When a Yaksha spirit by some means or other enters the body of a human being, he immediately turns mad. Such a spirit is called the Yaksha spirit.
आविशन्ति च यं यक्षाः पुरुषं कालपर्यये। उन्माद्यति स तु क्षिप्रं ज्ञेयो यक्षग्रहस्तु सः।।५३