What is the study of how psychological issues affect physical illness called?

Quick using the information in the graph, one might speculate that a) w. w.i created increased job opportunities in the u. s. b) the election of president hoover in 1936 caused unemployment to decline. c) the return of soldiers following w. w.ii caused unemployment to increase in the u. s. d) the new deal programs of president roosevelt created employment opportunities in the u. s.