People taking antipsychotic drugs are nearly twice as likely to have a stroke as those not on the treatment. The risk is even higher -- about 3.5 times -- for men and women with dementia.

Researchers looked at the medical records of nearly 7,000 men and women, and recorded the incidence of stroke among those who had at some point taken antipsychotic drugs. The increased risk applied both to older drugs, such as phenothiazines, haloperidol and benperidol, and newer drugs such as Risperdal, Zyprexa, Solian and Seroquel.

The researchers did not look at why people with dementia are at greater risk. It may be related to the vascular causes of certain types of dementia.