BMC Public Health 2007, 7:277 http://www.biomedcentral.com/1471-2458/7/277 16. Leon AC, Olfson M, Portera L, Farber L, Sheehan DV: Assessing psychiatric impairment in primary care with the Sheehan Disability Scale. Int J Psychiatry Med 1997, 27:93-105. 17. Kroenke K, Spitzer RL, Williams JBW: The PHQ-9: validity of a brief depression severity measure. J Gen Intern Med 2001, 16:606-613. 18. Reilly MC, Zbrozek AS, Dukes EM: The validity and reproducibil- ity of a work productivity and activity impairment instru- ment. PharmacoEconomics 1993, 4:353-365. 19. Craig CL, Marshall AL, Sjöström M, Bauman AE, Booth ML, Ains- worth BE, Pratt M, Ekelund U, Yngve A, Sallis JF, Oja P: Interna- tional Physical Activity Questionnaire (IPAQ): 12-country reliability and validity. Med Sci Sports Exerc 2003, 35:1381-1395. Pre-publication history The pre-publication history for this paper can be accessed here: http://www.biomedcentral.com/1471-2458/7/277/pre pub Publish with Bio Med Central and every scientist can read your work free of charge "BioMed Central will be the most significant development for disseminating the results of biomedical research in our lifetime." Sir Paul Nurse, Cancer Research UK Your research papers will be: available free of charge to the entire biomedical community peer reviewed and published immediately upon acceptance cited in PubMed and archived on PubMed Central yours — you keep the copyright Submit your manuscript here: http://www.biomedcentral.com/info/publishing_adv.asp BioMedcentral Page 9 of 9 (page number not for citation purposes)