Dementia is the loss of mental functions such as thinking, memory, and reasoning that is severe enough to interfere with a person's daily functioning. Dementia is not a disease itself, but rather a group of symptoms that are caused by various diseases or conditions. Symptoms can also include changes in personality, mood, and behavior. In some cases, the dementia can be treated and cured because the cause is treatable. Examples of this include dementia caused by substance abuse (illicit drugs and alcohol), combinations of prescription medications, and hormone or vitamin imbalances. In some cases, although the person may appear to have dementia, a severe depression can be causing the symptoms. This is known as pseudo-dementia (false dementia) and is highly treatable. In most cases, however, true dementia cannot be cured.
Dementia develops when the parts of the brain that are involved with learning, memory, decision-making, and language are affected by one or more of a variety of infections or diseases. The most common cause of dementia is Alzheimer's disease, but there are as many as 50 other known causes. Most of these causes are very rare.
Because some causes of dementia can be cured or partially treated, it is very important that your doctor is thorough when making the diagnosis, so as not to miss potentially treatable conditions. The frequency of "treatable" causes of dementia is believed to be about 20%.