Yeah but you have to actually do a study to determine that relationship, which is exactly backwards from what this "study" did.

Flu rates are a much simpler metric than "most stressed," which is a very squishy phrase that they don't even bother to define. Afaik no one tracks stress levels nationally, and if they do, there's a million different ways that'll give you a million different answers. "How stressed are people" is a very different question from "how many people have the flu." Even if they wanted to do this right, it would be a lot harder because the CDC can't just give you a number for you to correlate with search data.

I get where you're coming from but I think there's a big difference between those two uses.

Googling symptoms of flu most likely means you think you have the flu and are using Google as a form of symptom checklist.

Googling stress relief methods could indicate you're stressed, or that you're doing research, curious, discussing different methods w friends & family, etc.

I don't think people are Googling "am I stressed (based on the following symptoms x y z)" - they already know they are - but they may not be sure whether they have the flu or a cold.

Correlation =/= causation.

Disappointing, though, because that's an interesting concept for a study - what factors contribute to stress and which areas of the country have the highest number of those factors.