What is the difference between "suffer for" and "suffer from"?

"Suffer for" introduces a reason for punishment or suffering that is typically caused by other human beings, and which people either choose to accept because of what they believe in, or are forced to endure because of their past actions (this is the sense in "suffer for my sins"). "Suffer from" is used to identify a disease or ailment, and doesn't have the same moral element.

Suffer for The OED has examples of this under meaning "3 a. To undergo or submit to pain, punishment, or death." Examples it gives include "Every Man is obliged to suffer for what is right, as to oppose what is Unjust." "It was a hard thing to suffer for an opinion; but there are times when opinions are as dangerous as acts." In this case the phrases "for what is right" and "for an opinion" are using the sense of "for" that expresses a goal or cause. Hence "for" introduces the reason or purpose for the suffering, and it is typically connected with punishment or suffering on account of human action.

Suffer from This expresses (OED 3 b) suffering due to "a disease or ailment", examples "She had suffered much from disease." "She was suffering from what she was pleased to call a fit of depression." Here the suffering is based on a physical cause.

See: "suffer, v." OED Online. March 2021. Oxford University Press. (accessed May 06, 2021).