Logically -- scientifically -- a runny nose might not be said to be "a sign of a cold". That is, it is not sufficient evidence to indicate a cold. When paired with other data, it may contribute to a diagnosis. It's not unrelated.
Similarly, an imaginary friend is not "a sign of" loneliness. On its own. When grouped with other data, maybe together they are.
It's just a difference in language usage. "A sign of X" might be taken to mean that on its own, X is implied. Or it might be taken to mean that it can be a contributing factor, but on it's own is meaningless.
Similarly, an imaginary friend is not "a sign of" loneliness. On its own. When grouped with other data, maybe together they are.
It's just a difference in language usage. "A sign of X" might be taken to mean that on its own, X is implied. Or it might be taken to mean that it can be a contributing factor, but on it's own is meaningless.