Sedatives and sleeping pills prescribed to ease depression, anxiety and sleep problems appear to increase the risk of suicide four-fold among the elderly, Swedish researchers said on Wednesday.

A review of elderly Suicides in the Swedish city of Gothenburg and two nearby counties showed that antidepressants, antipsychotics, sedatives and hypnotics appeared to make it more likely an older person would commit suicide.

While research has linked use of these drugs to suicides among younger people, there had also been evidence the pills may reduce the risk in the elderly, Anders Carlsten and Margda Waern of Gothenburg University reported in the BioMed Centraljournal BMC Geriatrics.

They reviewed the records of 85 men and women older than 65 who had committed suicide and compared them with a group of elderly people from among the general population who did not kill themselves.

After adjusting for psychiatric conditions, the patients who took sedatives and hypnotics for sleeping problems were four times more likely to commit suicide, Carlsten's team found.

"Clinicians need to be aware of this as these drugs are widely prescribed to the elderly," they wrote.

According to the World Health Organization, 877,000 people worldwide kill themselves each year. For every suicide death, anywhere from 10 to 40 attempts are made, the U.N. agency estimates.

Scientists have linked sleep disturbances to increased suicidal risk in people with psychiatric disorders and in adolescents but it is unclear whether the association also exists in the general population.

"A careful evaluation of the suicide risk should be carried out when an elderly person presents with symptoms of anxiety and sleep disturbance," the researchers wrote.

While they do not know exactly why, Carlsten and Waern suggested that the drugs somehow trigger aggressive or impulsive behavior or provide the means for people to take an overdose.

Disabilities or sleep problems may make people more likely to commit suicide, they added.

"Persons with these problems might be more likely to seek health care and perhaps more likely to receive prescriptions for psychotropic drugs," they wrote.