There have been few epidemiological studies on recurrent sickness absence due to depression after returning to work (RTW). The objective of this study was to investigate the prognosis of workers who are RTW with depression in a Japanese company. This study employed a descriptive epidemiology study design. Subjects of this study were 540 employees who worked full-time and were registered in the Health Data System and returned to work from April 2002 to March 2008 after their first leave of absence due to depression. We investigated the recurrence of sickness absence due to depression after returning to work using the Kaplan-Meier survival curve method. During the 8.5 yr follow-up period, almost half of the RTW employees experienced recurrent sickness absence. There was a steep increase in recurrent rates the first two years after RTW, and 85.2% of total recurrence of sickness absence had occurred within three years after the index episode.

Depression is a serious illness with a high recurrence rate, mortality, and suicide rate and a substantial loss of quality of life¹⁾. In recent papers, depression is recognized as important problems in developed countries^2,3,4,5,6). Depression is one of the most important risk factors for suicide⁷⁾. Especially in Japan, the number of suicides has increased rapidly over the last several decades, to over 30,000 in 1998 and has remained to the present⁷⁾. According to the National Police Agency survey, 8,997 Japanese employees committed suicide in 2008⁸⁾. Sickness absence due to depression has become an important occupational health problem with serious consequences for individuals as well as companies⁹⁾. Workplace costs per depressed individual amounted to $3,032, which are the single largest category¹⁰⁾. Depression imposes a substantial economic burden on Japanese society¹⁰⁾.

There have been some studies on the incidence of sickness absence due to depression recently^{9, 11,12,13,14)}. There was no difference between female and male employees in the frequency of absence due to depression in Japanese survey²⁾. Women had a higher risk of long-term (>8 wk) sickness absence with depression than men in Norway survey⁹⁾. In Norway, sickness absence with depression increased between 1994 and 2000¹⁴⁾. Depression is a long-lasting predictor of onset, duration and recurrence of sickness absence¹¹⁾.

In Japan, especially for tertiary prevention of occupational mental health, many Japanese companies have been introducing various return-to-work (RTW) systems recently, from the guidelines of RTW principles from the Ministry of Health, Labor and Welfare 2004 or psychiatric experts’ opinions¹⁵⁾. These include an RTW committee, reduced working time, and regular follow-up interview by occupational health staffs. Although RTW is generally considered to be directly related to recovery, the situation is usually more complex, because varying levels of symptom severity are loosely associated with patterns of sickness absence and work disability¹⁶⁾. Recurrences after recovery from depression represent important problems for companies, employees, and occupational health staff¹⁷⁾, because employees who returned to work after sickness absence due to depression are at increased risk of recurrent sickness absence¹⁸⁾.

It seems that there has been more interest in follow-up for employees who returned to work after sickness absence due to depression in Japan¹⁵⁾.

There have been few epidemiological studies on recurrent sickness absence due to depression after RTW^{18, 19)}. It is very important to predict when recurrent sickness absence due to depression will occur, because by knowing when recurrence will occur, occupational health staffs could know until when they should follow up RTW employees. The objective of this study was to investigate the prognosis of workers who RTW with depression in a Japanese company.

This study employed a descriptive epidemiology study design.

Company A investigated in this study is one of the biggest data communication companies in Japan and is involved in various fields; regional and international telecommunication services (installing and maintaining telephones, faxes, telegrams, internet systems etc).

The sickness absence system in company A is as follows; employees who are not working well or are suspected of having a mental disorder are recommended to see a psychiatrist early and to rest, by their immediate superior or occupational health staff.

Their immediate superiors ask them to submit a psychiatrist’s certificate to be certified for sickness absence. An employee with depression has to submit a psychiatrist’s certificate (archives) which says “this employee needs to rest.” Certificates from psychiatrists can be admitted for sickness absence due to depression. His or her immediate superior receives the document and sends a copy to the occupational health center. After confirming the name of the employee, the diagnosis, the comment from the psychiatrist that the employee needs to rest, and the duration of sickness absence on the certificate, the occupational physician (OP) registers this information in the Health Data System of this company. If an employee is taking their first sickness absence due to depression, the OP registers it as “first leave” according to company regulations.

Sickness absence in company A is of two types; “byokikyuka” (means short sickness absence: BY), and “kyusyoku” (means long sickness absence: KY), according to human resources regulations. Employees who submit a psychiatrist certificate are registered as BY. When the duration of sickness absence exceeds the human resource standard, the employee is registered as KY. The human resource standard which should be regarded as KY is 3 months for 0–9 yr duration of employment, 6 months for 10–19 yr, and 1 yr for 20 yr, respectively.

Regarding the process of RTW, firstly, employees must submit their psychiatrist’s certificate which says, for example “this person can return to work from December 24”. After submitting the certificate for RTW, employees need to have an occupational physician interview. As a rule, the employee, the immediate superior, and the OP attend the interview for work adjustment. An employee with BY can return to work after the OP interview. An employee with KY needs to be judged by the RTW committee twice. The first RTW committee judges whether an employee with a psychiatric disorder can work during the observation period, usually 3 months. Based on the OP’s and superior’s report of the situation during the observation period, such as attendance, appearance, motivation for RTW, attitude to job, interpersonal relationships with superiors and colleague, endurance for job and so on, the second committee can judge whether this employee can return to work. After passing this committee twice, employees can return to work. The definition of the RTW day is the day when OPs decide as appropriate as for employees’ RTW after OP interview or RTW committee.

Recurrent sickness absence due to depression is also defined only by a psychiatrist’s certificate.

The number of employees who worked for this company on a full-time basis from 2002 to 2010 was about 68,000. Of these employees, subjects were collected from the company register, searching for all employees who satisfied both inclusion and exclusion criteria. Employees who were registered in the Health Data System and returned to work from April 1, 2002 to March 31, 2008 after their first sickness absence due to depression (F3; ICD-10, based on a psychiatrist’s certificate) were included.

This criterion meant that this study population did not include employees who had had previous episodes of psychiatric disorder before April 1, 2002, and employees who were absent because of schizophrenia, anxiety disorder, eating disorder, adjustment disorder, alcohol dependency and other mental disorder except F3 (ICD-10).

Of the employees who filled the inclusion criteria, we excluded employees who satisfied the following exclusion criteria:

-KY employees, because the criteria for RTW differs between BY employees and KY employees.

-employees whose data for the day at loss to follow-up were totally unknown after returning to work (for the Kaplan-Meier survival curve, we needed to know the day at loss to follow-up, such as the day of being transferred, registering, sickness absence due to other diseases).

-employees who were diagnosed with maniac disorder by a psychiatrist’s certificate.

-employees who had other factors that caused secondary depression, such as interferon therapy for hepatitis C or post-partum depression before April 1, 2002.

Figure 1 shows the pathway to RTW in this study population. First of all, 614 employees submitted a psychiatrist’s certificate from April 1, 2002 to March 31, 2008. Of the 614 employees, 74 were excluded: 55 who were KY employees, 17 whose data for the day at loss to follow-up were totally unknown after RTW, 2 who had had other factors causing secondary depression, such as interferon therapy for hepatitis C or post-partum depression. We regarded 540 employees as the study population for analysis.

Fig. 1.

The pathway to RTW in this company and study population. BY: short sickness absence. KY: long sickness absence. Employees who submit a psychiatrist certificate are first registered as BY. When the duration of sickness absence exceeds the human resource standard, the employee is registered as KY. The human resource standard line which should be regarded as KY is 3 months for 0–9 yr’ duration of employment, 6 months for 10–19 yr, and 1 yr for 20 yr, respectively.

The period of sustaining working without relapses was expressed by using Kaplan-Meier survival curves. The starting day of the well interval was the day of RTW after the index episode in the Health Data System. The ending day of the well interval was the first day of recurrent sickness absence due to depression certified by psychiatrists, or the day of censoring: the day of follow-up (September 30, 2010), the day of resigning, the day of being transferred to another company, the day of maternity leave, or the day of sickness absence due to other diseases except depression certified by physicians, such as malignancy, hernia, gastric ulcer and so on.

We collected the data of whether the study population had recurrent sickness absence due to depression since the day of RTW to September 30, 2010. After RTW, 35 employees were censored: 2 due to lumber disk hernia, 3 due to maternity leave, 11 transferred to other companies, 14 resigned, 1 due to alcoholism, 1 due to ischemic heart disease, and 3 due to benign or malignant disease during the 8.5 yr follow-up period. These 35 employees were analyzed from the day of RTW to the censored day.

The Kaplan-Meier survival curve for recurrent sickness absence was used, and recurrence rates were calculated. The proportion of recurrent sickness absence in each period after RTW was shown as follows.

It is useful to examine recurrence of sickness absence in different time periods after RTW, because it is expected for us to know how long occupational health professionals should follow up RTW employees. Data were analyzed using IBM SPSS ver.19.0 software for Windows.

This study was approved by the Medical Ethics Committee of Dokkyo Medical University.

The basic characteristics of the participants are shown in Table 1. The total population was 540 employees, 455 male (84.3%). Mean age was about 41 yr old, and the duration of employment was about 20 yr. The duration of the first sickness absence due to depression was about 3 months.

During the follow-up period, 36 women (42.4%) and 199 men (43.7%) experienced recurrent sickness absence. The cumulative recurrent rate for the total study population was shown in Table 2.

The Kaplan-Meier survival curve for recurrent sickness absence was shown in Fig. 2.As visualized in Fig. 2, there was a steep increase in recurrent rates the first two years after RTW, and 85.2% of total recurrence of sickness absence had occurred within three years after the index episode. Recurrent sickness absence was, however, evident as long as 8 yr after the index episode and by the end of follow-up, almost half of the employees (49.3%) had experienced recurrent sickness absence.

Fig. 2.

Cumulative recurrence rates by Kaplan-Meier estimate (total population).

In occupational health, there have been few studies on the prognosis of employees with depression using survival analysis. To our knowledge, this is the first study to show the recurrence rate of sickness absence due to depression after RTW, showing that about 50% RTW employees had recurrent sickness absence during the 8.5 year follow up period and most of the recurrences were concentrated in the three years after RTW.

This study was in line with previous clinical studies reporting that mental disorders have high recurrence rates^20,21,22,23).

This result showed there were no gender differences in recurrence of depression, in line with other studies^{17, 18, 20)}.

In the field of psychiatry, there have been many studies into recurrence after recovery for common mental disorders using survival analysis^{1, 20,21,22,23,24,25,26)}. Compared with previous studies, the recurrence rate among our study population was much better than in these hospital patient studies^20,21,22).

As compared with general population studies, our recurrent curve after RTW was slightly worse^{1, 24, 26)}. It is not generally so easy for patients with depression to keep working after RTW. That may affect the differences of the recurrent rates after recovery.

To our knowledge, only one study, the Dutch Post and Telecom study, has investigated recurrence after sickness absence due to depression in a working population¹⁹⁾. The results of the present study were similar, reporting that 48% of employees with sickness absence due to depression at baseline had recurrent episodes during 4 yr follow-up¹⁹⁾. As it is known that RTW employees often are not fully recovered from their depressive symptoms²⁷⁾, depression may be associated with recurrent sickness absence.

However, the present study has not examined recurrence rates of mental disorders, but rather recurrence rates of sickness absence due to depression, which is a functional outcome of depression. Sickness absence is a complex and multi-causal phenomenon, and there is no unified theory or consensus regarding the impact of depression on recurrence of sickness absence¹¹⁾. This study in occupational health is quite difficult to compare to studies in the field of psychiatry. And studies on the prognosis of depression are difficult to compare due to differences in methodology²⁸⁾. In order to analyze the prognosis of employees with depression after RTW, further epidemiological studies will be needed, especially for occupational health.

Referring to the Kaplan-Meier recurrence curve in this retrospective cohort, the incidence of recurrent sickness absence declined over the years after RTW; recurrence was concentrated most frequently in the first year, followed by the second year. This tendency was in line with previous studies^{19, 21)}. Based on the results of this study, relapse prevention consultations are recommended for at most 5 yr, while other studies recommended for a period of 3 yr after RTW years²⁹⁾.

Occupational health staff should refer to this recurrent curve, to prevent relapses after RTW. This study may help prevent relapses due to depression, by showing that the occupational health professionals should follow up RTW employees for about 3 yr.

Clinical treatment alone may be insufficient to reduce the individual and economic impact of mental disorders in the workplace¹³⁾. Studies researching the prognosis of employees with depression are quite important for occupational health professionals.

There are three strengths of this study. Firstly, the number of subjects was more than 500 employees for recurrent sickness absence, higher than in previous studies, which ranged from 71 to 431 subjects^{1, 20,21,22,23,24, 26)}, except the Dutch study¹⁹⁾. Secondly, the follow-up period (2.5 to 8.5 yr) in this study was comparatively longer than in previous studies^{1, 15,16,17,18,19,20, 22)}. Thirdly, the follow-up rate was 96.9%, which was generally quite high^{1, 19,20,21,22,23,24, 26)}. The reason for the high follow-up rate may be that all the information on sickness absence is registered in the data system according to company regulations.

Many companies in Japan have been introducing RTW systems recently according to psychiatric experts’ opinions or guidelines from the Ministry of Health, Labor and Welfare in 2004, but there have been few epidemiological studies of recurrent sickness absence due to depression after RTW. The study gives rise to knowledge which may be helpful in preventing relapses.

There are several limitations of this study to note. First, as a diagnosis of depression, we used certificates submitted by different psychiatrists in daily clinical practice. It is therefore necessary to check the validity of their diagnosis, although it may be safe to assume that they use the ICD-10 diagnosis of a single depressive episode in their daily clinical practice with sufficient precision³⁰⁾. Second, we could not reject the existence of comorbidities of depression. Occupational physicians register one diagnosis per one absence episode, but employees among this population may have other psychiatric disorders³¹⁾. Third, we need to pay attention when generalizing the results of this study to other IT companies and other fields of work, whether this study is representative for the companies in other fields of work, as the subjects were all full-time workers employed by a large Japanese IT company. In addition, we did not know the number of employees who had episodes of sickness absence due to depression but left the company without showing willingness to RTW. Fourth, we cannot completely rule out all the employees who had previous episodes of psychiatric disorder before the follow-up period, because there can be some employees who had had previous episodes of psychiatric disorder before working in this company and had no episode after employed. Fifth, as we don’t have such data that can become a comparison group, such as individuals without depression, it is impossible to gain knowledge on whether recurrent sickness absence is more or less common among individuals with depression compared to individuals with other health problems.

While the RTW process itself is rarely studied³²⁾, as future tasks, predictors of recurrent sickness absence should be investigated in order to draft a strategy for preventing relapses after RTW. The three following predictors may be included: disorder-related factors (diagnosis, level of depressive symptoms, duration of the disorder), personal factors (gender, age, marital status, recovery expectations, educational level), and environmental factors (job demand, supervisory support, and co-worker support)³³⁾.

During the 8.5 year follow-up period, almost half of the RTW employees experienced recurrent sickness absence. There was a steep increase in recurrent rates the first two years after RTW, and 85.2% of total recurrence of sickness absence had occurred within three years after the index episode. This study may help prevent relapses due to depression, by showing that the occupational health professionals should follow up RTW employees for about 3 years.

This study was supported by all the staff of Metropolitan Health Administration Center, NTT East and the Department of Public Health, Dokkyo Medical University.

• 1)  van Weel-Baumgarten E, van den Bosch W, van den Hoogen H, Zitman FG (1998) Ten year follow-up of depression after diagnosis in general practice. Br J Gen Pract 48, 1643–6.
• 2)  Muto T, Sumiyoshi Y, Sawada S, Momotani H, Itoh I, Fukuda H, Taira M, Kawagoe S, Watanabe G, Minowa H, Takeda S (1999) Sickness absence due to mental disorder in Japanese workforce. Ind Health 37, 243–52.
• 3)  Kessler RC, Chiu WT, Demler O, Merikangas KR, Walters EE (2005) Prevalence, severity, and comorbidity of 12-month DSM-IV disorders in the National Comorbidity Survey Replication. Arch Gen Psychiatry 62, 617–27.
• 4)  Bijl RV, Ravelli A, van Zessen G (1998) Prevalence of psychiatric disorder in the general population: results of The Netherlands Mental Health Survey and Incidence Study (NEMESIS). Soc Psychiatry Psychiatr Epidemiol 33, 587–95.
• 5)  Kawakami N (2007) Epidemiology of depressive disorders in Japan and the world. Nippon Rinsho 65, 1578–84 (in Japanese).
• 6)  Hensing G, Wahlström R (2004) Chapter 7. Sickness absence and psychiatric disorders. Scand J Public Health Suppl 63, 152–80.
• 7)  Hirokawa S, Kawakami N, Matsumoto T, Inagaki A, Eguchi N, Tsuchiya M, Katsumata Y, Akazawa M, Kameyama A, Tachimori H, Takeshima T (2012) Mental disorders and suicide in Japan: a nation-wide psychological autopsy case-control study. J Affect Disord 140, 168–75.
• 8)  “Jisatsu no gaiyou shiryou in 2008” National Police Angency, Japan. http://www8.cao.go.jp/jisatsutaisaku/whitepaper/w-2008/pdf/gaiyou/index.html. (in Japanese)
• 9)  Foss L, Gravseth HM, Kristensen P, Claussen B, Mehlum IS, Skyberg K (2010) Risk factors for long-term absence due to psychiatric sickness: a register-based 5-year follow-up from the Oslo Health Study. J Occup Environ Med 52, 698–705.
• 10)  Okumura Y, Higuchi T. (2011) Cost of depression among adults in Japan. Prim Care Companion CNS Disord 13, PCC.10m01082.
• 11)  Knudsen AK, Harvey SB, Mykletun A, Overland S (2012) Common mental disorders and long-term sickness absence in a general working population. The Hordaland Health Study. Acta Psychiatr Scand 2012, 1–11.
• 12)  Roelen CA, Koopmans PC, Hoedeman R, Bültmann U, Groothoff JW, van der Klink JJ (2009) Trends in the incidence of sickness absence due to common mental disorders between 2001 and 2007 in the Netherlands. Eur J Public Health 19, 625–30.
• 13)  Sanderson K, Andrews G (2006) Common mental disorders in the workforce. recent findings from descriptive and social epidemiology. Can J Psychiatry 51, 63–75.
• 14)  Hensing G, Andersson L, Brage S (2006) Increase in sickness absence with psychiatric diagnosis in Norway: a general population-based epidemiologic study of age, gender and regional distribution. BMC Med 4, 19.
• 15)  Ministry of Health, Labour and Welfare of Japan (2009) Reinstatement Support Guidelines for the Workers Who Were Absent Due to Mental Health Problems. Rev ed. Mar. http://www.mhlw.go.jp/new-info/kobetu/roudou/gyousei/anzen/dl/101004–1.pdf. (in Japanese)
• 16)  Roelen CA, Koopmans PC, Anema JR, van der Beek AJ (2010) Recurrence of medically certificated sickness absence according to diagnosis: a sickness absence register study. J Occup Rehabil 20, 113–21.
• 17)  Kanai T, Takeuchi H, Furukawa TA, Yoshimura R, Imaizumi T, Kitamura T, Takahashi K (2003) Time to recurrence after recovery from major depressive episodes and its predictors. Psychol Med 33, 839–45.
• 18)  Koopmans PC, Roelen CA, Bültmann U, Hoedeman R, van der Klink JJ, Groothoff JW (2010) Gender and age differences in the recurrence of sickness absence due to common mental disorders: a longitudinal study. BMC Public Health 10, 426.
• 19)  Koopmans PC, Roelen CA, Groothoff JW (2008) Risk of future sickness absence in frequent and long-term absentees. Occup Med (Lond) 58, 268–74.
• 20)  Simpson HB, Nee JC, Endicott J (1997) First-episode major depression. Few sex differences in course. Arch Gen Psychiatry 54, 633–9.
• 21)  Mueller TI, Leon AC, Keller MB, Solomon DA, Endicott J, Coryell W (1999) Recurrence after recovery from major depressive disorder during 15 years of observational follow-up. Am J Psychiatry 156, 1000–6.
• 22)  Maj M, Veltro F, Pirozzi R, Lobrace S, Magliano L (1992) Pattern of recurrence of illness after recovery from an episode of major depression: a prospective study. Am J Psychiatry 149, 795–800.
• 23)  Pintor L, Torres X, Navarro V, Matrai S, Gastó C (2004) Is the type of remission after a major depressive episode an important risk factor to relapses in a 4-year follow up? J Affect Disord 82, 291–6.
• 24)  Eaton WW, Anthony JC, Gallo J, Cai G, Tien A, Romanoski A, Lyketsos C, Chen LS (1997) Natural history of Diagnostic Interview Schedule/DSM-IV major depression. The Baltimore Epidemiologic Catchment Area follow-up. Arch Gen Psychiatry 54, 993–9.
• 25)  Solomon DA, Keller MB, Leon AC, Mueller TI, Lavori PW, Shea MT, Coryell W, Warshaw M, Turvey C, Maser JD, Endicott J (2000) Multiple recurrences of major depressive disorder. Am J Psychiatry 157, 229–33.
• 26)  Eaton WW, Shao H, Nestadt G, Lee HB, Bienvenu OJ, Zandi P (2008) Population-based study of first onset and chronicity in major depressive disorder. Arch Gen Psychiatry 65, 513–20.
• 27)  Arends I, van der Klink JJ, Bültmann U (2010). Prevention of recurrent sickness absence among employees with common mental disorders: design of a cluster-randomised controlled trial with cost-benefit and effectiveness evaluation. BMC Public Health 10, 132.
• 28)  Hardeveld F, Spijker J, De Graaf R, Nolen WA, Beekman AT (2010) Prevalence and predictors of recurrence of major depressive disorder in the adult population. Acta Psychiatr Scand 122, 184–91.
• 29)  Koopmans PC, Bültmann U, Roelen CA, Hoedeman R, van der Klink JJ, Groothoff JW (2011) Recurrence of sickness absence due to common mental disorders. Int Arch Occup Environ Health 84, 193–201.
• 30)  Bock C, Bukh JD, Vinberg M, Gether U, Kessing LV (2009) Validity of the diagnosis of a single depressive episode in a case register. Clin Pract Epidemiol Ment Health 5, 4.
• 31)  Kessler RC, Berglund P, Demler O, Jin R, Koretz D, Merikangas KR, Rush AJ, Walters EE, Wang PS, National Comorbidity Survey Replication (2003) The epidemiology of major depressive disorder: Results from the National Comorbidity Survey Replication (NCS-R). JAMA 289, 3095–105.
• 32)  De Rijk A, Nijhuis F, Alexanderson K (2009) Gender differences in work modifications and changed job characteristics during the RTW process: a prospective cohort study. J Occup Rehabil 19, 185–93.
• 33)  Nieuwenhuijsen K, Verbeek JH, de Boer AG, Blonk RW, van Dijk FJ (2006) Predicting the duration of sickness absence for patients with common mental disorders in occupational health care. Scand J Work Environ Health 32, 67–74.