A historical and philosophical analysis argues that mistrust of consciousness in early 20th-century psychology did not originate solely with behaviorism. William James, writing before John Watson's 1913 manifesto, already expressed unease about consciousness. James's critique stemmed from his opposition to perceptual elementarism—the view that mental states are composed of atomic sensory elements. He argued that just as no isolated sensory elements can be found in conscious experience, no pure consciousness can be separated from its contents. This argument relied on rejecting appeals to unconscious mental processes as unobservable, mirroring his skepticism about introspecting consciousness itself.
Both pharmacological and non-pharmacological treatments for depression activate TrkB receptors—a known antidepressant target—by inducing a physiological response linked to sedation. Rapid-acting antidepressants trigger TrkB signaling by evoking a state characterized by electroencephalographic slow-wave activity, behavioral immobility, reduced cerebral glucose utilization, and lowered body temperature. This signaling was not impaired in animals with reduced activity-dependent BDNF release but was diminished by maintaining animals in a warm ambient temperature. Preventing the hypothermic response attenuated the behavioral effects of the rapid-acting antidepressant nitrous oxide. The findings suggest that changes in energy expenditure and thermoregulation are essential, but not sufficient, for antidepressant responses, challenging pharmacology-centric hypotheses and highlighting the role of bioenergetics and thermoregulation.