Sweet basil is a powerful anti-depressant oil and is well suited to calming blends, especially where there is a lack of focus and a need to reverse mental fatigue and nervous tension.  In aromatherapy Sweet Basil is used to soothe sore, aching muscles, and to treat depression and other conditions of the mental state, where the fragrance is very soothing.  Basil linalool essential oil is also a great choice as a gentle decongestant.  It's a great oil for diffusing in  a study room where it will improve mental clarity and concentration.