But a new systematic research review from Mayo Clinic, one of the country’s leading medical centers, warns there’s still a lot to learn about CBD. The big takeaway from the review is that no one knows exactly how effective or safe CBD really is. The researchers argue that more research on humans is needed to confirm many of the health claims made on the packaging of products containing CBD, short for the Cannabis-derived compound cannabidiol… The Mayo Clinic encourages physicians to keep “a clinical curiosity and a healthy skepticism” about CBD.