Which of the following is most likely to foster stronger immune functioning?

A) an external locus of control
B) social support
C) a Type A personality
D) increased cortisol levels

Social support has been found to have a positive impact on immune functioning by reducing stress and promoting positive emotions. An external locus of control (A) has been associated with increased stress and negative health outcomes. Type A personality (C) is often associated with high stress levels and an increased risk for heart disease. Increased cortisol levels (D) indicate elevated stress levels which can have a negative impact on immune functioning.