The answer is simple: It's unclear, because the study design they did cannot answer such questions.
This is one of the most basic misunderstandings in interpreting scientific studies. If you have "we saw x where we also saw y" then it can mean anything from "x causes y" to "y cause x". And also "unknown factor z causes both x and y", "it's a random coincidence", "they looked into the data long enough with enough different methods to find something" or a combination of all of those.
This is one of the most basic misunderstandings in interpreting scientific studies. If you have "we saw x where we also saw y" then it can mean anything from "x causes y" to "y cause x". And also "unknown factor z causes both x and y", "it's a random coincidence", "they looked into the data long enough with enough different methods to find something" or a combination of all of those.