"... Her retrospective “volunteers” were former American soldiers enrolled in what was known as the Vietnam Experience Study. In 1985 almost 4,500 veterans of t

"... Her retrospective “volunteers” were former American soldiers enrolled in what was known as the Vietnam Experience Study. In 1985 almost 4,500 veterans of that war volunteered for extensive medical and mental examinations ..." I'd like to see another study with a broader selection of participants because the sample chosen is already self-selected.