Global Perspectives on Mental-Physical Comorbidity in the WHO Mental Health Surveys

Epidemiological data are the first step in estimating the impact of a health problem. Comorbidity of mental and physical disorders is a field that recently has been the focus of increasing attention. This book addresses this timely topic using epidemiological data regarding the main chronic physical conditions (pain, stroke, coronary artery disease, hypertension, diabetes, asthma, tuberculosis, chronic lung disease, parasitic disease, gastrointestinal ulcer, thyroid disease, neurological disorders, HIV infection, cancer) as well as psychiatric conditions, including depressive, anxiety, and substance use disorders. Importantly, the book presents data gathered using similar methodologies from 17 countries (10 developed countries, including the United States, and seven developing countries) in six continents in conjunction with the World Health Organization (WHO) World Mental Health Survey Initiative, and thus it gives the reader a truly global perspective. This book not only reports data, it has been written using a well-integrated observational and theoretical perspective. Using a stimulating approach to the concept of the “mind-body duality,” the authors try to answer questions about the relationship between the mind and body and their mutual influence as well as their relevance to health, disabilities, mortality, and social status. In summary, this book comprises a huge compilation of data from the most reliable surveys in the world. It can serve as a basis to generate hypotheses and devise clinical and public health solutions to improve the health of patients who suffer from these highly prevalent chronic mental and physical diseases.

The book is structured into the following four sections: 1) methodology and descriptive results, 2) risk factors and the role of childhood psychosocial adversities, 3) consequences of mental-physical comorbidity (including mortality), and 4) conclusions. The reader can find part of the material in this excellent book published in the highest impact journals covering mental health and epidemiology. The editors have improved and extended on the published data by including discussions regarding the implications of the findings, helping to put the entire data set, analyses, and derived conclusions into perspective. In addition, the reader should be aware of the close relationship that the current volume has with the book The WHO World Mental Health Surveys: Global Perspectives on the Epidemiology of Mental Disorders, which was commented upon in the Journal (1).

The book also notes that there are no specific patterns of physical-mental comorbidity and that the relationship between mental and physical disorders is more distal than proximal, even when comorbid conditions stem from a shared etiology or vulnerability. Mortality is a crucial but underappreciated issue in psychiatry (2). One likely barrier to decreasing this mortality is the stigma and discrimination that psychiatrically ill people, especially those with severe and persistent mental illnesses, encounter in general medical clinics. Finally, in Chapter 24, the authors develop a risk engine to estimate the mortality of comorbid conditions. The risk engine is an algorithm based on a statistical model from Dutch follow-up studies that can be used in databases from cross-sectional surveys. This risk engine could be used for better estimating prognosis for new surveys or even for calculating prognosis in single patients.

The limitations of the observational approach are those that are inherent to cross-sectional epidemiological surveys. In addition, several psychiatric conditions such as schizophrenia, bipolar disorders, and axis II disorders are excluded. Moreover, suicidal behavior, a principal cause of mortality in both mental and physical disorders, is not addressed in the chapters on mortality. Lifetime comorbidity is a subject of debate. Some authors consider that comorbidity in cross-sectional studies should be reported by age to avoid biased estimations (pseudocomorbidity) (3). This problem is addressed in the book by reporting results adjusted by country, gender, and age.

One of the most remarkable results is the evidence that mental-physical comorbidity rates are not different in developing countries relative to developed countries. Other studies have supported this view, with data showing that mortality patterns in developing countries are converging to those of developed countries (4). The authors point out the differences in healthcare system organization (primary and mental health) and accessibility to healthcare in these countries and interpret the results within this context. The final conclusion is that chronic conditions (physical and mental) are a challenge for societies and healthcare systems worldwide, for both developing and developed countries. The book provides the first step of evidence for general practitioners, psychiatrists, and policymakers to think, plan, and make decisions about problems more complex than the traditional public health problems such as infectious disease.