Correlation does not always mean causation because two variables can be related without one directly causing the other. There may be a third variable ...
Correlation does not always mean causation because two variables can be related without one directly causing the other. There may be a third variable involved, or the direction of the relationship may be unclear. For example, ice cream sales and drowning cases often increase at the same time, but ice cream does not cause drowning. A third factor, such as hot weather, affects both.
In my own correlation matrix, the relationship between perceived stress and negative affect could be mistaken for cause and effect because it was quite strong. However, this result does not prove that stress directly causes negative affect, or that negative affect causes stress. It is also possible that both are influenced by other factors, such as personality, coping style, or life situation. Since correlation only shows association, it should be interpreted carefully.