For the single word, two might satisfy your description. First, and perhaps best by reason of its frequency and conformance with the meaning you described, is 'interdependent' or 'interdependence':
interdependent, adj. or interdependence, n.
adj.: Dependent each upon the other; mutually dependent.
n.: The fact or condition of depending each upon the other; mutual dependence.
(Definitions from OED Online.)
Another possibility, although much less common and perhaps suited only to technical uses (for example, in systems theory), is 'interdetermination':
cause and effect operating among several factors : multiple causation.
(Definition from Merriam Webster Unabridged.)
A thorough and agreed upon definition of 'interdetermination' is not easy to come by. The definition varies with the specialized field of application. Sir Joseph Larmor, for example, an Irish physicist and mathematician, used the term in a theoretical physics treatise titled "Questions in Physical Interdetermination" (1920, in the Proceedings of the International Congress of Mathematicians). For nontechnical audiences, the best description of his meaning I could find in the paper was this:
Such complete interdetermination is a very remarkable mode of relation. It involves that knowledge of change in any small part of a system determines the change throughout: that each part is in a sense the cause of the whole. The familiar relation of cause and effect has thus vanished, along with all its metaphysical perplexities: every part of the set of
concurrent events is now the determining cause of all the remainder.
Perhaps more usefully and certainly more recently, in a book titled Mutual Causality in Buddhism and General Systems Theory (Joanna Macy, SUNY Press, 1991), the term is used in a general sense:
The expressions mutual causality, reciprocal causality, dependent co-arising, interdependence, and interdetermination are, for the purposes of this book, taken as roughly equivalent in meaning.
Later in the same work, a definition of 'interdetermination' is quoted from Ervin Laszlo (originator of Systems Philosophy as a formal discipline):
Now interdetermination implies a dual relation between cause and effect...A determines B and B determines A...The reciprocity of the causality connecting A and B consists in this: as a result of a cause emanating from A, B manifests a modification in its relations to A, which modification itself can be regarded as the cause produced by B, acting on A, and resulting from the effect of the primal cause (A acting on B).