Updated

Nearly one-third of U.S. veterans who are given psychiatric medications by their doctors do not have a diagnosed mental health problem, according to a new study.

Older vets between ages 65 and 85 were the ones most commonly prescribed psychotropic drugs without a formal diagnosis, and were least likely to be receiving mental health treatment, researchers report in the American Journal of Geriatric Psychiatry.

The findings are important because such drugs can pose serious health risks. "Psychiatric medications can save lives, but they can also cause harm," said Ilse Wiechers, a psychiatrist at Yale School of Medicine and lead author of the study.

"My work aims to ensure that older adults receive the right medicine for the right diagnosis in the safest way possible," she said.

The 1.85 million veterans in the study filled prescriptions during fiscal year 2010 for at least one psychiatric medication, and were identified by their national Veterans Health Administration pharmacy and encounter claims.

Information about the patients and their health issues was pulled from their medical records.

Patients older than 65 were prescribed psychiatric medications without a diagnosis 44 percent more often than were patients in their 40s.

The study took into account whether the drugs were given to treat other problems, such as pain, seizures and headaches, and whether or not the physicians prescribing the pills were mental health specialists.

Among the people getting psychiatric drugs, just 39 percent of those who were not getting mental health treatment from specialists had a mental illness diagnosis. In contrast, 98 percent of those getting specialist mental health treatment had a diagnosed mental disorder.

The medications most likely to be over-prescribed were antidepressants; sedatives, such as alprazolam or diazepam and mood stabilizers, such as gabapentin and valproic acid.

It's unclear what these findings mean to older veterans and their families, according to Wiechers, as there are a number of possible explanations for over-prescribing these medications.

They include undiagnosed mental illness, incomplete documentation of mental health problems in the medical record and unnecessary administration of psychiatric medications.

"More research is needed before we can identify the most appropriate targets for change in clinical practice," Wiechers said. "Our next steps are to work together with our non-psychiatry colleagues to better understand what is happening on the ground in their day-to-day clinical practice."