In the 1960s, Dr. Becker worked with Howard Friedman, a psychologist, in an experiment involving the effects of low-frequency magnetic fields on histopathological changes in the central nervous system in rabbits. Following relatively brief exposures, Friedman had observed unusual abnormalities in brain tissue that appeared to be due to the magnetic field. But Friedman also observed the abnormal changes in the brains of the control rabbits, suggesting that the magnetic field was not the causative factor. As I heard the story, Dr. Becker asked Friedman whether the abnormal changes were seen with the same frequency in the exposed and control groups. Upon checking the slides, Friedman concluded that the changes occurred more often in the exposed group. Dr. Becker knew that laboratory rabbits were commonly infected with a virus that, although present, normally did not cause pathological changes. When the rabbit was subjected to stress, however, the ability of the animal’s immune system to hold the virus in check was weakened, resulting in the loss of control in some animals, and the consequent increased frequency of pathophysiological changes. This, Becker speculated, was what happened when the rabbits were exposed to the magnetic field, implying that the field was a stressor.

The mechanism of stressors was first proposed by Hans Selye, who described the role of corticoids as the classic biochemical mediator of the body’s response to any nonspecific stimulus. Friedman tested Dr. Becker’s hypothesis about the role of EMFs in causing stress by determining whether animals exposed to magnetic fields exhibited higher corticoid levels. He found higher levels of corticoids in animals that were exposed to magnetic fields, suggesting that Dr. Becker’s theory was correct (see H. Friedman and R.J. Carey: Biomagnetic stressor effects in primates, Physiol. Behav. 9:171–173, 1972).