The Global Burden of Disease, Injuries, and Risk Factors Study (the GBD study), led by Murray and Lopez, was initially conducted in 1990.1 This study was the first large-scale, systematic effort to provide a comparable assessment of health loss due to diseases and injuries at both global and regional levels. In the GBD framework, the summary measure of disease burden is the disability-adjusted life-year (DALYs), which sums years of life lost due to premature mortality (YLLs) and years lived with disability (YLDs) due to a particular disease.2 One DALY represents the loss of 1 year of full health. By combining YLLs and YLDs, DALYs facilitated the comparison of the burden of diseases and injuries that cause early death as well as those that cause disability, an approach that was ground-breaking in that it was able for the first time to highlight neuropsychiatric disorders (a disease category including neurological, mental and substance-use disorders) as leading causes of disease burden.

Notable key findings emerging from the 1990 study were that neuropsychiatric disorders accounted for more than 25% of global YLDs with 5 of the top 10 causes of disability included within the neuropsychiatric category (unipolar major depression, alcohol use, bipolar disorder, schizophrenia and obsessive–compulsive disorders). Depression was the leading cause of YLDs while dementia was associated with high rates of both YLDs and YLLs.3–6

Investigations of prevalence within Europe also highlight mental and neurological disorders as a highly impacting group of disorders.7–10 For instance, in Spain, data from the EseMed study reported a lifetime prevalence of mental disorders of 19.5%.7 According to the National Institute of Statistics,11 neurological disorders were the fourth leading cause of death in Spain for 2012. Murray and colleagues estimated that, in 2020, the overall proportion of neuropsychiatric disorders will be 14.7% worldwide.4 Similarly, the World Health Organisation estimated an increase of 15%,12 although in both instances, estimates were derived using data projections from previous years.

In 2007, a new Global Burden of Disease study (GBD 2010) was carried out and published in late 2012. Remarkable improvements in methodology were introduced to overcome limitations from the previous 1990 study, such as the use of population-based surveys to calculate disability weights which had been previously derived from expert consensus and the estimation of 95% uncertainty around all burden estimates.13 GBD 2010 also expanded on the set of neuropsychiatric disorders investigated. New categories (e.g. pervasive developmental disorders, childhood behavioural disorders) were included and existing categories were expanded (e.g., unipolar depression was divided into major depressive disorder and dysthymia; drug use disorders were divided into cocaine, cannabis, opioid and amphetamine dependence). Changes in methodology between the 1990 GBD study and its most recent iteration (GBD 2010) have been summarised in greater detail elsewhere.6,14,15 As these changes in methodology invalidated any comparison of burden estimates between the two studies, GBD 2010 estimated burden for both 1990 and 2010 to facilitate the investigation of burden across time.16

GBD 2010 findings highlighted that nine of the top 20 causes of disability were included within the neuropsychiatric category (e.g. depression, anxiety disorders, migraine, drug use disorders). Shifts in population growth and ageing due to increases in life expectancy also meant that more of the world's population were living to the age when neuropsychiatric disorders are most prevalent.14,17 Although GBD 2010 global findings for neuropsychiatric disorders has been previously reported,6,14 it is also important to present on the trends in burden at a national level. Knowledge of differences in burden at the country level is needed for priority setting in national health agendas and the development of health policies that address age, sex and year specific trends in burden and their impact on national health systems.

In this paper, we aim to report on the burden of neuropsychiatric disorders in Spain, for 1990 and 2010. To the best of our knowledge, this is the first study reporting on the burden of neuropsychiatric disorders in Spain using data from the GBD 2010 study.

The GBD 2010 study involved a comprehensive assessment of burden for 291 diseases and injuries, and 67 risk factors for 20 age groups in 187 countries distributed across 21 world regions.2,13–15 Burden was assessed in terms of YLLs, YLDs and DALYs. Information about GBD 2010 definitions and methods will be briefly summarised here as they have been described in detail elsewhere.13–15

In this paper, Spanish outcomes with respect to neuropsychiatric disorders are presented. Neuropsychiatric disorders were made up of neurological, mental and substance-use disorders, defined using the Diagnostic and Statistical Manual of Mental Disorders18 and the International Classification of Diseases.19 More specifically, neurological disorders included: Alzheimer's disease and others dementias, Parkinson's disease, epilepsy, multiple sclerosis, migraine, tension-type headache. Mental and substance-use disorders were made up of schizophrenia, alcohol, opioid, cocaine, amphetamine, and cannabis dependence, depressive disorders (major depressive disorder and dysthymia), bipolar disorder, anxiety disorders, eating disorders, pervasive developmental disorders (autism, Asperger's syndrome), childhood behavioural disorders (attention-deficit hyperactivity disorder, conduct disorder), idiopathic intellectual disability; and for disorders for which there was insufficient data to be assessed individually, three residual groups of other neuropsychiatric disorders were included.14

In spite of the low contribution of neuropsychiatric disorders to global YLLs, this group of disorders was the most disabling, accounting for 30.7% of total YLDs in Spain in 2010. Overall, most neuropsychiatric disorders increased in burden between 1990 and 2010. This increase was driven by changes population growth and ageing and in some instances (e.g. for substance-use disorders) increases in the prevalence rate. Depressive disorders were the most disabling of the neuropsychiatric disorders due to the high prevalence and disability weight associated with major depressive disorder.6 Nevertheless, it is important to note that, as illustrated by Whiteford and colleagues, other neuropsychiatric disorders such as schizophrenia and Parkinson's disease were ranked with a high disability weight in GBD 2010 but accounted for a lower percentage of YLDs and DALYs because their prevalences were lower.6,24

The burden of neuropsychiatric disorders varied across the lifespan. Burden was high in young adults and the elderly. The high proportion of burden due to neuropsychiatric disorders in young adults could be explained in some cases by an early onset of disorders associated with a high prevalence such as substance-use disorders, anxiety disorders and depressive disorders. The results also showed a high proportion of burden due to neurological disorders in the elderly. This was largely explained by the increase in the prevalence of highly disabling neurological disorders such as Alzheimer's disease or Parkinson's disease. As the population ages due to increases in life expectancy, it is expected that burden of diseases occurring in the elderly will also increase making neuropsychiatric disorders an important target for both the current and future health of the Spanish population.25

Significant differences were found when comparing Spanish data with global results. In 2010, neuropsychiatric disorders accounted for 10.4% of all DALYs worldwide, and 15.4% in developed countries,15 whereas in the Spanish population the figure was 18.4%. Although trends are similar in Spain and globally over the years, neuropsychiatric disorders make a larger contribution to disease burden in Spain.

Concerning the burden of disease in other European countries, we observed that, overall, the burden attributable to neuropsychiatric disorders was similar as well. All neuropsychiatric diseases included in the top 20 causes of DALYs increased their percentage contribution from 1990. Indeed, depression was the most disabling disorder among neuropsychiatric disorders in countries such as France, the United Kingdom, Germany and Italy, ranking between third and seventh position in terms of absolute DALYs. Other disorders, which were also among the 20 leading causes of DALYs in France, the United Kingdom, Germany and Italy, were Alzheimer's disease, drug-use disorder, migraine, anxiety disorders or alcohol-use disorder, with varying percentages.26–29

Findings from GBD 2010 are in line with findings from previous epidemiological studies that have demonstrated the high impact of neuropsychiatric disorders in the population.8,10 For instance, the ESEMeD study reported a high prevalence of mental disorders in Spain, particularly depression.7 Separate analyses of burden in Spain have also highlighted the impact of neuropsychiatric disorders, although there were differences in the methodology used to estimate burden. These studies also emphasised neuropsychiatric disorders as a leading contributor of total DALYs, especially for women and those ages between 15 and 30 years of age.30,31 Similarly, dementia was also highlighted as a major contributor of disease burden in the elderly.32 Research focused on the Valencia and Andalusia regions of Spain obtained comparable results.33,34

In spite of these findings, the direct and indirect costs of neuropsychiatric disorders are inadequately covered in most countries.35 The budget set for neuropsychiatric disorders in Spain represents less than 10% of public health expenditure36 and not in line with our results which highlight neuropsychiatric disorders as a leading contributor to disability. Our findings underline the importance of prioritising neuropsychiatric disorders in the national health policies and allocating resources towards their prevention and management.

Despite the progress made compared with previous GBD studies, we need to consider the limitations associated with GBD 2010 while interpreting findings. First, as the number of disorders included was limited, the burden of neuropsychiatric disorders may have been underestimated. Disorders were included if there was sufficient data to derive defensible estimates of burden. As such, disorders such as personality disorders, somatoform disorders and substance-abuse were not included.

Second, neuropsychiatric disorders were defined according to DSM and ICD guidelines which may not capture all presentations of the disorders. However, this was necessary to facilitate the comparison of epidemiological data and burden estimates between settings. Future work on burden of disease will have to explore how recent changes to these guidelines (for instance, the changes proposed in the latest iteration of DSM) will impact on the estimated burden of neuropsychiatric disorders in Spain. Third, neuropsychiatric disorders contributed to a much smaller proportion of YLLs compared to YLDs. The ICD-10 guidelines used in GBD 2010s cause of death allocations can only attribute deaths to the direct (rather than the underlying) cause. As such, deaths due to neuropsychiatric were allocated to other causes in GBD 2010 (e.g. suicide related deaths due to having a mental disorder allocated to injuries).9,22,37

Fourth, was the non-inclusion of social consequences in estimating disability weights. The impact of neuropsychiatric disorders on functioning and society at large, although well publicised was not considered.38,39 Finally, although 95% uncertainty intervals were presented for all high level findings in GBD 2010, given the lack of data available on the epidemiology of neuropsychiatric disorders, uncertainty intervals were often large and overlapping. This needs to be considered while interpreting findings. With ongoing epidemiological research and updates of GBD estimates, we aim to be able to reduce the unexplained sources of uncertainty around estimates of burden for neuropsychiatric disorders.

This study contributes to understanding of the burden of neuropsychiatric disorders in Spain and demonstrates that they should be considered an integral component of the public health system. Findings highlight the urgent need for health policy focusing on the development of effective and affordable approaches to reducing the existing burden of neuropsychiatric disorders in Spain and prevention programmes to reduce incident-cases of these disorders in the population. That said, more epidemiological research is needed for a better understanding of burden. Future studies should also consider the contribution of social and economic determinants to the burden of neuropsychiatric disorders.

This study has been supported by Bill & Melinda Gates Foundation. This study was done as part of GBD 2010.

The authors declare that they have no conflict of interests.