There is no English word which means what you explain. You would need to use more than one word, and there is no good phrase that fits every context you might want to use that idea in. "Mutual" can be an adverb or an adjective describing two things having something in common. Maybe "Mutual Causation" instead of "Reciprocal Causation” "Reciprocity" is a noun meaning when one thing does something for another thing, that thing responds in kind. "Circular logic" is a noun phrase. It describes a bad way of thinking which ends at the same place it began. Like "the sky is blue; therefore the sky is blue"

No exact matches, but a few related ideas: In casual speech, you might try something like "build on each other": "Curiosity and knowledge build on each other. The more you know, the more curious you will become, and vice versa." "Cause each other" might work: "Poverty and corruption cause each other. When one increases, so does the other." In some cases, you might be able to anthropomorphize with "scratch each other's backs": "Education and healthcare scratch each other's backs: as a population becomes more educated, it usually becomes healthier, and healthier populations are better able to learn." Some related concepts in formal speech: "If and only if" means that two things imply each other, rather than cause each other. "If a cat is in my house, it must be my cat. Since I never let my cat go outside, my cat must be in my house. That cat is my cat *if and only if* it is in my house."; "The Saudi economy and the oil market are closely linked. The Saudi economy will prosper if and only if the price of oil remains high." In math, logic, and computer science, "if and only if" is often abbreviated as "iff". A "vicious cycle" or (less commonly) a "virtuous cycle" might be closer to what you want. "The McClintoc family killed my father, so I killed one of their sons in revenge. Then they killed my mother as revenge for me killing their son, so I am about to kill their daughter. It's a vicious cycle." "Positive feedback loops" are also in the same group: an effect amplifies its own cause. "When the globe warms, ice melts, revealing land and water. Ice reflects most of the light that hits it, while land and water absorb light, which creates heat, accelerating global warming, which causes even more ice to melt. Positive feedback loops like this make global warming an even more intractable problem." "are correlated" shows that things are linked without making any assumptions about causation: "Life expectancy and happiness are correlated."

That’s good question. Can you give an example of A and B causing each other?

'The paradox of causality.'