Can botulinum toxin improve mood in depressed patients?

Depression has a number of significant symptoms such as depressed mood, lack of volition/energy, suicidal ideation, low concentration, sleep disturbance, anger, anxiety, psychomotor retardation, fear and sadness. In addition, various facial expressions such as frowning and sadness can also be easily recognized in depressed patients. In fact, major muscles involved in the development of such negative emotion have been reported in depressed patients, for instance, corrugators and procerus muscles in the glabellar regions of the face. Electromyography studies have also reported that depressed patients had overactivity of such grief muscles during different affective imagery paradigms. Furthermore, subjective emotion has also been found to be affected by differential facial expression via an image feedback system. Interestingly, anecdotal open-label studies have shown that botulinum toxin may have a role in treatment of depression and a recent randomized-placebo controlled study has also confirmed the effect of botulinum toxin in reduction of depressive symptoms for the first time. This article will discuss the putative role of botulinum toxin in a treatment of depression in the context of the clinical significance, limitations and future research directions.