Abstract

Background The mental health of nurses is an important issue.

Aims To examine relationships between effort–reward imbalance (ERI) and depression and anxiety in nurses of a Japanese general hospital.

Methods A self-report survey was conducted among 406 nurses. Work stress was measured using a Japanese version of the ERI scale. Depression and anxiety were assessed by an item of the QOL-26. Logistic regression analysis was used to determine the independent contribution of the effort–reward ratios or overcommitment to the depressive state.

Results Both higher effort–money ratio and higher overcommitment significantly correlated with the depressive state (OR: 2.75; 95% CI: 1.34–5.66 and OR: 1.27; 95% CI: 1.15–1.41, respectively).

Conclusions These findings suggest that in addition to effort–money ratio, overcommitment at work is an especially important issue that may be able to be managed in health promotion services for nurses in general hospitals.

Introduction

Nurses are exposed to high-stress work environments. Weyers et al. [1] found that effort–reward imbalance (ERI) was significantly related to poor physical and psychological health in a sample of Danish nurses.

We conducted a self-report survey among nurses to investigate the influence of ERI on their mental health. The aim of the present study was to investigate the relationship between ERI and depressive state in nurses at a Japanese general hospital.

Methods

The study was approved by the Committee for the Prevention of Physical Disease and Mental Illness among Health Care Workers in our hospital.

Study subjects consisted of nurses at a general hospital in Japan. The questionnaire was distributed by supervisors. We surveyed their age- and work-related variables (work style, occupational status and overtime work) (Table 1). Age was coded into a four-category classification in order to prevent identifying individuals. Work was categorized as full time or part-time. Occupational status responses were for manager, middle manager or subordinates. Overtime work responses were for 50 h/week or ≥50 h/week, given that ≥50 working hours has been significantly related to ERI [2].

Table 1.

Comparison between the group with depression and anxiety and the group without them

 All nurses (n = 406) Group with depression and anxiety (n = 125) Group without depression and anxiety (n = 141) Chi-square value Response rate (%) 
 n (%) n (%) n (%)   
Age, year    6.37 (n.s.) 99 
    <30 272 (67) 87 (33) 92 (35)   
    30 to <40 91 (22) 30 (11) 30 (11)   
    40 to <50 25 (6) 5 (2) 13 (5)   
    >50 13 (3) 2 (1) 5 (2)   
    Non-responders 5 (12) 1 (0) 1 (0)   
Work style    1.38 (n.s.) 96 
    Full time 368 (91) 113 (44) 130 (51)   
    Part-time 21 (5) 5 (2) 7 (3)   
    Non-responders 17 (4) 7 (3) 4 (2)   
Occupational status    2.49 (n.s.) 100 
    Manager 18 (4) 2 (1) 7 (3)   
    Middle manager 21 (5) 8 (3) 7 (3)   
    Subordinate 367 (90) 115 (43) 127 (48)   
    Non-responders 0 (0) 0 (0) 0 (0)   
Overtime work, h/week    1.33 (n.s.) 87 
    <50 353 (87) 112 (47) 125 (53)   
    ≥50 1 (0) 1 (0) 0 (0)   
    Non-responders 52 (13) 12 (6) 16 (6)   
 Mean (SD) Mean (SD) Mean (SD) t value  
Effort–reward ratio 0.86 (0.42) 10.9 (0.51) 0.72 (0.31) 7.09***  
Effort–esteem ratio 0.83 (0.44) 1.04 (0.56) 0.69 (0.31) 6.29***  
Effort–job security ratio 0.86 (0.55) 1.13 (0.79) 0.70 (0.34) 5.86***  
Effort–money ratio 0.97 (0.55) 1.26 (0.73) 0.81 (0.39) 6.38***  
Overcommitment 15.8 (3.54) 17.87 (3.41) 14.35 (3.25) 8.62***  
 All nurses (n = 406) Group with depression and anxiety (n = 125) Group without depression and anxiety (n = 141) Chi-square value Response rate (%) 
 n (%) n (%) n (%)   
Age, year    6.37 (n.s.) 99 
    <30 272 (67) 87 (33) 92 (35)   
    30 to <40 91 (22) 30 (11) 30 (11)   
    40 to <50 25 (6) 5 (2) 13 (5)   
    >50 13 (3) 2 (1) 5 (2)   
    Non-responders 5 (12) 1 (0) 1 (0)   
Work style    1.38 (n.s.) 96 
    Full time 368 (91) 113 (44) 130 (51)   
    Part-time 21 (5) 5 (2) 7 (3)   
    Non-responders 17 (4) 7 (3) 4 (2)   
Occupational status    2.49 (n.s.) 100 
    Manager 18 (4) 2 (1) 7 (3)   
    Middle manager 21 (5) 8 (3) 7 (3)   
    Subordinate 367 (90) 115 (43) 127 (48)   
    Non-responders 0 (0) 0 (0) 0 (0)   
Overtime work, h/week    1.33 (n.s.) 87 
    <50 353 (87) 112 (47) 125 (53)   
    ≥50 1 (0) 1 (0) 0 (0)   
    Non-responders 52 (13) 12 (6) 16 (6)   
 Mean (SD) Mean (SD) Mean (SD) t value  
Effort–reward ratio 0.86 (0.42) 10.9 (0.51) 0.72 (0.31) 7.09***  
Effort–esteem ratio 0.83 (0.44) 1.04 (0.56) 0.69 (0.31) 6.29***  
Effort–job security ratio 0.86 (0.55) 1.13 (0.79) 0.70 (0.34) 5.86***  
Effort–money ratio 0.97 (0.55) 1.26 (0.73) 0.81 (0.39) 6.38***  
Overcommitment 15.8 (3.54) 17.87 (3.41) 14.35 (3.25) 8.62***  

n.s., not significant.

***P < 0.001.

Work stress was measured using the Japanese version of the ERI (23 items) translated by Tsutsumi et al. [3]. The ERI consists of three subscales: efforts, rewards and overcommitment. The reward subscale is further divided into three subgroups: esteem, job security and money. The validity of this questionnaire has been confirmed [2,3]. The ERI model indicates that work stress is related to high effort with low reward. Higher ERI ratio and overcommitment scores indicate high-risk conditions for physical or mental disorders.

Depression and anxiety were measured using one item of the QOL-26. According to a report of the World Health Organization/Quality of Life group [4], item 26 questioned how often the subject feels negative feelings such as depressed mood, disappointment, sadness, grief, despair, lack of pleasure, anxiety, guilt or nervousness. Moreover, assessment of item 26 takes into consideration clinical level of disorders such as depressive disorders, mood disorders and anxiety disorders including phobia. According to Suzanne et al. [5], decrease of negative feelings score (item 26) significantly correlated with reduction in depression symptoms assessed by the Beck Depression Inventory. Assessment of item 26 does not lead to diagnosis of depression but conceptually suggests severity of depressive state. This item was estimated on a five-point scale, which ranged from ‘Never (1)’ to ‘Very severe (5)’.

Four kinds of ERI ratios (effort–reward, effort–esteem, effort–job security and effort–money) were calculated according to Tsutsumi et al. [3]. The item 26 score was coded by using dummy categorical variables for logistic analyses. Subjects who answered the item question with Never (1) or Seldom (2) were assigned to the group without depression and anxiety (n = 141). Subjects who answered the item question with Severe (4) or Very severe (5) were assigned to the group with depression and anxiety (n = 125). They were not necessarily patients with depressive disorder and anxiety disorder. Subjects who answered the item question with Moderate (3) (n = 140) were excluded from the analyses.

Age- and work-related variables were compared between the two groups using the chi-square test. In addition, we compared the means of the four ERI ratios and overcommitment between the two groups using the t-test. In the next step, multiple logistic regression analysis was conducted to examine the relationship between depression and anxiety and the variables that had shown significant differences between the two groups by the chi-square test or t-test. We used the depression and anxiety scores as dependent variables and the other scores as independent variables. Then, using stepwise logistic regression, the relationship between the depressive state and the other variables was estimated. The results were shown as odds ratios with 95% confidence intervals. All analyses were conducted using SPSS 11 (SPSS Inc., Chicago, IL, USA).

Results

The questionnaire was returned by 465 of 682 nurses giving a response rate of 68%. Male nurses were excluded from the sample due to their small numbers (n = 13). Subjects with missing ERI values were also excluded (n = 46). The final sample consisted of 406 nurses (60%). We found significant differences for all the ERI ratios and overcommitment between the two groups (Table 1). On the other hand, we found no significant differences for age- or work-related variables between the two groups (Table 1). Regarding those work-related factors, there were no significant differences between non-responders and responders (Table 1). These non-significant factors were excluded in the subsequent stepwise logistic regression analyses. The following significant correlations were independently related to depression and anxiety among nurses: a higher effort–money ratio and higher overcommitment (Table 2).

Table 2.

Odds ratios of depression and anxiety by ERB and overcommitment

 OR (95% CI) 
Effort–money imbalance 1.01 2.75 (1.34–5.66)** 
Overcommitment 0.24 1.27 (1.15–1.41)*** 
R2  0.33 
 OR (95% CI) 
Effort–money imbalance 1.01 2.75 (1.34–5.66)** 
Overcommitment 0.24 1.27 (1.15–1.41)*** 
R2  0.33 

**P < 0.01; ***P < 0.001.

Discussion

Our study identified work stress regarding ERI that were significantly associated with the depressive state in nurses at a general hospital.

The strength of our study is that we investigated in detail the independent associations of the subgroup ratios of ERI (effort–esteem, effort–job security and effort–money) and overcommitment. Depression and anxiety were significantly associated with a higher effort–money ratio and higher scores for overcommitment (Table 2). According to previous studies [2,6], ERI and overcommitment predicted mental health. We found no significant differences for age- and work-related factors between the two groups. Therefore, in accordance with previous studies, reducing nurses’ overcommitment and improving their work situation (e.g. better promotion prospects or higher salary) may predict a reduction of their depression and anxiety.

Overcommitment is a set of attitudes, behaviours and emotions that reflect excessive work effort and is combined with a strong desire for approval. Therefore, the overcommitment of nurses may be reduced through mental health services such as group cognitive psychotherapy. Further research could determine whether such mental health services actually improve mental health among nurses.

Nevertheless, the study has some weaknesses. First, we could not fully substantiate causation of depression and anxiety arising from work stress. Moreover, the sample size was small in only one general hospital. A longitudinal study of a larger sample is necessary. Second, we could not use a specified scale for depression and investigate the factors external to work such as social, family, financial factors and so on, because our survey was conducted as a primary examination for nurses’ mental health.

In conclusion, our findings provide insight into the factors associated with depressive state among nurses in a general hospital.

Key points

  • Effort–reward imbalance of the group with depression and anxiety were significantly higher than those of the group without depression and anxiety among nurses of a Japanese general hospital.

  • Depression and anxiety were significantly associated with a higher effort–money ratio and higher scores for overcommitment.

  • Reducing nurses’ overcommitment and improving their work situation (e.g. better promotion prospects or higher salary) may predict a reduction of their depression and anxiety.

Conflicts of interest

None declared.

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