PSYCHIATRIC ANNALS 39:2 | FEBRUARY 2009 PsychiatricAnnalsOnline.com | 81 The Duration of Deployment and Sensitization to Stress T his article addresses conceptual and theoretical issues concerning how the duration of deployment to a combat theater of operations may impact the mental health of deployed troops. A core principle of occupational medicine, critical to this aim, is to identi- fy hazardous exposures in the workplace and define levels of acceptable exposure to those hazards. The known relationship between combat exposure and combat stress reactions, and the long-term risk of posttraumatic stress disorder (PTSD), is well established. 1 However, the criti- cal issue of the duration of exposure and its impact on the delayed emergence of symptoms has not been analyzed. To date, the literature has not considered the underlying mechanisms that might medi- ate the adverse effects of duration of de- ployment in relation to PTSD. Alexander C. McFarlane, MD, MBBS (Hons), Dip. Psychother, FRANZCP, is Professor of Psy- chiatry, Centre for Military and Veterans Health, University of Adelaide, Adelaide, Australia. Address correspondence to: Alexander C. Mc- Farlane, MBBS (Hons), Dip. Psychother, FRANZCP, Centre for Military and Veterans Health, Univer- sity of Adelaide, Level 2, 122 Frome Street, Ade- laide, SA 5000, Australia; fax +61 8 8303 5368; or email alexander.mcfarlane@adelaide.edu.au. Dr. McFarlane has disclosed no relevant fi- nancial relationships. Alexander C. McFarlane, MD, MBBS (Hons), Dip. Psychother, FRANZCP © 2009 iStock International Inc. 3902MacFarlane.indd 81 3902MacFarlane.indd 81 2/4/2009 1:55:48 PM 2/4/2009 1:55:48 PM