencies, alcohol or drug misuse and other factors.
Some of these causes may be treatable or reversible. For this reason, persistent or unexplained memory loss should be assessed rather than automatically assumed to be dementia.
Common Memory Loss Causes: 12 Reasons You May Be Forgetful
1. Stress
Periods of significant or ongoing stress can make it harder to concentrate, process information and remember things.
When your attention is divided by worry or emotional pressure, information may not be encoded into memory as effectively in the first place. This can make everyday forgetfulness more noticeable.
The NIA includes stressful life events and negative emotions among factors that may cause temporary memory problems. Stress-related forgetfulness may improve as the stressful situation and associated emotions ease.
Long-term stress may also affect sleep, mood and general health, which can further influence memory and concentration.
If memory problems continue after a stressful period has passed, it is worth discussing them with a healthcare professional.
2. Medications
Medication side effects are another possible cause of memory problems, particularly in older adults who take several medicines.
Some medications can contribute to confusion, drowsiness, reduced concentration or forgetfulness. The effect may also result from an interaction between different medicines rather than one drug alone.
The Mayo Clinic lists certain medicines and combinations of medicines among potentially reversible causes of memory loss.
If memory problems begin after starting or changing medication, speak with a doctor or pharmacist. Do not stop prescription medicines without medical advice.
It is also useful to keep an up-to-date list of all prescription medicines, over-the-counter products and supplements and share it with each healthcare professional you see.
3. Alcohol and Drug Misuse
Heavy alcohol use can interfere with the brain’s ability to form and retrieve memories.
Alcohol can produce short-term memory gaps or blackouts after heavy drinking. Prolonged excessive alcohol use can also contribute to nutritional deficiencies and alcohol-related brain damage.
In particular, severe thiamine, or vitamin B1, deficiency associated with chronic alcohol misuse can lead to serious neurological conditions such as Wernicke-Korsakoff syndrome.
Alcohol and drug misuse are included by the NIA among factors that can contribute to memory problems.
Our article on alcohol and dementia looks more closely at how long-term alcohol consumption can affect the brain.
4. Vitamin B12 and Other Nutritional Deficiencies
The brain and nervous system depend on an adequate supply of nutrients to function normally.
Low vitamin B12 is particularly important because deficiency can cause neurological and cognitive symptoms, including confusion and memory problems.
The NIA identifies low levels of important nutrients such as vitamin B12 as one of the possible memory loss causes that should be considered.
Vitamin B12 occurs naturally in foods such as:
- Fish and seafood
- Meat
- Eggs
- Milk and other dairy products
- Foods fortified with vitamin B12
However, a person can develop B12 deficiency even when their diet appears adequate because some medical conditions and medications affect absorption.
A doctor can investigate possible deficiency with appropriate tests. Read more in our guide to vitamin B12 and dementia.
5. Traumatic Brain Injury
A concussion or more serious traumatic brain injury (TBI) can affect memory, attention and the ability to learn new information.
Memory loss around the time of an injury is common. Some people have difficulty remembering events immediately before or after the injury, while others experience longer-lasting cognitive problems.
The severity and duration of memory symptoms vary considerably depending on the location and extent of the injury.
Even a relatively minor head injury can sometimes cause memory problems, which is why a noticeable change following a fall or accident should be medically assessed.
See our detailed article on dementia and traumatic brain injury for more information.
6. Depression, Anxiety and Grief
Memory is closely connected with attention and concentration. Depression, anxiety, grief and major emotional events can therefore make a person feel unusually forgetful.
Someone coping with bereavement, for example, may have difficulty concentrating on conversations or remembering everyday information because so much mental and emotional energy is directed toward the loss.
Depression and anxiety can also interfere with sleep and motivation, further affecting cognitive performance.
The NIA identifies depression and anxiety, along with major stressful or traumatic life events, among factors that may contribute to memory problems.
Memory symptoms associated with emotional distress can sometimes improve as the underlying condition improves. Persistent symptoms should still be discussed with a healthcare professional.
People coping with bereavement may also find our information on coping after the death of someone with dementia helpful.
7. Smoking and Vascular Health
Smoking is better understood as a risk factor for poor cardiovascular and brain health than as an immediate cause of ordinary forgetfulness.
Smoking damages blood vessels and increases the risk of cardiovascular disease and stroke. Healthy blood flow is important because the brain requires a constant supply of oxygen and nutrients.
Over time, vascular damage can contribute to cognitive impairment and increase the risk of vascular dementia and other forms of dementia.
Stopping smoking benefits both cardiovascular and brain health. Our article on smoking and dementia examines this relationship in more detail.
8. Mild Cognitive Impairment (MCI)
Mild cognitive impairment, or MCI, describes memory or thinking difficulties that are greater than expected for a person’s age but are not severe enough to prevent most normal everyday activities.
Signs may include:
- Losing things more often
- Forgetting appointments or important events
- Having more difficulty finding words
- Noticing increasing problems with memory or thinking
MCI is not the same as dementia.
Some people with MCI remain stable or even improve, while others eventually develop Alzheimer’s disease or another form of dementia. There is no single cause of MCI, so medical assessment is important.
9. Sleep Problems
Sleep plays an important role in attention, learning and memory.
A poor night’s sleep can make it difficult to concentrate the following day. Repeated sleep deprivation can make these problems more noticeable.
Sleep disorders may also contribute. For example, obstructive sleep apnea repeatedly interrupts normal breathing during sleep and can affect daytime alertness and cognitive functioning.
The NIA includes sleep problems among possible causes of memory difficulties.
If someone regularly snores heavily, stops breathing during sleep, wakes repeatedly or remains very tired during the day despite spending enough time in bed, they should discuss these symptoms with a healthcare professional.
Read more about the relationship between sleep and dementia.
10. Stroke and Other Brain Conditions
Memory problems can sometimes result from conditions that directly affect the brain.
A stroke occurs when blood supply to part of the brain is interrupted or a blood vessel in the brain bursts. Depending on which areas are affected, a stroke can cause problems with memory, language, reasoning and other cognitive abilities.
Some small strokes produce relatively subtle symptoms and may only be discovered during medical investigation.
The NIA also notes that blood clots, brain tumors and infections can cause memory problems.
Sudden memory loss or confusion, particularly when accompanied by facial drooping, weakness, speech difficulty, severe headache or problems walking, requires urgent medical attention.
Learn more about stroke and dementia.
11. Underactive Thyroid (Hypothyroidism)
An underactive thyroid, also called hypothyroidism, occurs when the thyroid gland does not produce enough thyroid hormone.
Symptoms can include fatigue, feeling cold, weight changes, low mood, slowed thinking and difficulty concentrating. Some people also experience memory problems.
Because these symptoms can sometimes resemble aspects of cognitive decline, thyroid function is one of the medical issues a doctor may investigate when assessing unexplained memory changes.
Hypothyroidism can usually be detected with blood tests and treated when appropriate.
This is another reason not to assume that new memory problems automatically indicate Alzheimer’s disease or dementia.
12. Dementia and Alzheimer’s Disease
Persistent and progressively worsening memory loss can sometimes be caused by dementia.
Dementia is not one disease. It is a general term describing a decline in cognitive abilities severe enough to interfere with everyday life.
Alzheimer’s disease is the most common cause of dementia among older adults. Memory problems are often one of its earliest symptoms, although Alzheimer’s can also affect reasoning, language, judgment and behavior.
Other forms include vascular dementia, Lewy body dementia and frontotemporal dementia.
Importantly, dementia is not a normal or inevitable part of getting older. Many people remain cognitively healthy well into advanced age.
Normal Forgetfulness or Something More Serious?
Occasional forgetfulness happens to almost everyone.
The National Institute on Aging explains that normal age-related forgetfulness can include occasionally making a poor decision, forgetting which day it is and remembering later, or sometimes losing things.
More serious memory problems interfere with everyday life.
Examples that warrant medical attention can include:
- Asking the same questions repeatedly
- Getting lost in familiar places
- Having difficulty following familiar instructions or recipes
- Becoming increasingly confused about people, places or time
- Having difficulty managing normal daily activities
- Memory problems that are becoming noticeably worse
If you are concerned about your own memory or that of someone close to you, seeking an assessment can help identify the cause.
Why Identifying Memory Loss Causes Matters
There is no single explanation for memory loss.
Some memory loss causes, such as medication effects, nutritional deficiencies, thyroid problems, sleep difficulties or emotional conditions, may be treatable. Others, including Alzheimer’s disease and certain neurological conditions, require different forms of medical care and support.
A healthcare professional may review symptoms, medications and medical history and carry out physical, neurological, cognitive or laboratory tests where appropriate.
Getting an accurate diagnosis is far more useful than assuming that forgetfulness is simply aging or, at the other extreme, assuming that every memory lapse means dementia.
Closing Thoughts on Memory Loss Causes
Memory changes can happen for many reasons.
Stress, medication side effects, alcohol misuse, vitamin deficiencies, head injury, depression, poor sleep and thyroid problems are just some possibilities. Mild cognitive impairment, stroke and dementia can also affect memory.
The important point is that memory loss does not automatically mean dementia.
If memory problems are new, worsening, persistent or beginning to interfere with everyday life, speak with a doctor. Identifying the cause is the first step toward deciding what treatment, support or further investigation may be appropriate.
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