Experts have found more evidence that prescribing dementia patients "chemical cosh" drugs increases their risk of early death.
Antipsychotics are widely used in care homes and hospitals, but critics argue they are often given to sedate patients to make them easier to look after rather than for any medical benefit.
Guidelines say they should only be used as a last resort and over a short period of time, but in some cases patients have been prescribed them for years.
The latest research from Harvard Medical School is the biggest ever among US nursing home residents, involving 75,445 people aged 65 and over.
It examined a range of drugs and found one in particular - haloperidol -increased the risk a patient would die.
Haloperidol is widely used in the UK as well as the US.
Compared with the drug risperidone, users of haloperidol had double the risk of death, while those on another drug, quetiapine, had a decreased risk, the study found.
Writing online in the British Medical Journal, the experts 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."
They suggest not all antipsychotic medication carries the same risk of death but that doctors may want to consider the evidence when prescribing the drugs.
Previous studies have found that antipsychotics as a class of drugs double the risk of death and treble the risk of stroke in dementia patients.
A Government-commissioned review in 2009 found 180,000 people with dementia were prescribed antipsychotics, of which 144,000 were given them inappropriately.
The drugs have been dubbed a "chemical cosh" due to their effects and are thought to contribute to the premature deaths of 1,800 patients a year.
Rebecca Wood, chief executive at Alzheimer's Research UK, said: "The risks associated with antipsychotics are well-established, and these findings underline the importance of ensuring that where these drugs are prescribed, their use must be carefully monitored.
"Antipsychotics should only be used for people with dementia where there is no alternative for dealing with challenging behaviour.
"Alzheimer's Research UK has called for action to reduce the use of antipsychotics and develop alternatives, yet progress has been frustratingly slow.
"While we welcome research that can inform doctors' decisions about prescribing existing medication, we urgently need to find safer, more effective treatments for people with dementia.
"These can only come through research, but funding for dementia research still lags far behind that of other serious diseases. If we are to improve the lives of people with dementia, we must invest in research."
Dr Anne Corbett, research manager at the Alzheimer's Society, said: "This research supports existing studies that have shown antipsychotics can raise the risk of death, particularly when used over the longer term.
"For a minority of people with dementia antipsychotics should be used, but then only for up to 12 weeks and under the correct circumstances.
"For the majority, they do far more harm than good.
"It is essential alternative treatment approaches are provided to help GPs and other medical professionals reduce the prescribing of these dangerous drugs."
A spokesman for the Department of Health said reducing the level of antipsychotics prescribing for people with dementia by two-thirds is one of the key priorities in the National Dementia Strategy.
"The national audit of anti-psychotics prescribing will report its findings on progress on this later this year."