Memory loss can be caused by anything that disrupts normal functioning of the brain. This is usually due to disease or head injury. Conditions that may cause memory loss include:

• Alzheimer's disease, dementia. A disease of the brain that gets worse over time. It is the most common cause of dementia among people over the age of 65, according to the National Institute of Neurological Disorders and Stroke. Both conditions involve the death of neurons (nerve cells) in the brain or loss of their ability to connect with other neurons. When this affects neurons or parts of the brain associated with memory, memory loss can occur. Anterograde amnesia is one of the first symptoms of Alzheimer's disease. As the disease progresses, patients may also permanently lose long-term memory, become unable to understand language, and may even forget how to swallow.
  
  
• Head injury. Physical injury to the head may include damage to parts of the brain that affect memory. Head injuries can have a variety of causes, including car accidents, falls, sports mishaps and brain surgery. People with head injuries often experience memory loss of events immediately preceding the injury (retrograde amnesia). Sometimes these memories are never recovered. People with severe brain injuries may experience permanent memory loss and have trouble forming memories for the rest of their life. Head injuries rarely result in memory loss that gets progressively worse (as is seen in certain degenerative neurological conditions, such as dementia).
  
  
• Epilepsy. Epilepsy is a neurological disorder that involves a tendency to experience disruption of electrical activity in the brain that causes recurring seizures. Epilepsy may be caused by brain injury, certain medical conditions (e.g., cerebral palsy) or genetics, although in many cases the cause is unknown. People with epilepsy may experience damage or disruption of brain functioning that can result in memory loss. This is especially true for people who have seizures that affect the temporal lobe, which is thought to be critical for memory storage.
  
  
• Parkinson’s disease. Parkinson’s disease is chronic, progressive disease in which patients lose brain cells that produce the neurotransmitter dopamine, which helps to regulate movement. As a result, it causes several characteristic symptoms, including tremors, slowness of movement and rigidity. It can also cause memory loss.
  
  
• Substance abuse. Alcohol is believed to damage the hippocampus, a brain structure involved with memory storage. Even relatively minor alcohol intake can cause memory loss to a certain extent. People who drink large quantities of alcohol over a long period of time can develop a condition called Wernicke-Korsakoff syndrome. This syndrome is caused by a lack of thiamine – a common vitamin deficiency in alcoholics – and may cause permanent memory loss. In addition, the abuse of certain drugs, (e.g., barbiturates, hallucinogens), can alter brain chemicals and make it more difficult for a person to recall memories.
  
  
• Stroke. A stroke is a life-threatening event in which part of the brain is deprived of adequate oxygen (hypoxia). Also known as a cerebrovascular accident (CVA) or a “brain attack,” a stroke occurs when a blood vessel in the brain bursts or becomes clogged by a blood clot or other mass. This prevents oxygen and nutrients from getting to nerve cells in the affected area of the brain. These nerve cells can die within minutes, and the area of the body that they control can cease to function. In many cases, this damage is permanent, especially if the patient is not treated immediately.
  

  

• Brain tumors or lesions. Tumors or brain lesions, which can cause pressure to build in the brain, can disrupt the function of neurons, leading to memory loss. In some cases, removal of the tumor or lesion may restore memory function, although sometimes the memory loss may be permanent.
  
  
• Side effects of certain medications. Some medications, particularly sedatives such as benzodiazepines and anticholinergics, may cause temporary memory loss.
  
  
• Psychological trauma. Severe emotional distress can cause psychogenic amnesia, a type of memory loss that is psychological in origin (no brain injury or damage is present).  

Many additional conditions can cause memory loss. This includes certain infections (e.g., encephalitis, meningitis, syphilis, HIV), degenerative diseases (e.g., Huntington’s disease) and brain disorders (e.g., Creutzfeldt-Jakob disease). Additional causes of memory loss may include malnutrition and exposure to toxins.