A recent study by the Department of Psychology at Columbia University demonstrated that patients who received Botox injections for their frown lines exhibited less negative emotional experiences.  It actually makes sense!  Just as any other muscles do when contracted, the facial muscles will send feedback to the brain not only letting the brain know they are contracting, but also sending signals to the emotional center of the brain telling it, "I'm frowning because I am upset!".  By preventing or weakening these "frown" muscles, the emotional center of the brain can receive less of these negative emotions and more positive stimulation making you happy!