One of the things we kept coming back to in psychology was the idea that correlation does not always mean causation. This concept will stay with me five years into the future, because it came up with many of the experiments we studied, as well as in several widely believed concepts that aren't necessarily true. Now, when I hear about a correlation between two things, I never assume the first variable caused the second. I always consider that the second could have caused the first, that a third variable could have caused an increase in both, or that they may not be related at all and two separate variable caused them to increase individually.
Maybe I'm just skeptical, but I also keep the correlation/causation idea in mind when hearing news stories about different things that cause cancer or any various number of other diseases. I need to know more information, like is there just a correlation between the variable and cancer? Was any lab testing done to check this theory? Were the results replicated? I think too often, news stations jump to conclusions regarding causal relationships, and I will no longer blindly believe everything they tell me.