Almost one fourth of all patient admissions in US community hospitals for patients age 18 years or older involve psychiatric diseases such as depression, bipolar disorder, and schizophrenia, or conditions related to substance use, according to an analysis of 2004 data released by the government’s Agency for Healthcare Research and Quality.

The current study presents the first documentation of the full impact of mental health and substance abuse disorders on US community hospitals: Roughly 1.9 million of the 7.6 million admissions involving psychiatric or substance use were for patients who were hospitalized primarily because of their mental health or substance abuse problem. In the other 5.7 million hospitalizations, patients were admitted for another condition but they also were diagnosed with a mental health or substance abuse disorder.

"Community hospitals play an important role in the treatment of people with mental health and substance abuse disorders," said Agency Director Carolyn M. Clancy, MD. "This report gives health care policymakers an in-depth look at the impact of mental health and substance abuse care on the health care system."

The Agency found that most patients with mental health and substance abuse disorders were older. For example, although people age 80 years and older accounted for only 5 percent of the population in 2004, they accounted for nearly 21 percent of all hospital admissions for these conditions -- principally for dementia. There were also gender differences. The most frequent admitting diagnosis for women was mood disorders, whereas it was substance abuse for men.

Furthermore, patients with both a mental health condition and a substance abuse disorder accounted for 1 million of the nearly 8 million admissions. Nearly half of these cases with dual diagnoses involved drug abuse, a third involved alcohol abuse, and one in five involved both drug and alcohol abuse.

In addition, 240,000 women hospitalized for childbirth or pregnancy also had mental health or substance abuse problems. Four of every 10 of these patients were between 18 and 24 years of age.

Suicide attempts accounted for nearly 179,000 hospital admissions. Of these, 93 percent involved a mental health condition -- most commonly mood disorders -- and/or substance abuse. Nearly three quarters of these patients were between ages 18 and 44 years and more than half were women. Poisoning, by overdosing prescription medicines or ingesting a toxic substance, was the most common way to attempt suicide.