It's the stuff movies are made of. A person suffers a blow to the head and then wanders aimlessly, unable to remember who he is or where he came from. While such sudden, profound loss of memory is rare, memory loss is a problem that affects most people to a degree.Whether it's occasional forgetfulness or loss of short-term memory that interferes with daily life, there are many causes of memory loss.

• Causes of Memory Loss

Here are some of the more common things that can cause memory loss:

* Medications. A number of prescription and over-the-counter medications can interfere with or cause loss of memory. Possible culprits include: antidepressants, antihistamines, anti-anxiety medications, muscle relaxants, tranquilizers, sleeping pills, and painmedications given after surgery.

* Alcohol, tobacco, or drug use. Excessive alcohol use has long been recognized as a cause of memory loss. Smoking harms memory by reducing the amount of oxygen that gets to the brain. Studies have shown that people who smoke find it more difficult to put faces with names than do nonsmokers. Illicit drugs can change chemicals in the brain that can make it hard to recall memories.

* Sleep deprivation Both quantity and quality of sleep are important to memory. Getting too little sleep or waking frequently in the night can lead to fatigue, which interferes with the ability to consolidate and retrieve information.

* Depression and stress. Being depressed can make it difficult to pay attention and focus, which can affect memory. Stress and anxiety can also get in the way of concentration. When you are tense and your mind is overstimulated or distracted, your ability to remember can suffer. Stress caused by an emotional trauma can also lead to memory loss.

* Nutritional deficiency. Good nutrition -- including high-quality proteins and fats -- is important to proper brain function. Deficiencies in vitamin B1 and B12 specifically can affect memory.

* Head injury. A severe hit to the head -- from a fall or automobile accident, for example -- can injure the brain and cause both short- and long-term memory loss. Memory may gradually improve over time.

* Stroke. A stroke occurs when the blood supply to the brain is stopped due to the blockage of a blood vessel to the brain or leakage of a vessel into the brain. Strokes often cause short-term memory loss. A person who has had a stroke may have vivid memories of childhood events but be unable to recall what he or she had for lunch.

* Dementia. Dementia is the name for progressive loss of memory and other aspects of thinking that are severe enough to interfere with the ability to function in daily activities. Although there are many causes of dementia -- including blood vessel disease, drug or alcohol abuse, or other causes of damage to the brain -- the most common and familiar is Alzheimer's disease. Alzheimer's disease is characterized by a progressive loss of brain cells and other irregularities of the brain.

* Other causes. Other possible causes of memory loss include an underactive or overactive thyroid gland and infections such as HIV, tuberculosis, and syphilis that affect the brain

If you find yourself being increasingly forgetful or if memory problems interfere with your daily life, schedule an appointment with your doctor to determine the cause and best treatment.To evaluate memory loss, your doctor will take a medical history, perform aphysical exam -- including a neurologic exam -- and ask questions to test mental ability. Depending on the results, further evaluation may include blood and urine tests, nerve tests, and imaging tests of the brain such as computerized axial tomography (CAT) scans or magnetic resonance imaging (MRI).