Depression triples the likelihood that a nursing home resident with dementia will be physically aggressive, a new study shows.

Delusions, hallucinations and constipation also appeared to be risk factors for physical aggression in these patients, Dr. Ralph Leonard of CALM-MD, LLC, in St. Louis Park, Minnesota and colleagues from Yale Medical School found.

About 7 percent of the 1.3 million people living in U.S. nursing homes become physically aggressive each week, which can be traumatic for the residents and the staff as well, the authors note. To investigate whether any potentially treatable factors are associated with this behavior, Leonard and his team studied 103,344 nursing home residents in five states. All of the subjects were older than 60 years and had been diagnosed with dementia.

During the week before the data were collected, 6.9 percent had been physically aggressive, while 10.5 percent had been verbally aggressive.

Residents with depressive symptoms were 3.3 times more likely to have been physically aggressive, and those experiencing delusions had twice the risk of aggression. Hallucinations increased the likelihood of physical aggression by 40 percent, while constipation was linked with a 30-percent increase risk.

The same factors were associated with verbal aggression, except for constipation.

While several other studies have found an association between depression and physical aggression among nursing home residents, no published study of treatment for this behavior included an antidepressant, Leonard and his team point out.

“Thus, the relative importance of depression as a potentially modifiable risk factor may not be recognized,” they write in the Annals of Internal Medicine.

It is not clear why constipation might increase the risk of aggressive behavior, the researchers note. They suggest that residents may lash out defensively as a reaction to the symptoms of constipation itself or to invasive treatments for constipation, such as suppositories.

All of these factors may be treated or modified, and if intervention is successful, it may reduce the risk of violence and harm by these nursing home residents, the researchers conclude.

SOURCE: Archives of Internal Medicine, June 26, 2006.