- Alzheimer's disease - the most common cause of dementia (65% of dementias are due to Alzheimer's Disease). It is more common in older people and gradually appears rather than suddenly. People with Alzheimer's may experience mild hallucinations, may have unusual sleep patterns and often seem unaware of any problems.
- Vascular Dementia - this is more abrubt that Alzheimers and is linked to strokes and atheroschlerosis (both of which can cause infarcts - blocked arteries resulting in a lack of oxygen to the brain). Unlike Alzheimer's disease, the patient's personality doesn't seem to be affected as much. Vascular dementia often seems to occur at the same time as Alzheimer's disease, making diagnosis difficult and confusing.
- Dementia with Lewy Body (DLB) - commonly indicated by strong visual hallucinations and apparent periods of relative "normality" contrasting with periods of dementia. This may be accompanied by fainting and loss of consciousness and symptoms similar to Parkinson's disease (tremor and rigidity)
- Fronto-Temporal Dementia (FTD) - including Pick's disease, this has an earlier onset than Alzheimer's (often between the ages of 50-60) and appears to be partly genetic, often running in families. People with FTD are often impulsive, lack inhibitions, and can sometimes show strange or innapropriate behaviour (such as imitating others).
- Other causes - chronic alchohol abuse (Korsakoff syndrome) - HIV - CJD (the rare disease originally thought to be related to BSE infected beef) - toxic substances - brain tumours - head injuries and brain damage.