WASHINGTON — Federal investigators say they have found evidence of widespread overuse of psychiatric drugs by older Americans with Alzheimer’s disease, and are recommending that Medicare officials take immediate action to reduce unnecessary prescriptions.

The findings will be released Monday by the Government Accountability Office, an arm of Congress, and come as the Obama administration has already been working with nursing homes to reduce the inappropriate use of antipsychotic medications like Abilify, Risperdal, Zyprexa and clozapine. But in the study, investigators said officials also needed to focus on overuse of such drugs by people with dementia who live at home or in assisted living facilities.

The Department of Health and Human Services “has taken little action” to reduce the use of antipsychotic drugs by older adults living outside nursing homes, the report said. Doctors sometimes prescribe antipsychotic drugs to calm patients with dementia who display disruptive behavior like hitting, yelling or screaming, the report said. Researchers said this was often the case in nursing homes that had inadequate numbers of employees.

Dementia is most commonly associated with a decline in memory, but doctors say it can also cause changes in mood or personality and, at times, agitation or aggression. Experts have raised concern about the use of antipsychotic drugs to address behavioral symptoms of Alzheimer’s and other forms of dementia. The Food and Drug Administration says antipsychotic drugs are often associated with an increased risk of death when used to treat older adults with dementia who also have psychosis.