Reversible dementias account for less than 20% of the number of dementia cases. Although the causes listed above tend to be reversible, occasionally the dementia will not reverse following treatment. The reversibility of the dementia depends upon; the causative condition, duration to the illness, severity of the illness, and other coexisting illnesses.

The most common causes of reversible dementia include depression, alcohol abuse, and drug toxicity. Less common causes of reversible dementia include normal-pressure hydrocephalus, neoplasm, metabolic disorders (i.e.. hypothyroidism), trauma, and infection.