Interrelated things are connected — they compliment or depend on each other. Your mood and whether or not you ate breakfast this morning might be interrelated, for example.
Most scientists agree that our minds and bodies are interrelated, since our emotions can affect our health, and physical injuries and illnesses can also affect our mood. Equally interrelated are issues of poverty and crime in major cities. Interrelated combines inter-, in Latin "between or among," and relate, which first meant only "recount or tell," but by the 1690s gained the meaning "bring something into relation with something else."