According to the report, 25 percent of American workers experiences at least one mental or addictive disorder each year.

"The rates are extremely high," said Robin Hertz, study author and a senior director of population studies at Pfizer Pharmaceuticals Group, which paid for the research. "As a nation, we have to be more attentive to these types of problems. There is a mythology out there that if you are at work you are healthy. That is not really true."

The report found that companies pay more than $17 billion a year in "unproductive" wages to workers with mental disorders. Of that, $5 billion is paid to workers who miss workdays because of their alcohol or other drug addiction.

Researchers said the number of employees with addiction or mental-health problems is so high because people are not getting the treatment they need.

"It tells me people aren't seeking treatment. It's also possible when they go to a healthcare provider, there is a lack of attention to their problem," said Hertz. "Many people don't realize they can be helped. Or perhaps it's a matter of stigma. There is still a lot of misperception and shame around having a mental illness or a substance-abuse disorder. As a result, people hide it and don't seek care."

The study was based on data from the National Comorbidity Survey and the National Mortality Followback Survey.