First author Dr. Sarah M. Hartz, assistant professor of psychiatry at Washington University, and colleagues said the finding is of particular concern because individuals with severe mental illness are more likely to die younger than people without severe psychiatric disorders.
The researchers analyzed smoking, drinking and drug use in nearly 20,000 people including 9,142 psychiatric patients diagnosed with schizophrenia, bipolar disorder or schizoaffective disorder.
The investigators also assessed nicotine use, heavy drinking, heavy marijuana use and recreational drug use in more than 10,000 healthy people without mental illness.
The study, published in the journal JAMA Psychiatry, found 30 percent of those with severe psychiatric illness engaged in binge drinking, defined as drinking four servings of alcohol at one time. In comparison, the rate of binge drinking in the general population was 8 percent.
In addition, among those with mental illness, more than 75 percent were regular smokers. This compares with 33 percent of those in the control group who smoked regularly. There were similar findings with heavy marijuana use: 50 percent of people with psychotic disorders used marijuana regularly, versus 18 percent in the general population.
Half of those with mental illness also used other illicit drugs, while the rate of recreational drug use in the general population is 12 percent, the study said.
"I take care of a lot of patients with severe mental illness, many of whom are sick enough that they are on disability," Hartz said in a statement. "And it's always surprising when I encounter a patient who doesn't smoke or hasn't used drugs or had alcohol problems."
During the last few decades, smoking rates have declined in the general population. For example, about 40 percent of those age 50 and older used to smoke regularly; among those age 30 and younger, fewer than 20 percent have been regular smokers. But among the mentally ill, the smoking rate is more than 75 percent, regardless of the patient's age, Hartz said.
"With public health efforts, we've effectively cut smoking rates in half in healthy people, but in the severely mentally ill, we haven't made a dent at all," she said.