Suppose a study finds a negative correlation between levels of a particular enzyme in the brain and the severity of mania in people suffering from bipolar disorder. Which of the following is the most accurate conclusion to make based on this evidence
A. Low levels of the enzyme cause bipolar disorder.
B. There is no relationship between the enzyme and mania.
C. Having low levels of the enzyme is associated with high mania.
D. Having high levels of the enzyme is associated with mania.