Botox functions by blocking the neurotransmitter acetylcholine from being released by the axon terminal of a neuron. Typically, acetylcholine binds to receptors on muscle, causing contraction; inhibiting this results in paralysis.
In the 1890s, psychologist William James promoted his facial feedback hypothesis. James believed there was a link between physical facial expressions and emotional states. Indeed, a number of studies in the 1980s and ’90s support this notion.
In the May issue of the Journal of Psychiatric Research, researchers M. Axel Wollmer and colleagues at the University of Basel in Switzerland reported that paralyzing the glabellar frown region—the area between the eyebrows—with Botox significantly improved symptoms in depressed individuals.