Estimating the impact or consequences of health conditions on populations has understandable policy appeal. Using mortality as an index of that impact has implicit attraction: it is a final and irrevocable outcome and its definitiveness as a measure is not open to question. Once we go beyond mortality as an index of disease outcome, several opportunities present themselves. But so do several challenges. The Global Burden of Disease studies have embodied both these opportunities as well as the challenges. Estimating the impact of mental disorders, especially in the context of comparisons with physical diseases, poses an added challenge. The subjective nature of many of the features of mental illness, the imprecision of their measurement and the spectrum pattern of the distribution of many of the symptoms make mental disorders open to either problem deflation or inflation. The reliability of the various tools for assessing and classifying mental health conditions gives some assurance about the fact that these are real entities, albeit often defined in abstract terms, but the rather poor validity for many of these disorders leads not only to frequent shifts in their boundaries but also to the fact that a sizeable section of the community will remain sceptical about their nature (Jablensky, Reference Jablensky2012).

It is within the context of these caveats that the impact of the Global Burden of Disease (GBD) studies can be appreciated. As noted by Baxter et al. (Reference Baxter, Ferrari, Erskine, Charlson, Degenhardt and Whiteford2014) the findings from these studies have led to policy attention that was hitherto not present and have given an impetus to advocacy efforts to demand for even greater attention. Baxter et al. sought to compare the latest GBD 2010 study (Murray et al. Reference Murray, Vos, Lozano, Naghavi, Flaxman, Michaud, Ezzati, Shibuya, Salomon, Abdalla, Aboyans, Abraham, Ackerman, Aggarwal, Ahn, Ali, Alvarado, Anderson, Anderson, Andrews, Atkinson, Baddour, Bahalim, Barker-Collo, Barrero, Bartels, Basáñez, Baxter, Bell, Benjamin, Bennett, Bernabé, Bhalla, Bhandari, Bikbov, Abdulhak, Birbeck, Black, Blencowe, Blore, Blyth, Bolliger, Bonaventure, Boufous, Bourne, Boussinesq, Braithwaite, Brayne, Bridgett, Brooker, Brooks, Brugha, Bryan-Hancock, Bucello, Buchbinder, Buckle, Budke, Burch, Burney, Burstein, Calabria, Campbell, Canter, Carabin, Carapetis, Carmona, Cella, Charlson, Chen, Cheng, Chou, Chugh, Coffeng, Colan, Colquhoun, Colson, Condon, Connor, Cooper, Corriere, Cortinovis, de Vaccaro, Couser, Cowie, Criqui, Cross, Dabhadkar, Dahiya, Dahodwala, Damsere-Derry, Danaei, Davis, Leo, Degenhardt, Dellavalle, Delossantos, Denenberg, Derrett, Des Jarlais, Dharmaratne, Dherani, Diaz-Torne, Dolk, Dorsey, Driscoll, Duber, Ebel, Edmond, Elbaz, Ali, Erskine, Erwin, Espindola, Ewoigbokhan, Farzadfar, Feigin, Felson, Ferrari, Ferri, Fèvre, Finucane, Flaxman, Flood, Foreman, Forouzanfar, Fowkes, Fransen, Freeman, Gabbe, Gabriel, Gakidou, Ganatra, Garcia, Gaspari, Gillum, Gmel, Gonzalez-Medina, Gosselin, Grainger, Grant, Groeger, Guillemin, Gunnell, Gupta, Haagsma, Hagan, Halasa, Hall, Haring, Haro, Harrison, Havmoeller, Hay, Higashi, Hill, Hoen, Hoffman, Hotez, Hoy, Huang, Ibeanusi, Jacobsen, James, Jarvis, Jasrasaria, Jayaraman, Johns, Jonas, Karthikeyan, Kassebaum, Kawakami, Keren, Khoo, King, Knowlton, Kobusingye, Koranteng, Krishnamurthi, Laden, Lalloo, Laslett, Lathlean, Leasher, Lee, Leigh, Levinson, Lim, Limb, Lin, Lipnick, Lipshultz, Liu, Loane, Ohno, Lyons, Mabweijano, MacIntyre, Malekzadeh, Mallinger, Manivannan, Marcenes, March, Margolis, Marks, Marks, Matsumori, Matzopoulos, Mayosi, McAnulty, McDermott, McGill, McGrath, Medina-Mora, Meltzer, Mensah, Merriman, Meyer, Miglioli, Miller, Miller, Mitchell, Mock, Mocumbi, Moffitt, Mokdad, Monasta, Montico, Moradi-Lakeh, Moran, Morawska, Mori, Murdoch, Mwaniki, Naidoo, Nair, Naldi, Narayan, Nelson, Nelson, Nevitt, Newton, Nolte, Norman, Norman, O'Donnell, O'Hanlon, Olives, Omer, Ortblad, Osborne, Ozgediz, Page, Pahari, Pandian, Rivero, Patten, Pearce, Padilla, Perez-Ruiz, Perico, Pesudovs, Phillips, Phillips, Pierce, Pion, Polanczyk, Polinder, Pope III, Popova, Porrini, Pourmalek, Prince, Pullan, Ramaiah, Ranganathan, Razavi, Regan, Rehm, Rein, Remuzzi, Richardson, Rivara, Roberts, Robinson, De Leòn, Ronfani, Room, Rosenfeld, Rushton, Sacco, Saha, Sampson, Sanchez-Riera, Sanman, Schwebel, Scott, Segui-Gomez, Shahraz, Shepard, Shin, Shivakoti, Singh, Singh, Singh, Singleton, Sleet, Sliwa, Smith, Smith, Stapelberg, Steer, Steiner, Stolk, Stovner, Sudfeld, Syed, Tamburlini, Tavakkoli, Taylor, Taylor, Taylor, Thomas, Thomson, Thurston, Tleyjeh, Tonelli, Towbin, Truelsen, Tsilimbaris, Ubeda, Undurraga, van der Werf, van Os, Vavilala, Venketasubramanian, Wang, Wang, Watt, Weatherall, Weinstock, Weintraub, Weisskopf, Weissman, White, Whiteford, Wiebe, Wiersma, Wilkinson, Williams, Williams, Witt, Wolfe, Woolf, Wulf, Yeh, Zaidi, Zheng, Zonies, Lopez, AlMazroa and Memish2012) with earlier efforts and to highlight differences and similarities in their findings. They noted that, in view of a vastly improved epidemiological terrain and substantial differences in methodology, the 2010 study was conducted under a set of more auspicious circumstances than the earlier ones. They concluded that it was not possible to compare the estimates arising from the latest study with those of 1990 and 2004. That conclusion is bound to be both reassuring, in so far as it indicates improved methodology, but also disappointing, given that the important possibility of comparing trends over the periods has been lost.

An important aspect of the improved methodology was the availability of representative epidemiological data from more countries than was available even for the GBD 2000–2004 revisions. This meant that direct data were available for some countries and regions for which extrapolations had been used in the earlier studies. Also, the omission of disorders of childhood from the earlier estimates was rectified in the GBD 2010. A second methodological improvement in the computation of burden in the GBD 2010 study is the use of the disease-modelling tool, DisMod-MR. By integrating expert opinions and experience with empirical data, DisMod-MR forced internal consistency on available epidemiological estimates of prevalence, incidence, remission, duration and excess mortality across countries, regions, time points, gender and age groups.

Using this improved methodology, the GBD 2010 found that mental and substance use disorders explained 7.4% of the total DALYs in 2010 (Degenhardt et al. Reference Degenhardt, Whiteford, Ferrari, Baxter, Charlson, Hall, Freedman, Burstein, Johns, Engell, Flaxman, Murray and Vos2013; Whiteford et al. Reference Whiteford, Degenhardt, Rehm, Baxter, Ferrari, Erskine, Charlson, Norman, Flaxman, Johns, Burstein, Murray and Vos2013). Reflecting the complexity of the exercise, this estimate was probably very conservative. For example, it was based on ‘direct burden’ where mental and substance use disorders are the direct cause of health loss and excluded excess (attributable) burden resulting from the increased risk of mortality and disability due to subsequent health outcomes captured elsewhere in GBD 2010. Indeed, as was subsequently shown (Ferrari et al. Reference Ferrari, Norman, Freedman, Baxter, Pirkis, Harris, Page, Carnahan, Degenhardt, Vos and Whiteford2014), mental and substance use disorders were responsible for 22.5 million of the 36.2 million DALYs allocated to suicide in GBD 2010.

The GBD 2010 is a historic accomplishment, building as it does on the considerable achievements of its forebears. The widening of the database on which the new estimates are presented and the strengthening of the methodology beyond what was used for the earlier studies should translate to greater confidence in the estimates of burden presented for mental and substance use disorders. Major challenges nevertheless remain. Our ability to overcome them would give hope that even better estimates of the burden of mental disorders will emerge in the future. The GBD studies would have been impossible without the remarkable progress made towards the development of a ‘common language’ by way of improved nosology and classification (Sartorius et al. Reference Sartorius, Kaelber, Cooper, Roper, Rae, Gulbinat, Ustun and Regier1993), progress that has made it possible not only for professionals to communicate among themselves and with patients, but also for cross-national comparisons to be possible. Even though there are still pockets of atavistic discontents with the claim that some mental health conditions are either non-existent or are the modern day equivalent of imperialism, the fact is that we now have the tools to demonstrate that not only do mental disorders exist everywhere but that their occurrence also constitutes major burden across cultures. Nevertheless, there is still much imperfection in our understanding of the validity of the disorders. Thus, while there is an expectation that recent and current efforts to improve these classifications will result in further improved reliability and utility, there is a general appreciation that the current knowledge in neuroscience and genetics cannot provide strong support for the validity of the existing categories.

The fundamental problem of lack of data from some countries, and even regions, of the world is unlikely to disappear soon. This lack of data is a reflection of a deeper problem of inequity in the way mental health resources are distributed across the globe. The GBD 2010 has dealt with this problem using sophisticated modelling procedures. But the lack of data from large regions of the world will remain a source of doubt about the veracity of any reported estimates of burden. International collaboration will be required to address this problem in the years to come. It is re-assuring that a broad cross-cultural agreement was obtained about the disability weights assigned to various health conditions and that efforts were made to obtain the views of community respondents from diverse regions of the world (Salomon et al. Reference Salomon, Vos, Hogan, Gagnon, Naghavi, Mokdad, Begum, Shah, Karyana, Kosen, Farje, Moncada, Dutta, Sazawal, Dyer, Seiler, Aboyans, Baker, Baxter, Benjamin, Bhalla, Abdulhak, Blyth, Bourne, Braithwaite, Brooks, Brugha, Bryan-Hancock, Buchbinder, Burney, Calabria, Chen, Chugh, Cooley, Criqui, Cross, Dabhadkar, Dahodwala, Davis, Degenhardt, Díaz-Torné, Dorsey, Driscoll, Edmond, Elbaz, Ezzati, Feigin, Ferri, Flaxman, Flood, Fransen, Fuse, Gabbe, Gillum, Haagsma, Harrison, Havmoeller, Hay, Hel-Baqui, Hoek, Hoffman, Hogeland, Hoy, Jarvis, Karthikeyan, Knowlton, Lathlean, Leasher, Lim, Lipshultz, Lopez, Lozano, Lyons, Malekzadeh, Marcenes, March, Margolis, McGill, McGrath, Mensah, Meyer, Michaud, Moran, Mori, Murdoch, Naldi, Newton, Norman, Omer, Osborne, Pearce, Perez-Ruiz, Perico, Pesudovs, Phillips, Pourmalek, Prince, Rehm, Remuzzi, Richardson, Room, Saha, Sampson, Sanchez-Riera, Segui-Gomez, Shahraz, Shibuya, Singh, Sliwa, Smith, Soerjomataram, Steiner, Stolk, Stovner, Sudfeld, Taylor, Tleyjeh, van der Werf, Watson, Weatherall, Weintraub, Weisskopf, Whiteford, Wilkinson, Woolf, Zheng, Murray and Jonas2012). Generating a broad international consensus for this type of exercise is a fundamental prerequisite for dealing with what is still essentially an imprecise science (Gureje & Stein, Reference Gureje and Stein2012). However, even here there is evidence that mental health conditions may not always be rated on the basis of objective evidence of their impact on individuals but may be influenced by underlying moral judgement about their nature and origin. The assignment of a higher disability weight to cannabis dependence than to autism is probably a reflection of a moral judgment. Also, it is quite likely that stigma plays a paradoxical part in the weighting of the disability associated with mental disorders given that acute schizophrenia was rated as being more disabling than blindness. Indeed, given the primacy of stigma to the disability associated with mental disorders (Alonso et al. Reference Alonso, Vilagut, Adroher, Chatterji, He, Andrade, Bromet, Bruffaerts, Fayyad, Florescu, de Girolamo, Gureje, Haro, Hinkov, Hu, Iwata, Lee, Levinson, Lépine, Matschinger, Medina-Mora, O'Neill, Hormel, Posada-Villa, Ismet Taib, Xavier and Kessler2013), it is unlikely that the method employed by the GBD 2010 could do justice to this aspect of the lived experience of those affected by the disorders. One way of ensuring that this will be the case in future GBD exercises is to attempt to capture this experience in the vignettes prepared for the assessment of disability weights. The use of vignettes of no more than 35 words in length as done for the GBD 2010 is unlikely to achieve this goal. Baxter et al. are correct in recommending further research that would help throw some light on the most effective way of capturing the complexity of health states, particularly those of mental and substance use disorders, in lay descriptions.