RT Journal Article SR Electronic T1 Treatment-resistant depression in later life JF Journal of Psychiatry and Neuroscience JO J Psychiatry Neurosci FD Canadian Medical Association SP E34 OP E35 DO 10.1503/150114 VO 40 IS 6 A1 Heba El Bayoumi A1 Zahinoor Ismail YR 2015 UL http://jpn.ca/content/40/6/E34.abstract