In this video, as part of The Motley Fool's "Ask a Fool" series, health-care analyst David Williamson takes a question from a Fool reader, who asks:

Gilead Sciences (NASDAQ:GILD) seems to be on a down trend. Is there any specific reason, or should I just hold firm?

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.