Why Do We Forget Things? Causes of Memory Loss

Causes of Memory Loss

Don't Forget!. Sharon Dominick E+/ Getty Images

Most of us have, either occasionally or more frequently, had the unpleasant experience of forgetting something. Forgetfulness results in a range of consequences, such as a poor grade when a university student forgets he has an exam in class that day, to a missed meeting at work, to much more significant concerns — including becoming lost on your way home or not remembering your daughter's name.

So what causes us to forget?

Turns out, there are many possibilities. Here are some of the many reasons we can't remember:

  • Stress

    Too much stress can overload our minds and cause distraction and brain drain.

  • Distraction

    Thinking about too many things at once? Attempts to multi-task in order to be efficient can actually decrease efficiency because of the need to repeat a task that was poorly completed or forgotten. Your brain has a limit on what it can effectively process simultaneously and remember.

  • Fatigue

    The benefits of getting a good night's sleep are many: less weight gain, more energy, and the ability to think more clearly.

  • Poor Memory

    No offense here, but there are some people who just don't have a great memory. Maybe you've seen the differences of one person who needs to spend three hours to effectively learn and remember material, and another who has it mastered and can quickly recall it after taking only 20 minutes to page through it.

  • Depression

    Depression can blunt the mind and cause such disinterest in your surroundings that memory and orientation appear to suffer. Pseudodementia is a term that describes this condition; testing will indicate normal cognitive functioning, despite the feeling that the brain is disengaged and not functioning well.

  • Anxiety

    If you've ever blanked out when taking a test even though you knew the information, you can blame anxiety. Some people have anxiety in certain situations, like the test-taking example, and others have a more pervasive generalized anxiety disorder that continually interferes with healthy functioning, including the ability to remember.

  • Grief

    Grieving requires physical and emotional energy, and can reduce our ability to focus on events and people around us. Consequently, our memory can suffer because we may not have been tuned in.

  • Alcohol or Illicit Drugs

    Binging on alcohol or using illicit drugs can impair memory, both in the short-term and long-term. From blackouts on the same day to an increased risk of dementia years later, these substances can definitely harm your memory, among many other things.

  • Prescription Medications

    Even though they may be prescribed by a physician, if you combine too many drugs or take them incorrectly, prescription medicines can significantly affect your ability to remember clearly.

  • Chemotherapy

    If you're receiving chemotherapy as a treatment for cancer, you might experience "chemo-brain", described by people as brain fog from the medicines targeting your cancer.

  • Head Injuries

    Concussions and traumatic head injuries can cause short-term memory impairment, but also increase the likelihood for the development of dementia over the years.

  • Heart Surgery

    Some research has indicated that following bypass surgery, people are more likely to experience bouts of confusion and short-term memory impairment.

  • Anesthesia

    Some people report memory loss or confusion, typically lasting for a few days, following the use of anesthesia. Research, however, has been unclear in determining if there's a direct correlation between the anesthesia or if other factors may be causing the brain to function less effectively.

  • Electroconvulsive Therapy

    Sometimes referred to as "shock" therapy, ECT can be very helpful for those suffering from severe depression, but it may also cause some memory loss.

  • Low Vitamin B12

    Vitamin B12 is a very important vitamin. In the more extreme cases, deficits in vitamin B12 have caused symptoms that have been mistaken for dementia. Upon receiving adequate vitamin B12, those symptoms may improve.

  • Aging

    As people age into older adulthood, cognitive processing generally slows down, and memory may slightly decline. For example, a healthy older person will still be able to memorize information, but it probably won't be as easy as when he was a child or young adult.

  • Thyroid, kidney or liver disorders

    Physical impairments in these organs can affect cognitive functioning, including your memory.

  • Encephalitis

    This infection in the lining of the brain may trigger symptoms of dementia.

  • Infections

    Infections such as pneumonia or urinary tract infections can cause forgetfulness, especially in older adults and others with chronic health conditions. Prompt treatment, usually with an antibiotic, can often help restore memory to its normal functioning.

  • Transient Ischemic Attacks

    TIAs, also known as "little strokes" (although that isn't completely accurate medically), is a brief blockage in the brain that can cause lapses in memory, along with other stroke-like symptoms.

  • Delirium

    Delirium, a sudden change in responsiveness and thinking ability, can be caused by infections, as noted above — but by several other conditions as well. Deliriums are serious but typically respond well to treatment, and are generally reversible.

  • Mild Cognitive Impairment

    One symptom of mild cognitive impairment is forgetfulness. MCI may respond to medications that are designed to treat Alzheimer's.

  • Alzheimer's Disease

    Alzheimer's is the most common cause of dementia and causes significant, not just inconvenient, memory loss in addition to multiple other symptoms. If you think your memory loss could be caused by Alzheimer's, review the symptoms and make an appointment with your physician for an assessment. Keep in mind that, although Alzheimer's typically affects those over the age of 65, early onset Alzheimer's can infrequently occur in those as young as 40.

  • Other Dementia

    Memory loss can also be caused by other kinds of dementia, such as vascular dementia, Lewy body dementia, frontotemporal dementia and several others.

Resources for Memory Maintenance and Improvement


Anesthesia and Analgesia. 2005;101:916–9. Transient Global Amnesia After General Anesthesia. http://www.anesthesia-analgesia.org/content/101/3/916.full.pdf

Brain Institute. Oregon Health & Science University. Causes of Memory Loss and Other Related Problems. Accessed March 21, 2013. http://www.ohsu.edu/xd/health/services/brain/getting-treatment/diagnosis/alzheimers-aging/about/causes-of-memory-loss.cfm

The Harvard Medical School Family Health Guide. Bypass surgery and memory. http://www.health.harvard.edu/fhg/updates/update0206c.shtml

National Institutes of Health. National Institute on Aging. Forgetfulness: Knowing When To Ask For Help. Accessed March 21, 2013. http://www.nia.nih.gov/health/publication/forgetfulness-knowing-when-ask-help

U.S. Food and Drug Administration. Coping With Memory Loss. Accessed March 21, 2013. http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm107783.htm

U.S. National Library of Medicine. National Institutes of Health. Memory Loss. Accessed March 21, 2013. http://www.nlm.nih.gov/medlineplus/ency/article/003257.htm

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