unter Stress **stehen**... not **sein** instead?

Question

In the Langenscheidt I found this expression:

unter Stress stehen (1.)

Then I consulted also the Duden:

im S. sein; im/unter S. stehen (2.)

where S. stands for stress.

In other words, as far as the context of Stress is concerned, one can use the prepositions in and unter with stehen, but not with sein. More simply put, I cannot say: unter Stress sein. Why not? Why does it work only with stehen? What are the subtle differences in imagery (which I am not catching) that these two verbs evoke, such that unter is possible with the first, but not with the latter?

Answer 1

Unter Stress stehen is a collocation. You can replace Stress with a handful of semantically similar words, like Spannung, Strom, Druck, or remote words like Arrest, Schutz, Beobachtung, Narkose, …. Only with Stress, you have the equivalent option of in/im … sein.

As for imagery, which I do think is a great way to remember: Imagine your boss as a giant. He/she is treading on you. You're standing straight, raising your arms and bracing your body, struggling to not succumb under his/her sole.

Answer 2

Both forms are correct and used in standard German:

"Ich bin unter Stress." is the same as "Ich stehe unter Stress."

You can use the forms synonymously.

The form "unter Stress stehen" is, maybe, a little more elegant.