I wrote this sentence recently, where I used the preposition at after the word anxiety.
I suppose they1 are valuable in that they reveal our anxiety at being human.
I'm not sure if the preposition at can properly follow anxiety in this way. I may have done it for the sake of euphony, i.e. at rhymes with that.
A quick search on ngrams shows that the phrase "anxiety at" is indeed used, more than "anxiety concerning" and a little less than "anxiety on". The phrase "anxiety over" has a substantial edge and "anxiety about" is most common by far.
But this research is by no means conclusive. It just shows that "anxiety about" is the most common. Which preposition would you choose to complete the sentence? Do you think that using at this way is a good choice, or would most people flag it as suspicious?
1 The pronoun here refers to the theories of free will and determinism. To give more context, I was debating whether these theories are useful or just fun to think about.