Associations between T and depression measured with the items from the Diagnostic Interview Schedule
T-squared has a significant relationship with depression, indicating a curvilinear relationship. Among men whose testosterone is below 590 ng/dL, each increase in the testosterone level is associated with less depression. Among men whose testosterone is above this value, each increase in the hormone is associated with greater depression.
Depressed men had lower BT levels and TT levels than controls. Biochemical hypogonadism (i.e., BT level ≤ 2.4 nmol/L or TT level ≤ 12.14 nmol/L) was also more prevalent in depressed men than in non-depressed controls (34% versus 6% and 61% versus 14%, resp.).