1. A non-invasive method to determine the cerebral hemodynamics in a human subject with depression using a plurality of ultrasound devices comprising, steps of: (a) obtaining a subject's percent carotid stenosis in a right external carotid artery and a left external carotid artery using B-mode and Doppler measurements; (b) obtaining mean blood flow velocity for the left and right side of a subject for all major cerebral arteries including internal carotid arteries, middle cerebral arteries, anterior cerebral arteries and posterior cerebral arteries; (c) comparing the percent carotid stenosis in both right and left to normal limits; (d) determining if the percent carotid stenosis of one side is greater than the other; (e) determining if mean blood flow velocity in the right or left anterior cerebral artery is lower than normal limits; (f) determining if the mean flow velocity of one side of the anterior cerebral artery is greater than the other; (g) determining if there was a right or left anterior cerebral artery hyperperfusion; (h) determining if there was a right or left anterior cerebral artery hypoperfusion; (i) determining if mean blood flow velocity in the right or left posterior cerebral artery are lower than normal limits; (j) determining if mean blood flow velocity of one side of the posterior cerebral artery is greater than the other; (k) determining if there was a right or left posterior cerebral artery hypoperfusion; (l) determining a DSM-IV score using the standard questionnaire; (m) determining if a DSM-IV score was greater than or equal to five; and (n) determining if a cerebral hemodynamic model is associated with depression based on the determination of steps (d) through (m).