WASHINGTON (Reuters) - Two studies published on Monday added to the growing evidence that the most popular class of drugs taken to treat depression may contribute to fragile bones in elderly people.The research focused on a class of antidepressant drugs called selective serotonin reuptake inhibitors. Millions of people, including many elderly, take these drugs, known as SSRIs, which include Eli Lilly and Co’s Prozac, known generically as fluoxetine.