People who suffer from mental disorders ranging from anxiety to depression are far more likely than others to abuse alcohol or other drugs, scientists said Wednesday.

Interviews conducted with 20,291 people in the general community and in institutions found those with disorders such as phobias and panic attacks were more than twice as likely as those without such disorders to abuse alcohol or other drugs, said Dr. Darrel Regier of the National Institute of Mental Health in Bethesda, Md.The finding provides "clear and persuasive evidence that mental disorders must be addressed as a central part of substance abuse prevention efforts" in the United States, Regier and co-researchers said in the Journal of the American Medical Association.

The reasons for the high rates of co-existing mental problems and substance abuse are unclear, Regier said. Although some studies have suggested that mental disorders precede drug and alcohol dependency, he said there is "increasing argument" that certain disorders are the result - not the cause - of substance abuse.

Researchers conducted interviews during a four-year period with adults ages 18 and older in communities in five geographical areas and with occupants of mental institutions, prisons and nursing homes. The scientists recorded the percentage who experienced either mental disorders or substance abuse or both.

Mental disorders were classified into four primary categories: schizophrenia; "affective" disorders such as major depression; antisocial personality disorder; and anxiety including phobias and panic disorder.

The study found that among those with any lifetime diagnosis of a mental disorder, 22.3 percent had a history of alcohol abuse, compared with 11 percent of those with no such diagnosis.

For drugs other than alcohol, the comparative risk of addiction among those with mental problems was even greater. Among those with disorder diagnoses, 14.7 percent were classified as "drug abuse dependent" compared to only 3.7 percent of those with no mental disorders.

In addition, Rieger said people with a lifetime history of alcoholism were twice as likely as others to suffer from mental disorders and six times more likely to suffer from forms of drug dependency.

Among those with a history of drug abuse, 53 percent had a mental disorder - the highest rate of combined disorders among those studied.

Researchers also found that people in institutions, who make up about 1.3 percent of the population in the United States, were more than twice as likely to suffer some form of mental disorder as others.