Finger tremor between 2 and 32 hertz in frequency was measured in two groups of anxious subjects. In one study 32 normal subjects were made acutely anxious by experimental stressors, and their tremor was measured and compared with rest conditions. In a second study, tremor was measured in 28 chronically anxious psychiatric patients and in 28 control subjects matched for age and sex. No differences were found in the peak frequency of tremor in any of the groups, but the amount of tremor was greater in the anxious subjects. The differences were greatest at tremor in the frequency range between 6 and 17 Hz. The results support the view that the differences between normal and anxious tremors are those of degree, not of nature.
Tyrer PJ, Lader MH. Tremor in Acute and Chronic Anxiety. Arch Gen Psychiatry. 1974;31(4):506-509. doi:10.1001/archpsyc.1974.01760160056012