PORTLAND -- It's all in their heads.

That's the conclusion Dr. Laurence Binder came to after examining 18 construction workers who claim they were exposed to sarin five years ago while working at the Umatilla Chemical Depot.

"I'd classify it as mass hysteria," the Beaverton-based neuropsychologist testified Wednesday in Portland during the federal trial in which 49 workers are suing the Army for negligence.

About four dozen workers simultaneously became ill Sept. 15, 1999, while building the incinerator plant near where the Army stores 3,717 tons of sarin and mustard agent. The workers were treated for chest and eye pain, coughing, vomiting and trouble breathing.

Since then, many of the workers still complain of depression, reduced lung capacity and sensitivity to strong odors. Some have been diagnosed with post-traumatic stress disorder and reactive airway disease.

The Army denies chemical agent was the cause of their illnesses.

Binder told U.S. District Court Judge Dennis Hubel that while many of the workers he examined had some cognitive disorders, anxiety and depression, none of the symptoms is related to the incident.

Alcoholism, abusive relationships and other health problems could cause the symptoms, he said.

Binder said one worker, Matt Greenup, who now lives in Portland, had symptoms of depression, paranoia and anxiety disorders. Although another doctor diagnosed Greenup with post-traumatic stress disorder, Binder disagreed, saying the onset of the disorder can only follow a "real" event.

"Is your opinion there was no PTSD based on your belief there was no exposure?" Hubel asked Binder.

"It's based on my belief they were exposed to an irritant instead of (chemical agents)," Binder replied.

"If there was a sarin exposure, then would your opinion of Greenup's PTSD change?" Hubel asked.

"Yes," Binder said.

Binder also testified that worker Dave Bosley's health problems likely were caused by the stress of financial difficulties.

He said while Bosley, who lives in Milton-Freewater, complained of multiple chemical sensitivity, there is no medical explanation for the symptoms. Binder concluded Bosley's illness must be psychosomatic.

"People with (multiple chemical sensitivity) aren't actually chemically sensitive," Binder said. "They just think they are."

But James McCandlish, the Portland-based attorney representing the 49 workers, noted that the symptoms for multiple chemical sensitivity were similar to reactive airway disease, which can be caused by chemical exposure.

Closing arguments in the case could happen as soon as Friday, but it could be months before Hubel hands down a decision in the case.