Odontology (2011) 99:179–187 DOI 10.1007/s10266-011-0005-6
ORIGINAL ARTICLE
Condition of depressive symptoms among Japanese dental students Yasuko Takayama • Eiji Miura • Kazue Miura Shigeru Ono • Chikahiro Ohkubo
•
Received: 29 March 2010 / Accepted: 10 August 2010 / Published online: 7 May 2011 Ó The Society of The Nippon Dental University 2011
Abstract The Zung Self-Rating Depression Scale (SDS) is generally used to screen for the presence of depression. The purpose of this study was to investigate scores on the SDS, Japanese version, in undergraduates at Tsurumi University School of Dental Medicine in Yokohama, Japan. A total of 2,197 dental students completed the SDS from 2006 through 2008. The investigation took place each year over a 3-week period from June to July. When investigating, the Institutional Review Board at Tsurumi University approved the study. Students could voluntarily agree or decline to participate in the study, and all responses were provided anonymously. SDS scores by sex, class year, and change over time were analyzed. The mean SDS score ranged from 43.7 ± 8.5 to 44.8 ± 9.0 between 2006 and 2008. Women were significantly more depressed than men in 2007 and 2008. The SDS scores of the same students were high continuously for 2 years. ‘‘Diurnal variation,’’ ‘‘personal devaluation,’’ and ‘‘confusion’’ had the highest scores of the 20 individual items of the SDS. Of the participating students, 31.4–37.2% were classified as being moderately to severely depressed. Logistic regression analysis was used to compute the odds ratio for SDS Y. Takayama (&) E. Miura C. Ohkubo Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama 230-8501, Japan e-mail:
[email protected] K. Miura Department of Dental Anesthesiology, Tsurumi University School of Dental Medicine, Yokohama, Japan S. Ono Department of General Dentistry and Clinical Education, Tsurumi University School of Dental Medicine, Yokohama, Japan
scores of B47 versus C48. The item ‘‘suicidal rumination’’ had the highest chance of being associated with depressive symptoms in all 3 years. Although this research was limited to a single department of dentistry, it appears that dental students experience various levels of depression. Providing mental healthcare options to these students may be helpful. Keywords Depression Dental students Stress Depression scale Zung Self-Rating Depression Scale (SDS)
Introduction Two commonly used inventory-type measurements of depression include the Zung Self-Rating Depression Scale (SDS) [1] and the Center for Epidemiologic Studies Depression Scale (CES-D) [2]. The SDS, which is generally used to screen for the presence of depression, consists of 20 items based on the clinical diagnostic criteria most commonly used to characterize depressive disorders. Ten sentences are worded positively in relation to symptoms, and 10 are worded negatively; patients rate the frequency of the occurrence of each statement on a scale of 1–4. Scores range from 20 to 80 and are converted into index scores that express the actual score as a fraction of the maximum possible score. Research related to the mental health and psychological distress experienced by medical students has been conducted worldwide [3–6]. Medical students are frequently targeted in such research because of the amount of pressure they face during their schooling. Dental students also represent a highly educated population experiencing extraordinary pressures, including a heavy schedule and the
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need to learn a large amount of information in a relatively short time. For Japanese dental students, the computerbased testing and objective structured clinical examination takes place during the fourth year of schooling, clinical training starts in the fifth year, and a professional exam, graded as pass or fail, is required for graduation. Therefore, it is hypothesized that dental students experience more stress than other young people in the same age group. A counseling service is provided at our university to help maintain the mental health of students and faculty and staff members of the Department of Dentistry and other departments. This service is provided either in an office or via the telephone or Web, and counselors have received training regarding stress management and mental health issues. Some students have been known to take a leave of absence or withdraw from school, and one of the causes is thought to be mental health issues. Although many students have taken advantage of the counseling offered, the mental health of dental students is not well understood as studies focusing on mental health concerns are not as common in Japan as in Western countries. The SDS can screen for the presence of depression easily, and is multiused worldwide. It seems that levels of depression can be compared as the dental student, the medical students, and the same age groups using the SDS. The purpose of the present study was to examine scores on
the Zung SDS (Japanese version) in undergraduates at Tsurumi University School of Dental Medicine to determine the incidence of depression.
Materials and methods Investigation period and subjects Subjects were students at Tsurumi University School of Dental Medicine in Tsurumi-ku, Yokohama, Japan. The Japanese version of the Zung SDS (Table 1) [7] was administered from 2006 through 2008 to students in class years 1 through 6. The investigation took place each year over a 3-week period from June to July. The SDS was administered during lecture periods. The participating dental students filled out the SDS each year. The first-year students in the Department of Dental Hygiene of Tsurumi University, all of whom were female, were also assessed in 2006. The SDS scores were compared in terms of differences between department and sex. Students could voluntarily agree or decline to participate in the study, and all responses were provided anonymously. The only demographic information gathered was age and sex. SDS questionnaires that were not completed were excluded from the analysis. In addition, questionnaires that
Table 1 Zung Self-Rating Depression Scale Please check a response for each of the 20 items
None or a little Some of Good part of Most or all of of the time the time the time the time
1
Depressed affect
I feel downhearted, blue, and sad
1
2
3
4
2
Diurnal variation
Morning is when I feel best
4
3
2
1
3
Crying spells
I have crying spells or feel like it
1
2
3
4
4
Sleep disturbance
I have trouble sleeping through the night
1
2
3
4
5
Decreased appetite
I eat as much as I used to
4
3
2
1
6
Decreased libido
I enjoy looking at, talking to and being with attractive won
4
3
2
1
7
Weight loss
I notice that I am losing weight
1
2
3
4
8
Constipation
I have trouble with constipation
1
2
3
4
9
Tachycardia
My heart beats faster than usual
1
2
3
4
10 Fatigue
I get tired for no reason
11 Confusion My mind is as clear as it used to be 12 Psychomotor retardation I find it easy to do the things I used to do
1
2
3
4
4 4
3 3
2 2
1 1
13 Psychomotor agitation
I am restless and can’t keep still
1
2
3
4
14 Hopelessness
I feel hopeful about the future
4
3
2
1
15 Irritability
I am more irritable than usual
1
2
3
4
16 Indecisiveness
I find it easy to make decisions
4
3
2
1
17 Personal devaluation
I feel that I am useful and needed
4
3
2
1
18 Emptiness
My life is pretty full
4
3
2
1
19 Suicidal rumination
I feel that others would be better off if I were dead 1
2
3
4
20 Dissatisfaction
I still enjoy the things I used to do
3
2
1
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4
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did not include information on age and sex were excluded from the analysis of age and sex. The response rates for each year of the investigation are shown in Table 2. The Institutional Review Board at Tsurumi University approved the study. Methods of analysis and statistical analysis The Shapiro–Wilk test was used for test of normality and Levene test was used for test of homogeneity. Means and standard deviations were determined, and the SDS scores were analyzed for sex, calendar year using the Student t test (a = 0.05). The SDS scores of the total of dental students showed normal distribution in each year. However, there were groups that showed normal distribution and groups that were not normal distribution in the SDS scores of each class year. Therefore, mean of SDS scores of each class year was analyzed by Kruskal–Wallis test, Mann–Whitney test and Bonferroni’s inequality (a = 0.003). The analysis by class year was based on the year the investigation was begun. First-year students in 2006 were classified as Group A, and each subsequent class was classified from Group B to Group F. The SDS scores of each group were analyzed. However, the number of students in each group may have changed a little from year to year due to students’ withdrawing from the university or needing to repeat a year in school. Students could voluntarily agree or decline to participate in the study, and all responses were provided anonymously. Therefore, the transition of the number of students was uncertain. It was analyzed by judging the observation by the same subjects, and using Friedman test (Group A–D) and Wilcoxon signed rank test (Group E, F).
Table 2 Number of dental students and response rates Year
Number of students
Number of answers
Response rate (%)
Total
823
713
86.6
Male
504
366
72.6
Female
319
271
85.0
Total
842
741
88.0
Male
516
413
80.0
Female
326
299
91.7
Total
830
743
89.5
Male Female
509 321
404 277
79.4 86.3
2006
2007
2008
The student to whom sex turned out was targeted
SDS scores were divided into four levels of depression according to the classification proposed by Barrett et al. [8]: no or insignificant depression, 20–39 points (Level 0); mild depressive state, 40–47 points (Level 1); moderate depressive state, 48–55 points (Level 2); and severe depressive state, C56 points (Level 3). The SDS scores for each year were classified into the four levels of depression, and each ratio was compared (Kruskal–Wallis test) (a = 0.05). The 20 items of the SDS were examined in terms of their relation to the SDS score, the tendency to experience each level of a depressive state, and the factors related to experiencing a depressive state. For each item, a correlation coefficient for the SDS score was determined, and logistic regression analysis was performed. Logistic regression analysis was used to compute the odds ratio and 95% confidence intervals. The SDS score was assumed to be the dependent variable (0, score B47 and 1, score C48), and the independent variable was the response for each of the 20 items (0, none or a little of the time and some of the time; 1, good part of the time and most or all of the time). All statistical analysis were in software (SPSS for Windows Ver.12.0, SPSS Japan Inc., Tokyo, Japan).
Results SDS scores A total of 2,197 dental students completed the SDS from 2006 through 2008. The mean ages of the dental students were 22.1 years (range, 19.2–25.2 years) in 2006, 22.1 years (range, 19.6–24.8 years) in 2007, and 22.1 years (range, 19.2–24.8 years) in 2008. The number of subjects and mean SDS scores for each year are shown in Table 3. Mean SDS scores ranged from 43.7 ± 8.5 to 44.8 ± 9.0 over the 3 years and did not differ significantly by year. Mean scores for male students were significantly lower than those for female students in 2007 (p \ 0.05) and 2008 (p \ 0.01). Mean SDS scores for each class year are presented in Table 4. In 2006, SDS scores were high for the fourth-year students. In 2007 and 2008, scores were high for the fifthyear students, and were high for the second-year students in 2008. However, these were the same students who showed high SDS scores in 2006 and 2007. Mean SDS scores for each class year had a significant difference both for 3 years as a result of Kruskal–Wallis test (p \ 0.01). Changes in the SDS scores of each group of students are shown by class year in Table 5. The scores of the students in Groups A, B and C did not change significantly over the 3 years. In contrast, the scores of subjects who were fifthyear students in 2006 significantly increased as they
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Table 3 Mean of SDS scores Year 2006 Total Male Female 2007 Total Male Female 2008 Total Male Female
p
Mean SD
N
713 43.7 366 43.5 271 43.8
8.5 8.7 8.3
741 44.8 413 44.2 299 45.6
9.0 9.2 8.6
743 44.0 404 42.9 277 44.9
9.0 9.1 8.6
Table 5 Mean of SDS scores of each group Class year Group A Group B Group C Group D Group E Group F
43.6
44.2
3
43.7
43.0
42.7
41.6
43.0
45.6
45.4
45.4
47.9
42.5
6
44.6
44.9
p
p \ 0.05 p \ 0.05
p < 0.01
Four levels of depression The distribution of scores on the Zung SDS over 3 years is shown in Table 6. From 62.8 to 68.6% of dental students showed no or mild depression (Level 0 and Level 1), whereas 7.4–12.4% showed severe depression (Level 3) between 2006 and 2008. Significantly more females than males showed moderate or severe depression (Level 2 or 3) in 2007 and 2008. No depression (Level 0), mild depression (Level 1), moderate depression (Level 2), and severe depression (Level 3) were seen in 17.9, 31.4, 36.4, and 14.3%, respectively, of dental hygiene students (data not shown).
Group N
Min
Max Mean SD
A B C D E
117 106 126 129 131 104 713
28 28 24 26 24 23 23
80 62 70 75 66 72 80
45.2 43.6 42.7 45.6 42.5 42.5 43.7
F A B C D E
128 127 125 111 125 125 741
23 27 26 28 29 25 23
69 74 68 62 80 69 80
44.2 9.0 45.3 8.3 43.0 8.4 43.0 8.4 47.9 10.0 44.9 8.7 44.8 9.0
120 138 121 124 115 125 743
23 23 25 20 26 24 20
71 71 80 67 73 63 80
42.9 45.4 43.7 41.6 45.4 44.6 44.0
p
8.2 8.1 7.9 9.5 7.9 8.6 8.5
8.3 9.5 9.0 8.4 9.8 8.1 9.0
SDS items * *
*
* *
*p \ 0.05
entered the sixth year (Group E). Moreover, scores of subjects who were fourth-year students in 2006 increased in 2007 and then decreased in 2008 (Group D). As students progressed through the dental program, the tendency of their SDS scores to increase and decrease differed by subjects. The mean SDS scores of the first-year dental hygiene students (n = 140, mean SDS score = 47.0 ± 7.5) were higher than those of the first-year dental students (n = 713, mean SDS score = 43.7 ± 8.5) and the first-year female dental students (n = 55, mean SDS score = 45.7 ± 8.0), although the differences did not reach statistical significance.
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45.4
5
Table 4 Mean of SDS scores of each school year
F A B C D
45.2
2 4 p < 0.05
The student to whom sex turned out was targeted
School year Year 2006 1 2 3 4 5 6 Total Year 2007 1 2 3 4 5 6 Total Year 2008 1 2 3 4 5 6 Total
1
The results of mean scores for the 20 individual items of the SDS are shown in Table 7. ‘‘Diurnal variation,’’ ‘‘personal devaluation,’’ and ‘‘confusion’’ had the highest SDS scores. ‘‘Tachycardia’’ and ‘‘suicidal rumination’’ had the lowest SDS scores. It was only for ‘‘diurnal variation’’ that the mean score was C3.0 regardless of the level of depression. The means scores each year for ‘‘diurnal variation,’’ ‘‘fatigue,’’ ‘‘confusion,’’ ‘‘psychomotor retardation,’’ ‘‘hopelessness,’’ ‘‘indecisiveness,’’ ‘‘personal devaluation,’’ ‘‘emptiness,’’ and ‘‘dissatisfaction’’ were C3.0 in moderate depression and severe depression (data not shown). Correlations between SDS scores and the individual items in each year are shown in Table 8. There was a significant correlation between the SDS score and each 20 items in each year (p \ 0.01). Table 8 shows Pearson’s product moment correlation coefficient. ‘‘Depressed affect,’’ ‘‘emptiness,’’ and ‘‘dissatisfaction’’ were highly correlated with the total SDS score every year. The factors that influenced the state of depression are presented in Table 9. Logistic regression analysis was used to compute the odds ratio for SDS score B47 versus C48. ‘‘Suicidal rumination’’ had the highest chance of being associated with depressive symptoms in 2006, ‘‘tachycardia’’ and ‘‘suicidal rumination’’ in 2007, and ‘‘depressed affect’’ and ‘‘suicidal rumination’’ in 2008.
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Table 6 Distribution of scores on the SDS
Table 7 Mean scores on each SDS item for students in the Department of Dentistry
Zung Self-Rating Depression Scale score Level 0 (20–39) Level 1 (40–47) % % N N 2006 Total 236 33.1 253 35.5 2007 Total 214 28.9 251 33.9 2008 Total 254 34.2 251 33.8 2006 Male 121 33.0 138 37.7 Female 93 34.3 88 32.5 2007 Male 127 30.8 148 35.8 Female 78 26.1 93 31.1 2008 Male 160 39.6 132 32.7 Female 81 29.2 99 35.7
Level 2 (48–55) Level 3 ( 56) p % % N N 171
24.0
53
7.4
184
24.8
92
12.4
161
21.7
77
10.4
79 67
21.6 24.7
28 23
7.7 8.5
87 91
21.1 30.4
51 37
12.3 12.4
p
0.05
77 66
19.1 23.8
35 31
8.7 11.2
p
0.05
Year
2006
Item no.
Mean item score
SD
Mean item score
SD
Mean item score
SD
1
1.92
0.82
1.94
0.84
1.89
0.84
2
3.37
0.81
3.35
0.80
3.31
0.80
3
1.61
0.78
1.67
0.81
1.60
0.76
4
1.67
0.85
1.80
0.92
1.72
0.89
5
1.89
1.04
1.86
0.97
1.94
1.02
6
2.38
1.08
2.39
1.04
2.42
1.04
7
1.50
0.86
1.51
0.82
1.52
0.81
8
1.59
0.89
1.59
0.90
1.55
0.82
9
1.39
0.68
1.46
0.73
1.39
0.70
10
2.80
0.99
2.83
0.97
2.64
0.96
11 12
2.81 2.40
0.90 0.95
2.90 2.40
0.87 0.88
2.87 2.44
0.86 0.91
13
1.85
0.90
1.86
0.93
1.79
0.88
14
2.33
1.04
2.45
1.03
2.52
1.00
15
2.00
0.85
2.16
0.91
2.04
0.91
16
2.74
0.97
2.77
0.93
2.75
0.94
17
2.84
0.91
2.87
0.94
2.89
0.90
18
2.54
0.97
2.68
0.94
2.56
0.95
19
1.36
0.71
1.47
0.80
1.41
0.76
20
2.70
0.99
2.81
0.94
2.71
0.96
Discussion Studies of relatively young subjects have shown that these subjects tend to have high SDS scores and that scores become lower with advancing age (2,258 Japanese undergraduates [9] and 3,178 workers at a railway company [10]). Zung [11] reported that mean SDS scores in subjects aged 19 or younger were 31.2. Knight et al. [12] showed that subjects aged 16–19 years had SDS scores of 33.0 for
2007
2008
boys and 37.2 for girls. Hymes and Akiyama [13] reported that the mean SDS score for Japanese students (n = 116 undergraduates at two universities) was 41.80 ± 8.31. Chida et al. [14] showed that the mean SDS scores of randomly selected subjects were 39.1 ± 7.6 for males (n = 579) and 41.2 ± 8.2 for females (n = 665) among those aged 20–39 years. Liu et al. [15] investigated 2,462 students aged 13–22 years in China and reported mean SDS scores of 44.8 (SD 9.9). The mean SDS scores of
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Table 8 Correlation between SDS scores and 20 SDS items in each year Item of SDS
2006
2007
2008
1
Depressed affect
0.633
0.691
0.703
2
Diurnal variation
0.259
0.303
0.359
3
Crying spells
0.491
0.573
0.540
4
Sleep disturbance
0.463
0.435
0.415
5
Decreased appetite
0.394
0.460
0.410
6
Decreased libido
0.265
0.244
0.234
7 8
Weight loss Constipation
0.190 0.261
0.218 0.269
0.215 0.358
9
Tachycardia
0.503
0.525
0.518
10
Fatigue
0.550
0.613
0.600
11
Confusion
0.624
0.623
0.638
12
Psychomotor retardation
0.578
0.598
0.603
13
Psychomotor agitation
0.331
0.445
0.433
14
Hopelessness
0.602
0.570
0.622
15
Irritability
0.531
0.630
0.578
16
Indecisiveness
0.397
0.360
0.414
17
Personal devaluation
0.492
0.513
0.547
18
Emptiness
0.682
0.682
0.701
19
Suicidal rumination
0.495
0.534
0.550
20
Dissatisfaction
0.651
0.674
0.681
students in the present study ranged from 43.7 ± 8.5 to 44.8 ± 9.0 from 2006 through 2008. Mean SDS scores in our survey were higher than those previously reported, however, it approximated with the result of the survey of China. [15] The female students’ scores were higher than those of male students in 2007 and 2008. Our results were comparable to those of other studies in that we showed higher SDS scores for females than for males [16–18]. Moreover, the difference was hardly seen for the investigation period of 3 years as for the mean SDS score. Inam et al. [3] reported that the prevalences of anxiety and depression among fourth-year, third-year, second-year, and first-year medical students were 49, 47, 73, and 66%, respectively. Chandavarkar et al. [4] reported that anxiety, attentional, and depressive symptoms were highest in thirdyear medical students. In contrast, obsessional symptoms were highest in the first-year students and lower for subsequent years [4]. In the present study, mean SDS scores of fifth-year dental students in 2007 and 2008 were highest. This investigation took place each year over a 3-week period from June to July. To avoid the influence of the apathy syndrome that contracts easily a disease in April and May as much as possible, the investigation was done within that time frame. It was the time when the fifth-year students began the clinical training and the sixth-year students ended it. The investigated time seems to be mentally
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steady comparatively excluding the fifth-year and the sixthyear students. However, scores were inconsistent as students moved into the upper-level classes, with some groups showing increases and others showing decreases. A longerterm study is necessary to show the presence or absence of a consistent tendency of dental students for SDS scores over time. Barrett et al. [8] proposed four levels of depression, which we examined in this study. In his classification, Level 0 represents no or insignificant symptoms; Level 1 represents definite symptoms of depression present during the month; Level 2 represents a greater degree of depressive symptoms, corresponding to the level that might be seen in outpatients with depression as the main problem; and Level 3 represents depressive symptoms present to a marked degree, dominating the clinical picture. In patients with Level 3 depression, the disease is equivalent to that seen in psychiatric patients either hospitalized for depression or experiencing a severe depressive neurosis [8]. Liu et al. [15] reported that the prevalence rate of depression was 16.9% among 2,462 students aged 13–22 from Shandong Province, China. Chida et al. [14] showed that Levels 2 and 3 occurred in 13.1% of males and 20.6% of females aged 20–39 years from the general population in Yamagata, Japan. Yamazaki et al. [19] investigated 4,500 people aged 16 years or older who were selected by stratifiedrandom sampling from the population of Japan; 14.0% had moderate or severe depressive symptoms and 2.0% had severe depressive symptoms as measured with the SDS. In the present study, 21.7–24.8% of dental students were classified as moderately depressed, and 7.4–12.4% were classified as severely depressed between 2006 and 2008. It seems that the percentage of dental students with moderate or severe depression was higher in the present study than in other studies. Inam et al. [3] reported that 113 (60%) of 189 medical school students in Pakistan experienced anxiety and depression. Rab et al. [5] showed that 43.7% of 87 randomly selected female medical students at another medical college in Pakistan reported anxiety and 19.5% reported depression. Aniebue and Onyema [6] used the SDS to assess the epidemiology of depressive symptoms in 262 Nigerian medical students and reported that the prevalence of depression was 23.3% among students aged 16–30 years. Chan [20] examined depressive symptoms and symptom dimensions of 335 undergraduate Chinese medical students using the Beck Depression Inventory (BDI). Although male and female medical students did not differ in the degree of depressed mood as reflected in the BDI scores, half of the Chinese medical students were classified as depressed, and 2% were classified as severely depressed [20]. In the present study, 31.4–37.2% of dental students were classified as moderately and severely
p
0.000 0.001 0.000
Variable
Depressed affect
Diurnal variation
Crying spells
Sleep disturbance Decreased appetite
Decreased libido
Weight loss
Constipation
Tachycardia
Fatigue
Confusion
Psychomotor retardation
Psychomotor agitation
Hopelessness
Irritability
Indecisiveness
Personal devaluation
Emptiness
Suicidal rumination Dissatisfaction
Constant
Item
1
2
3
4 5
6
7
8
9
10
11
12
13
14
15
16
17
18
19 20
Odds ratios: SDS score B47 versus C48
0.003
0.003
0.003
0.000
0.000
0.015
0.000
0.004
0.001
0.010
0.000
0.000
0.000
0.000 0.000
0.001
0.130
0.000
2006
Year
0.000
18.221 6.166
3.703
5.526
3.367
5.243
9.008
3.153
4.410
4.683
3.293
7.469
5.587
8.852
3.484
8.528 3.822
7.446
2.511
8.320
Odds ratio
4.310 2.137
1.565
1.819
1.493
2.267
4.167
1.250
2.177
1.623
1.627
1.602
2.134
2.890
1.764
3.159 1.911
2.207
0.763
3.241
Confidence interval
77.021 17.793
8.765
16.783
7.592
12.130
19.472
7.955
8.935
13.512
6.663
34.814
14.626
27.109
6.881
23.018 7.644
25.119
8.271
21.361
Confidence limits
0.000
0.000 0.002
0.000
0.004
0.000
0.002
0.000
0.000
0.004
0.022
0.004
0.000
0.000
0.000
0.000
0.000 0.000
0.002
0.002
0.000
p
2007
Table 9 Examination of factor that influences state of depression (logistic regression analysis)
0.000
23.597 6.552
11.038
4.840
11.278
3.551
7.348
10.011
2.942
3.592
3.025
24.224
9.676
16.099
5.001
9.263 9.151
7.362
6.118
19.928
Odds ratio
5.046 1.981
3.669
1.656
4.134
1.622
3.328
3.969
1.421
1.199
1.419
4.617
3.640
4.967
2.428
3.450 4.249
2.077
1.967
6.150
Confidence interval
110.344 21.672
33.209
14.140
30.768
7.775
16.223
25.252
6.090
10.765
6.446
127.103
25.718
52.187
10.298
24.875 19.710
26.101
19.028
64.579
Confidence limits
0.000
0.001 0.000
0.000
0.113
0.000
0.003
0.000
0.026
0.000
0.006
0.000
0.601
0.000
0.051
0.001
0.000 0.000
0.013
0.535
0.000
p
2008
0.000
11.014 8.060
5.365
2.105
4.772
3.570
4.379
2.943
4.706
5.841
7.976
1.602
8.132
2.892
3.713
5.935 6.071
6.217
1.410
14.010
Odds ratio
2.819 3.070
2.169
0.839
2.111
1.550
1.952
1.137
2.100
1.664
3.646
0.273
2.692
0.995
1.663
2.380 2.829
1.475
0.476
4.606
Confidence interval
43.025 21.160
13.269
5.283
10.785
8.223
9.824
7.619
10.547
20.496
17.449
9.386
24.569
8.406
8.291
14.797 13.027
26.204
4.175
42.614
Confidence limits
Odontology (2011) 99:179–187 185
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depressed. This result was not a value that was lower than the ratio of medical students though it was not possible to say indiscriminately. ‘‘Diurnal variation’’ had the highest score in the present study. Liu et al. [15] reported that the mean value of each item on the SDS ranged from a high of 2.49 for ‘‘indecisiveness’’ to a low of 1.15 for ‘‘suicidal ideation.’’ In that study, other items with higher mean scores (C2) included ‘‘diurnal variation,’’ ‘‘decreased appetite,’’ ‘‘decreased libido,’’ ‘‘confusion,’’ ‘‘psychomotor retardation,’’ ‘‘indecisiveness,’’ and ‘‘emptiness’’ [15]. In the present study, mean values for each item on the SDS ranged from a high of 3.31–3.37 for ‘‘diurnal variation’’ to a low of 1.36–1.47 for ‘‘tachycardia’’ and ‘‘suicidal rumination,’’ and the mean score of 11 items was C2 between 2006 and 2008. Kitamura et al. [21] distributed the SDS to 28,588 first-year university students and found that ‘‘diurnal variation,’’ ‘‘decreased libido,’’ ‘‘hopelessness,’’ ‘‘indecisiveness,’’ ‘‘personal devaluation,’’ and ‘‘emptiness’’ were associated with SDS scores C2. In that study [21], ‘‘diurnal variation’’ had the highest value (2.9 ± 0.9), which is similar to our findings and may be a result of the everyday lifestyle of modern youth. In this study, ‘‘suicidal rumination’’ and ‘‘depressed affect’’ were highly associated with the level of depression. Innamorati et al. [22] suggested that SDS is a good predictor of suicide risk and discriminates individuals at lower risk from those at higher risk. Thus, attention should be focussed on students with high scores on these items. On the whole, psychological symptoms (items 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20) showed a higher association with depression than did physiological symptoms (items 2, 4, 5, 6, 7, 8, 9, and 10) in this study (see Table 9 for a list of items). One limitation of the present study was that it only examined dental students in one region of Japan. Thus, the results cannot be generalized to all dental students as it is possible that the state of depression is influenced by the region where the student lives as well as the university attended. However, the results do show that many of the dental students experienced depression and indicate that providing mental healthcare for dental students may be necessary. Though it is not diagnosed to depression by the result of SDS clinical, SDS is used to judge the tendency and the state of depression. As for SDS, there is a role to know the state of depression in a short time for assistance. A clinical diagnosis cannot be done with SDS alone, and judged from a lot of clinical conditions, the life background and life events, etc., in the interview. It seemed that it was necessary to investigate consultation rate to the specialized medical institution and a successive change of the SDS score of each student in future.
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Conclusion The mean SDS score ranged from 43.7 ± 8.5 to 44.8 ± 9.0 between 2006 and 2008 in undergraduates of the Tsurumi University School of Dental Medicine in Yokohama, Japan. ‘‘Diurnal variation,’’ ‘‘personal devaluation,’’ and ‘‘confusion’’ had the highest scores of the 20 individual items of the SDS. It is not possible to obtain a clinical diagnosis only with the SDS; however, in the present study of the SDS, about 30% of dental students showed symptoms of moderate or severe depression, with high scores for ‘‘suicidal rumination.’’ These findings suggest that a need exists for mental healthcare services for dental students.
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