Employment and earnings trajectories before and after sickness absence due to major depressive disorder : a nationwide case–control study

This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details. Author(s): Title: Year: Version: Copyright: Rights: Rights url: Please cite the original version: CC BY-NC 4.0 https://creativecommons.org/licenses/by-nc/4.0/ Employment and earnings trajectories before and after sickness absence due to major depressive disorder : a nationwide case–control study © Authors, 2020 Accepted version (Final draft) Hakulinen, Christian; Böckerman, Petri; Pulkki-Råback, Laura; Virtanen, Marianna; Elovainio, Marko Hakulinen, C., Böckerman, P., Pulkki-Råback, L., Virtanen, M., & Elovainio, M. (2021). Employment and earnings trajectories before and after sickness absence due to major depressive disorder : a nationwide case–control study. Occupational and Environmental Medicine, 78(3), 173-178. https://doi.org/10.1136/oemed-2020-106660 2021 RUNNING HEAD: SES TRAJECTORIES AND DEPRESSION Employment and earnings trajectories before and after sickness absence due to major depressive disorder: a nationwide case-control study Christian Hakulinen1,2*, Petri Böckerman3,4,5, Laura Pulkki-Råback1,6, Marianna Virtanen7,8, Marko Elovainio2,9 1Department of Psychology and Logopedics, University of Helsinki, Helsinki, Finland 2Finnish Institute for Health and Welfare, Helsinki, Finland 3School of Business and Economics, University of Jyväskylä, Jyväskylä, Finland 4Labour Institute for Economic Research, Helsinki, Finland 5IZA (Institute for the Study of Labor), Germany 6Department of Child Psychiatry, University of Turku, Turku, Finland 7School of Educational Sciences and Psychology, University of Eastern Finland, Joensuu, Finland 8Division of Insurance Medicine, Karolinska Institutet, Stockholm, Sweden 9Research Program Unit, Faculty of Medicine, University of Helsinki, Helsinki, Finland Corresponding author: Christian Hakulinen, University of Helsinki, P.O. Box 21, 00014, Helsinki, Finland. Tel: +358 50 448 2041 Email: [email protected] Word count: 3034 words in the main text; 246 words in the abstract; 1 table; 4 figures; online supplementary appendix (4 figures) SES TRAJECTORIES AND DEPRESSION 2 Objectives: To examine employment and earnings trajectories before and after the first sickness absence period due to major depressive disorder (MDD). Methods: All individuals (n=158 813) in Finland who had a first sickness absence period (lasting longer than 9 days) due to MDD between 2005 and 2015 were matched with one randomly selected individual of the same age and gender with no history of MDD. Employment status and earnings were measured using register-based data annually from 2005 to 2015. Generalized estimating equations were used to examine the trajectories of employment and earnings before and after MDD diagnosis in men and women separately. Results: Sickness absence due to MDD was associated with increased probability of nonemployment during and after the year of the first sickness absence period. In men, but not in women, the probability of being employed was lower five years before the sickness absence period due to MDD. When compared to the individuals in the control group, men had around 34% and women 15% lower earnings one year, and 40% and 23%, respectively, five years, after the first sickness absence period due to MDD. More severe MDD and longer duration of sickness absence period were associated with lower probability of being employed. Conclusions: Sickness absence due to MDD is associated with considerable reduction in employment and earnings losses. For men and individuals with more severe MDD, this reduction was before the first sickness period. This supports a reciprocal association between employment and earnings with MDD. Keywords: depression; sickness absence; socioeconomic position; trajectories; register-based research SES TRAJECTORIES AND DEPRESSION 3 What is already known about this subject? • Whereas reciprocal association between depression with employment and personal income have been found in previous studies, employment and income trajectories before and after the first sickness absence due to MDD have not been examined. What are the new findings? • Sickness absence due to MDD is associated with considerable reduction in employment and personal income losses. • Among men and in those with more severe depression, labour market and economic disadvantage was prevalent years before the first sickness absence due to MDD. How might this impact on policy or clinical practice in the foreseeable future? • The present findings highlight the need for effective clinical practices and policies to reduce the burden of depression in the working-age population. SES TRAJECTORIES AND DEPRESSION 4 Major depressive disorder (MDD), which we sometimes refer to as “depression”, is a leading cause of disability around the world, and it is associated with tremendous social and economic burden1. Cost-of-illness studies have documented that unemployment and reduced productivity due to depression constitute the largest financial costs of the total indirect costs associated with depression1–3. Consistent with this evidence, most prospective observational longitudinal cohort studies have shown that major depressive disorder, depression-related sickness absence, or high number of depressive symptoms are associated with socioeconomic outcomes in terms of unemployment and low income4–12. This suggests that depression could lead to a low socioeconomic position (SEP) over the life course (i.e., health selection), and to a reduced worklife expectancy13. On the other hand, low SEP has been associated with increased risk of depression14–20, also in studies where the history of depression or other mental disorders have been taken into account17, indicating that socioeconomic adversity is a likely cause of depression (i.e., social causation). However, there is a lack of nationwide studies examining how MDD is related to trajectories of employment and personal income. This issue is of high policy importance as for a significant fraction of all affected individuals, depression seems to be a rather transient condition21,22. For example, half of the individuals with MDD have been found to recover within 6 months23, and most individuals diagnosed with MDD receive treatment only up to 2 years24. While depression and severe psychological distress have been associated with an increased risk of sickness absence25–27, a large-scale study of Finnish public-sector employees showed that over 85% of depression-related work absence episodes ended as the person returned to work28. In a recent study using data from a a nationally representative panel survey from Australia29, severe self-reported depressive symptoms were associated with unemployment, but unemployment had only a marginal effect on severe depressive symptoms in women, but not in men. To summarize, whereas it is likely that MDD is associated with unemployment and reduced income, it remains unclear what is the quantitative magnitude of SES TRAJECTORIES AND DEPRESSION 5 the ‘scarring’ effect of MDD on socioeconomic outcomes and whether reduced levels of employment or income are present already before the depression diagnosis. The aim of the present study was to examine employment and earnings trajectories before and after the first sickness absence period due to MDD using nationwide register-based data from Finland. We investigated: (a) the average reduction in the employment rate and earnings in individuals after the onset of first recorded sickness absence due to MDD, (b) whether individuals with sickness absence due to MDD have lower employment rate and earnings before the first MDD-related sickness absence, (c) whether the association between MDD and employment differs according to the severity of MDD and duration of sickness absence related to MDD, (d) whether associations were similar in all educational groups. The heterogeneity analysis is important because high education may protect individuals from loss of earnings30. Depression diagnoses and reporting of depressive symptoms are more common in women than in men 31, although previous studies have provided mixed empirical findings whether the association between MDD and socioeconomic factors differs between men and women29,32,33. For this reason, the associations for men and women were analyzed separately. Methods Study design and setting Using personal identity numbers, which have been assigned to all Finnish residents starting from 1969, the study population was constructed by linking the following nationwide registries: population registry of Statistics Finland, the Causes of Death Statistics of Statistics Finland, and the sickness allowance register of the Social Insurance Institution of Finland (Kela). The population registry of Statistics Finland contains information on general demographics and individuals’ labour market status, including salaries extracted from tax SES TRAJECTORIES AND DEPRESSION 6 registers. The Causes of Death Statistics of Statistics Finland contains the date and cause of death. The sickness allowance register maintains administrative information on sickness absences that were granted due to MDD and that were longer than nine days. The cut-off at nine days is based on the institutional structure of the Finnish sickness insurance system34. After the 9‐day waiting period the employee is eligible to receive an earnings‐ related sickness allowance from Kela that also keeps a record of the spells of sickness absence. Individuals who are aged between 16 to 67 years and cannot do regular work because of their illness are eligible for the sickness allowance. Persons who are not employed can also apply, and also persons who are on temporary or permanent pension if they have been working. The sickness allowance has no ceiling and on average 70% of the previous earnings are covered by the sickness allowance34. Information on sickness absences was available from 2004 to 2015. The length of sickness absence was measured in days. Study population Individuals (n=158 813; 64% women) who were born between 1942 and 1997, who had their recorded sickness absence spell (lasting more than 9 days) due to MDD between 2005 and 2015, and who were alive and living in Finland during the year the first sickness absence due to MDD was given constituted the study population of cases. Individuals who received a sickness absence due to MDD in 2004 were excluded. Each case (i.e., an individual with the first recorded sickness absence spell due to MDD between 2005-2015) was matched to one randomly selected control individual of the same birth year, birth month, and gender, who did not have a sickness absence due to MDD before or during the year of the case. Ethical permission SES TRAJECTORIES AND DEPRESSION 7 The ethics committee of the Finnish Institute of Health and Welfare (THL/730/6.02.01/2018) approved the study. Data were linked with the permission of the Statistics Finland (TK-531696-16), the National Institute of Health and Welfare, and the Social Insurance Institution of Finland. Assessment of MDD-related sickness absence MDD-related sickness absence was diagnosed by a physician (i.e., general physicians, occupational physicians and psychiatrists) using the ICD-10 code F32. Mild or moderate MDD (ICD-10 codes F320-F321) and severe MDD (ICD-10 codes F322-F323) were also defined. Assessment of employment and earnings Annual employment status was measured as the employment status during the last week of each calendar year. Individuals who were wage and salary earners or self-employed were defined as employed. All others were classified as non-employed. The total level of earnings, which include wage and salary earnings and self-employment income, were measured annually, i.e., each year. To ensure the comparability of income measures over the observation period, earnings were deflated to the base year 2015 using the official consumer price index maintained by Statistics Finland. Covariates Education was measured at the time when MDD was diagnosed in cases and during the corresponding year among individuals in the control group. Education was classified as follows: 0=primary education (i.e., only basic compulsory education); 1=secondary education (i.e., completed upper secondary education or similar); 2=higher education (i.e., completed at least bachelor’s degree, master’s degree, polytechnic degree or similar). SES TRAJECTORIES AND DEPRESSION 8 Statistical analyses The observation period started at the year of the first sickness absence due to MDD for cases (i.e., those individuals who received a MDD diagnosis) and at the matched year for the control individuals. Participants were then followed backward and forward for as many years they had data available up to the maximum of 10 years (i.e., years 2005 to 2015). Thus, participants who were diagnosed with MDD at the beginning of the study period (e.g., year 2005), contributed mostly to the data after the first sickness absence period due to MDD, and the participants who were diagnosed with MDD at the end of the study period (e.g., year 2015), contributed mostly to the data before the first sickness absence period due to MDD. Generalized estimating equations (GEE) were used to examine the trajectories of employment and earnings before and after sickness absence due to MDD. GEE allowed to account for correlations among repeated observations (i.e., employment and earnings) contributed by a single participant. With employment, logic link-function and binomial family function were used, and with earnings, log link-function and poisson family function were used. Employment (1=employed vs. 0=not employed) and annual earnings in euros were used as outcomes. Case status (1=case; 0=control), time point, age-groups in five-year intervals, and interaction between case status and time point were used as predictors. To examine whether the trajectories of employment and earnings varied by the severity of the MDD diagnosis (0=not specified; 1=mild or moderate; 2=severe) and the length of sickness absence, additional models were examined only among cases. The length of sickness absence was transformed from the number of days to quartiles (Q1=shortest; Q4=longest). In addition to reporting results using relative effect sizes, margins command in Stata was used to calculate covariate adjusted predictions. Stata 15.1 (Stata Corp, College Station, TX) was used in all analyses. SES TRAJECTORIES AND DEPRESSION 15 REFERENCES 1. Greenberg PE, Fournier A-A, Sisitsky T, Pike CT, Kessler RC. 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Scand J Work Environ Heal. 2019;45(4):324-332. doi:10.5271/sjweh.3791 SES TRAJECTORIES AND DEPRESSION 20 Figure captions Figure 1. Predicted trajectories of employment in men and women with and without sickness absence due to MDD. Note. Year 0 depicts the year of MDD diagnosis. Figure 2. Predicted trajectories of personal earnings for men and women with and without sickness absence due to MDD. Note. Year 0 depicts the year of MDD diagnosis. Figure 3. Predicted trajectories of employment for men and women with and without sickness absence due to MDD according to educational level (primary, secondary, higher) Note. Year 0 depicts the year of MDD diagnosis. Figure 4. Predicted trajectories of employment according to the duration of sickness absence (Q1=shortest, Q4=longest) due to MDD (A-B) and severity of the MDD (C-D) Note. Year 0 depicts the year of MDD diagnosis. SES TRAJECTORIES AND DEPRESSION 21 Table 1. Descriptive statistics of the study sample Men (n=56 472) Women (n=102 341) Not case Case Not case Case Age in years 40.9 (12) 40.9 (12) 40.9 (12.2) 40.9 (12.2) Employed 74.6% 67.4% 74.1% 75.3% Earnings in euros 36 800 (49 300) 31 700 (44 500) 26 800 (37 500) 26 700 (18 400) Education Primary 21.7% 25.8% 16.7% 18.9% Secondary 58.9% 59.8% 58.9% 62.3% Higher 19.4% 14.4% 24.2% 18.8% Severity of depression Not specified - 69.3% - 70.8% Mild or moderate - 21.6% - 22.3% Severe - 9.2% - 6.9% Duration of sickness absence in days - 65 (79) - 54 (71) Note. Values are means (and standard deviations) or percentages