Poor people are more likely to take high-interest loans/advances, and people who take high-interest loans are more likely to be poor. You can suggest causation

Poor people are more likely to take high-interest loans/advances, and people who take high-interest loans are more likely to be poor. You can suggest causation both ways if say, you study a group of middle-class people who took high-interest loans and find them more likely to be poor years later. If A causes B but B also causes A is it wrong to say causality goes both ways? A is both cause and effect. B is both cause and effect. I think this is nearly as common as causality going one way (like if we found that smoking causes cancer, but cancer causes people to be less likely to smoke).