From the given sentence, extract the phrase (often noun or verb) that carries the given relationship. The generated phrase should be present in the sentence.
Q: Given Relationship: 'be head by', Sentence: 'Cato Professor and Psychiatry Department Head at the University of Melbourne and Clinical Director of NorthWestern Mental Health Bruce Singh said many advances had been made in the understanding of cannabis use and its effects on cognition and psychotic conditions .'
A:
had