London: Researchers have claimed that some anti-psychotic drugs may actually be harmful for dementia patients as these could raise their death risk.

The drugs have a powerful sedative effect so are often used when dementia patients become aggressive or distressed.

Now, a new research, led by Harvard Medical School, has claimed that anti-psychotics shouldn't be used "in the absence of clear need", the British Medical Journal' reported.

In their research, the researchers analysed 75,445 people in hospitals who had dementia and prescribed anti-psychotics.

The researchers said some drugs were associated with more than twice the risk of death than risperidone, another anti-psychotic which was used as a benchmark to compare the other drugs.

The study concluded: "The data suggest that the risk of mortality with these drugs is generally increased with higher doses and seems to be highest for haloperidol and least for quetiapine."

The Dementia Action Alliance -- which includes the Alzheimer's Society, Age UK and the Department of Health -- has called for all prescriptions for anti-psychotics to be reviewed by the end of March 2012.

Dr Chris Fox, who researches dementia at the University of East Anglia, was quoted by the 'BBC' as saying, "This study provides an interesting insight into the differential harm of these medicines.

"More work is needed on alternatives to these medicines in dementia with behavioural problems. In addition, there is a need to consider duration of use in more acute situations such as severe distress."