Indirect costs of sickness absence caused by mental and behavioural disorders (ICD-10: F00-F99) in Poland in the years 2012-2018

Introduction: Mental health is necessary for achieving the complete health by individuals. According to WHO, it is "a state of well-being in which every individual realizes his or her own potential, can cope with the normal stresses of life, can work productively and fruitfully, and is able to make a contribution to her or his community" (2). Unfortunately, there is an increasing number of people suffering from mental disorders that can deteriorate their life quality, lead to problems with the standard functioning in the society, a drop in productivity, and can cause disabilities.


Introduction
Mental health is a crucial element of health models, and its definition. The WHO defines the health as "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity" (1). Mental health is defined by the WHO as "a state of well-being in which every individual realizes his or her own potential, can cope with the normal stresses of life, can work productively and fruitfully, and is able to make a contribution to her or his community" (2). Accordingly, mental health is essential to individuals to achieve the complete health.
However, epidemiological studies demonstrate that more and more people are suffering from various types of mental disorders. According to the report of the Commissioner for Human Rights (3), 25-33% of the worldwide population is estimated to be affected by mental disorders. This proportion is said to be ca. 38% in European countries. Epidemiological studies performed in Poland indicate that more than 23% of the Polish population can be diagnosed with at least one mental disorder during their life, whereas ca. 20-30% of people aged 18-64 made complaints on reduced activity, mood disorders, oversensitivity or persistent fear.
The most common mental disorder includes anxiety disorders. It is estimated that 16-17% of the population suffers from such disorders. Further complaints are mood disorders (mainly depression) -ca. 10%, sleeplessness -7%, addictions -ca. 4%. Mental disorders in many cases deteriorate the life quality, cause problems with the standard functioning in the society, and result in a drop in productivity. They can also lead to infirmities. Neurological diseases and mental disorders are considered to be responsible for 25% of all reasons for infirmities.
The cited epidemiological data show that mental disorders are a serious health problem. Unfortunately, the analysis of the National Health Fund (NFZ) expenditures indicate that funds spent on mental health care in Poland are very low. In accordance with financial plans of NFZ (4-10), funds assigned to that purpose amount to 3.5% of all expenditures on health care (Table 1). In 2018, the amount of ca. 2.9 billion PLN was spent on mental health care and addiction treatment. It should be mentioned that such costs in financial plans of NFZ do not include costs of medicinal products.
In 2018, ZUS reported the issue of 19,948.5 thousand of medical certificates of temporary incapacity for work for the total number of 243,692 thousand days of sickness absence. It was more by ca. 18% than in 2012. The average duration of sickness absence in 2018 was 12.22 days and was shorter by 0.24 day compared to 2012. The number of absence days due to mental and behavioural disorders of people insured with ZUS was 19,424.8 thousand days in 2018 (ca. 39% more than in 2012) and accounted for ca. 8% of total days of sickness absence. The total number of reported medical certificates was 1,102.7 thousand of medical certificates (ca. 34% more than in 2012), and the average duration of sick leave was 17.62 days ( Table 2) (11)(12)(13)(14)(15)(16)(17).
Expenditures on sickness absences financed by the Social Insurance Fund (FUS) and funds of employing institutions were nearly 18.5 billion PLN. However, no data on costs of sickness absence by reasons in 2018 are available. Expenditures incurred in 2017 on sickness absence due to mental or behavioural disorders amounted to ca. 1.6 billion PLN, which accounted for ca. 9.5% of total expenditures (Table 3) (18)(19)(20)(21)(22)(23)(24).
Mental and behavioural disorders were the fifth reason for temporary incapacity for work in 2018 (Fig. 1). Wnioski: Zaprezentowany szacunek kosztów pośrednich może prowadzić do konkluzji, że opieka psychiatryczna w Polsce nie jest w najlepszej kondycji -koszty pośrednie mogą być dwukrotnie wyższe niż wydatki NFZ na opiekę psychiatryczną.    Apart from direct costs in the form of expenditures from NFZ and FUS, mental disorders also generate additional costs related to work incapacity and a drop in productivity of the sick, that is, indirect costs. Therefore, real effects of sickness do not only have an impact on a patient, but also on the economy as a whole. The estimation of indirect costs in economic analysis is very important to examine the impact of a specific illness or disease on all participants of the economic life from the macroeconomic perspective. A simplified impact of sickness on macroeconomic values and individual economic entities is presented in Figure 2.
Sickness [1] is a starting point if it has a direct effect (when a worker is on sick leave) or indirect effect (when a worker takes care of an ill person) on working people -the possibility of performing work duties is restricted in both cases. Sickness leads to a drop in labour force provided by households [2]. It results in reduced productivity of enterprises because, apart from the capital, work belongs to main productivity factors [3]. A drop in the number of hours worked generate lower incomes of households [4], which in turn reduces the consumption level [5]. All the above (a drop in incomes of households, reduced consumption and productivity) result in decreased revenues from taxes and contributions, and higher transfers paid by the state to households [7]. As a consequence, sickness deteriorates the situation of the public finances (25).
Indirect costs usually include: y a loss in production caused by sickness absence (absenteeism), y a drop in productivity caused by disease or illness of a worker present at work (presenteeism), y a loss in production caused by permanent incapacity for work, y a loss in production caused by the death, y costs of informal care, y labour costs for unpaid work,

Purpose of the article
The purpose of this article was an attempt to estimate indirect costs of sickness absence (absenteeism) caused by mental and behavioural disorders (ICD-10: F00-F99) in Poland in the years 2012-2018.

Materials and methods
Three methods of estimating indirect costs (lost production) are currently used: y human capital approach, y friction cost method, y willingness-to-pay method. The human capital approach was used for the purpose of this paper. It is the most common and frequently used method of estimating indirect costs of sickness (25,27) as it has been established in the economy theory and its use is relatively easy.
Economists define the human capital as "the source of professional knowledge, experience and skills accumulated by a worker during their education, training and practice, and the value of the worker is determined by opportunities created by the worker for gaining future incomes" (26). The capital of the person cannot be entirely used due to his or her sickness. And the human capital approach assumes that indirect costs caused by the sickness are generated during the whole period, during which the possibility of using the human capital of an individual is reduced (even when work duties of the sick are performed by another worker).
Indirect costs calculated with the human capital approach include: y production losses caused by the absence of a sick worker (absenteeism), y production losses caused by lower productivity of a sick worker present at work (presenteeism), y permanent incapacity for work, y the death as a result of the disease. Assuming the specific unit defining efficiency at work is required to estimate indirect costs, and consequently to determine production losses caused by sickness. The analysis of indirect costs does not contain the commonly used measure of efficiency due to problems resulting from reduced possibilities of measurements. No agreement on choosing the best measure can be found in papers on economics and pharmacoeconomics. EY researchers (25) indicated that the description of costs should be accompanied by the measure which: y is measurable and expressed in monetary units, y is understood and commonly accepted, y takes into account that work is not the only productivity factor, y takes into account that working people are only part of the population (there is unemployment). According to the literature review (25), researchers also indicated that the most common measures were: y GDP per capita/GDP per person employed, y added value per person employed, y remuneration (with or without contributions paid by employers to FUS).
A loss in the individual productivity was described in this paper using three indicators: y Gross Domestic Product per capita, y Gross Domestic Product per person employed, y corrected Gross Domestic Product per person employed (including corrected factor equal to 0.65 corresponding to the relation between the marginal and the average labour productivity adopted by the European Commission) (25,28). Table 4 shows demographical data and macroeconomic indicators used in estimating indirect costs of sickness absence due to mental disorders.
Indirect costs are the product of GDP per capita or per person employed or corrected GDP per person employed (Table 4) and the lost productivity over subsequent years (Table 5) estimated on the basis on data published by ZUS (11)(12)(13)(14)(15)(16)(17)   Source: compiled by the author on the basis of ZUS data (11)(12)(13)(14)(15)(16)(17).  Table 5). The number of years of sickness absence caused by mental disorders in 2018 was 53,219 and was greater by 39% than in 2012.  (Table 6). Specific illness or disease resulting in the longest duration of sickness absence contributed the most to indirect costs generated in the years 2012-2018 -in 2018 they were mental and behavioural disorders due to use of alcohol (F10), depressive episodes (F32), recurrent depressive disorder (F33), other anxiety disorders (F41), and reaction to severe stress, and adjustment disorders (F43) contributed to 76% of estimated indirect costs which amounted to 2.3-5.5 billion PLN (Table 7). Indirect costs generated by those five specific diseases increased by ca. 66%-88% in the years 2012-2018.

Conclusions
Indirect costs of mental disorders were estimated globally at 1.7 trillion US$ and were much higher than direct costs, which were estimated at 0.8 trillion US$ (based on data from 2010). For EU, indirect costs reached 798 billion EUR. It is expected that indirect costs will double by 2030 (36). In Australia lost gross domestic product as a result of Australians aged 45-46 exiting the labour force because of depression and other mental and behavioural disorders in 2015 was 6.67 billion AU$ (0,45 % GDP), of which 3.17 billion AU$ (0,21% GDP) were lost due to depression, and is going to increase to 9,8 billion AU$ in 2030 (4.33 billion AU$ due to depression) (37).
The estimation results indicate that indirect costs of sickness absence caused by mental and behavioural disorders (ICD-10: F00-F99) in Poland are very high -they were in the range of ca. 2.9-7.0 billion PLN in 2018 (the difference   paper which only describes the estimation of indirect costs of the sickness absence. Any estimation errors can be the result of not taking into account the economic cycle and the presence of its different phases -the amount of production losses was fluctuating depending on a downturn or an upturn in the economy. Thus, indirect costs could be overestimated in the boom stage of the cycle or underestimated in the slump stage. However, this criticism is not fully justified because the unit production value in the economy is not subjected only to economic fluctuations, but also to the growth trend. Thus, the elimination of recurring effects does not solve the fundamental issue related to the estimation of indirect costs, that is, a lack of "universal" measure for a specific disease, which is attributed to a specific time (e.g. month or year). Moreover, current amounts (not regularly corrected) of indirect costs inform decision-makers about the burden level at a specific moment.
The majority of faults in the human capital approach do not refer to the concept itself, but to imperfections of measures for production losses.
This analysis can lead to conclusions that indirect costs are the crucial element of the disease effects. An effort should be made to develop standards and guidelines to ensure the reliable estimation of indirect costs. More reliable calculations could encourage decision-makers to take real actions to reduce indirect costs, that is, to improve the health system.
Although the importance of indirect costs with reference to total costs generated by the disease has been acknowledged, there is no agreement on the need for including them into pharmacoeconomic analyses (38,39). It is probably caused by no formal requirements and no proper guidelines that would ensure their reliable evaluation (39).
The described estimation of indirect costs can lead to conclusions that underfunding of the mental health care in Poland results in a regular increase in the sickness absence, and thus in an increase in indirect costs of absenteeism due to mental and behavioural disorders.