Not only does the toxin keep your forehead wrinkle free, it keeps depression at bay as well. From Scientific American:

Botox injection

In the first randomized, controlled study on the effect of botulinum toxin—known commercially as Botox—on depression, researchers investigated whether it might aid patients with major depressive disorder who had not responded to antidepressant medications. Participants in the treatment group were given a single dose (consisting of five injections) of botulinum toxin in the area of the face between and just above the eyebrows, whereas the control group was given placebo injections. Depressive symptoms in the treatment group decreased 47 percent after six weeks, an improvement that remained through the 16-week study period. The placebo group had a 9 percent reduction in symptoms. The findings appeared in May in the Journal of Psychiatric Research.