What's the Difference Between the Facts and the Conclusions?

Many studies are cross sectional, in the sense that they look at people only once. Oftentimes researchers use language like drug users brains have atrophied or you see this decrease in volume. Yet they only tuk a measure of the person's brains one moment in time and so they can't say anything about a change. But oftentimes he do. And that's a clear violation of what they can actually say with their current methods.