The variance of forearm blood flow as an indicator of emotional stress.

Forearm blood flow was measured four times per minute by venous occlusion plethysmography during rest and during a brief emotionally stressful mental task. During emotional stress not only was the mean forearm blood flow increased, but the single blood flow values fluctuated more than at rest. The greater fluctuation, expressed statistically as the variance, was an indicator of emotional stress, at least as sensitive as the mean increase in the blood flow. Both a tranquillizer (thioridazine) and a beta-blocker (toliprolol) reduced the greater variance during the emotionally stressful situation in doses insufficient to diminish the mean increase in forearm blood flow.