Absence of evidence is not evidence of the absence. Following is how a research review of the effectiveness of parachutes might be concluded: “There is no conclusive evidence that parachutes are effective at helping skydivers.” Ridiculous? Yes. Yet accurate and absurd!
And perhaps the biggest problem I have with this study about backpacks and adolescent back pain is that an overuse syndrome usually does NOT cause pain in the early stages. When the body is physically stressed by something like carrying a backpack, it often requires many years before the overuse results in pain.