Qi consists of equal and opposite qualities - Yin and Yang - and when these become unbalanced, illness may result. By inserting fine needles into the channels of energy, an acupuncturist can stimulate the body's own healing response and help restore its natural balance. The flow of Qi can be disturbed by a number of factors. These include emotional states such as anxiety, stress, anger, fear or grief, poor nutrition, weather conditions, hereditary factors, infections, poisons and trauma. The principal aim of acupuncture in treating the whole person is to recover the equilibrium between the physical, emotional and spiritual aspects of the individual.