Global economic burden of schizophrenia: letter in response

Dear editor

In reference to the recent systematic review by Chong et al¹ on cost-of-illness studies in schizophrenia, we seek to highlight the limited scope and apparent inconsistencies embedded within this review. The review utilizes the term schizophrenia alone as the identifying disorder-related variable within its search strategy. Schizophrenia is the prototypical and most prevalent among the psychotic disorders, and schizophrenia is certainly used as a generic term in reference to the “schizophrenia-related disorders”, International Classification of Diseases (ICD)-10 codes F20–F29. The most well-known example of such use is in the Global Burden of Disease studies.^2–4 However, the reliance on this term as being all-inclusive is diminishing, as reflected in the chapter heading change from Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV to DSM-V, namely “Schizophrenia and Other Psychotic Disorders” to “Schizophrenia Spectrum and Other Psychotic Disorders”. Further, the overarching term psychotic disorders are increasingly being used in the recognition of the substantial clinical, neuropsychological, neuroimaging, and genetic overlap between disorders within this group.

Chong et al¹ review identifies one of our cost-of-illness studies pertaining to schizophrenia and other psychoses Carr et al,⁵ but not the other Neil et al⁶ which refers to psychotic disorders within its title and abstract. Regardless, both studies encompass equivalent populations, with the difference that some results are provided by major ICD-10 diagnostic category in the earlier study by Carr et al.⁵ As there is no reference to, or discussion of disease classifications, in either the determination of the search strategy or the populations included in the reviewed studies of Chong et al,¹ we are unable to comment on the comparability of the national cost comparisons made within the review.

In regard to the characterization of Carr et al⁵ within the review, we note the following qualifications. This analysis was primarily based on resource use assessed through interview of 980 individuals with psychosis, not through published literature, and with unit prices determined with reference to published literature. While the individuals were ascertained through a census of four urban locations, national prevalence was established, and national costs determined on this basis. Thus our paper of 2003 ought to have been incorporated in the national costs comparison, with estimates provided for both psychosis and schizophrenia (F20). As noted within the review, our study was one of the only three that considered total costs in relation to gross domestic product. We also noted that productivity losses due to suicide were separately estimated within the context of the analysis, although excluded from the total costs we presented.

Finally, we are uncertain as to what is encompassed by “direct nonmedical suicide related costs” in the study by Chong et al,¹ as suicide-related costs would normally be assessed as indirect costs. Furthermore, the inclusion of legal and law enforcement costs under indirect costs is not consistent with the usual definition which pertains, as specified by the authors, to productivity losses.