Overall, the lifetime prevalence of depression in the United States is 17 percent, and the one-year prevalence is 10 percent.⁹ People with major depression are at a 4.78 times greater risk of experiencing disability (that is, being unable or less able to work) than are others, and people with minor depression or a mood disturbance are at a 1.55 times greater risk of experiencing a disability than are others.¹⁰ Depression is found about twice as often in women as in men,¹¹ but depression in men also is a serious problem, as highlighted by the National Institute of Mental Health’s "Real Men, Real Depression" campaign.¹² The risk of depression is high enough in the general population to ensure that a significant number of dentists are depressed, regardless of whether depression is related to dentistry as an occupation.

Although dentists would be expected to be at a lower risk of experiencing depression from a demographic standpoint, because depression occurs more often in women and in people of lower income and social status,¹³ the literature on stress and dentistry raises the possibility that, because of heightened stress, dentists may be especially susceptible.

One of us (A.K.) searched MEDLINE and journal bibliographies and found 13 studies that measured depression or other types of emotional distress among dentists since 1980.^{1,3,5,6,14–22} Of these, only five reported dentists’ scores that were above normal.^6,15,18–20 The findings of emotional distress occurred in British,^6,19 Finnish,¹⁵ Australian¹⁸ and South African²⁰ dentists. Thus, the literature reported mixed evidence of dentists’ having high levels of emotional distress, and the evidence that does exist comes from outside the United States. We found no studies that addressed depression in dentists in the United States.

The aim of our study was to identify the relationships between dental specialty and sex and the depression scores of dentists. If occupational stress contributes to depression among dentists, we would expect to find variations in depression levels according to specialty and occupational characteristics, because some specialties may be more stressful than others.

	SUBJECTS AND METHODS

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Sample selection. Our goal in sampling was to collect 50 responses from women and 50 responses from men from each of the following groups: general dentists, endodontists, oral and maxillofacial surgeons, orthodontists, pediatric dentists, periodontists and prosthodontists. The American Dental Association generated a randomly selected list of member dentists who were in practice in the continental United States, stratified according to specialty and sex for this study. We obtained approval for this study from the University of Illinois at Chicago institutional review board.

Data collection. We collected data via a mail survey sent in two waves in June and August 2000. We sent reminder letters two weeks after the initial mailings to maximize the response rate. We mailed a total of 1,050 surveys, and 560 were returned, for a response rate of 53.3 percent. Table 1 shows the number of responses and response rates by specialty and sex. Fewer prosthodontists and orthodontists and more pediatric dentists responded (² = 27.55; 6 degrees of freedom; P < .001). Sex differences in response rates were not significant.

Survey tool. We used a two-page survey to collect demographic and occupational information, data regarding treatment for depression and scores from the Zung Self-Rating Depression Scale (SDS).²³ We also collected data about stress, which will be the subject of a future study. We chose the SDS for this research project because of its ease in completion (only 20 questions) and its comprehensive evaluation of depressive symptoms. The SDS is able to detect 97 percent of depressed people (that is, high sensitivity) and 63 percent of nondepressed people (that is, lower specificity) when compared with the Diagnostic Interview Schedule,²⁴ which is considered the gold standard for psychiatric diagnoses.

In cases in which subjects responded to fewer than 17 items on the 20-item depression scale, we scored the empty items as "missing." If a subject answered 17 or more items but fewer than 20 items, we assigned the mean score to these missing items. Eleven surveys were completed in this manner. Twelve respondents did not answer at least 17 of the depression scale items and, consequently, they received no valid depression score and were not included in the regression analysis.

In addition to administering the depression scale, we gathered information regarding specialty, sex, marital status, number of children, years in practice, location of practice (urban, suburban or rural) and practice type (solo practice, group practice, associate or partner).

	RESULTS

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As shown in Table 2, most of the subjects were married. Respondents exhibited a wide variation in age and years in practice. Women were younger on average, had fewer children (even when controlling for age), were less likely to be married and were less likely to be in solo practice than were men. We found no sex differences in the number of hours worked or in practice location. Specialty groups did not differ by marital status or number of children. Age differed significantly by specialty, with orthodontists and prosthodontists being somewhat older and pediatric dentists being somewhat younger, but post hoc contrasts were not significant.

Missing data. We minimized missing data in the regression analysis in several standard ways. We assumed that the subject had no children if he or she did not provide a number. For age and years of experience, we replaced missing values with the mean values for other subjects of the same sex, specialty and marital status. This allowed us to enter 548 subjects into the regression analysis. We also performed the analysis without replacing the missing data, and the results were almost identical.

Regression model. We entered the following variables into the regression model: sex, years in practice, hours worked per week, age, number of children, location of practice, marital status (single compared with married and divorced/separated compared with married), each specialty compared with general dentistry, general dentistry compared with all specialties, each practice type compared with solo practice, solo practice compared with all others, interaction effects between each specialty and sex, and the interaction effects between each specialty and practice type (compared with solo practice).

We removed all noncontributing variables, and Table 3 shows the remaining, significant variables. However, the final model accounted for only 6 percent of the variance in depression scores, which was statistically significant, but not very useful in understanding the important correlates of depression.

Overall, 47 (9 percent) of 545 dentists had depression index scores of 55 or greater. (According to the SDS, a score of less than 50 indicates normal; 55 to 59, mild depression; 60 to 69, moderate depression; and 70 to 80, severe depression.²⁴) Twenty-eight dentists (5 percent) were moderately or severely depressed (with scores greater than 60). As shown in the figure, only seven (15 percent) of the 47 depressed dentists were receiving treatment, and this percentage did not vary with the severity of depression.

View larger version (46K): [in this window] [in a new window]   Figure. Number of depressed dentists receiving treatment, by sex and severity of depression. The study results showed no significant sex differences in treatment rates.

	DISCUSSION

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In this study, we sought to determine the relationships among sex, specialty, other occupational variables and depression in dentists. The prevalence of depression among dentists may have been artificially low, however, because depressed people may be less likely to respond to surveys than non-depressed people.²⁵ On the other hand, we sampled disproportionately from women, which would tend to result in a higher prevalence of depression.

Prevalence. In general, prevalence rates cannot be determined in this type of study, because the reported prevalence of depression is highly influenced by response bias and the sex makeup of the sample. Determining the true prevalence would require more expensive methods that can track down resistant respondents and minimize response biases. Furthermore, because these data were stratified by specialty and sex, this sample does not reflect the prevalence of depression among dentists in general. Although prevalence issues can be addressed only with caution, these data have sufficient power to contrast sex and specialties, as well as to examine the correlations between experience and hours worked per week and depression. However, the data did not have sufficient power to enable us to examine the influence of sex and specialty within each type of practice.

Demographic factors. The demographic factors that correlated with depression were similar to those we found in national studies.^11,13 Women were depressed at significantly higher rates than were men. Single people were more depressed than married or divorced people. Depression among men in the general population has been reported to be highest among those aged between 55 and 70 years; among women, depression has been reported to be highest among those younger than 35 years.¹³ Our study did not show variations in depression by age.

Sex differences. When we controlled for other factors, sex differences were significant only for pediatric dentists and periodontists, a difference that is normally observed in the general population.^8,11,13 We interpreted this finding to mean that female dentists in the other specialties may be less prone to experiencing depression than are women in general. The sex differences noted among pediatric dentists and periodontists appear to be similar to the sex differences found in the overall population, although a direct comparison is not possible (see preceding discussion concerning prevalence).

Our study results showed that depression did not differ by specialty; this is in contrast to some British literature,^1,21 which reported some specialty differences on other well-being measures. Although hours worked per week have been correlated with distress by some authors,¹ but not others,^3,20 we found no correlation with depression. Similarly, years of experience and practice location were unrelated to depression.

The associations between depression and occupational variables (Table 3) were statistically significant, but the magnitude of the effect on depression scores was small. Other studies^26–28 have had better success in understanding depression among physicians and dentists by examining the internal variables of self-criticism, dependency/passivity and perfectionism. Depression profoundly distorts an individual’s world-view, and often it is more closely related to internal factors than to objective external factors.

Unfortunately, to our knowledge, no national surveys of the general population have been conducted using the Zung SDS,²³ with which we could compare our data. Zung and colleagues²⁴ found a depression rate of 21 percent in nonpsychiatric male outpatients, which is considerably higher than the 9 percent rate we found in this survey.

Table 4 shows the results of our search for all studies conducted after 1980 that addressed depression or any similar construct in any health profession.^{4–6,14,19,22,28–32} Because various measures of depression were used, the rates presented in the table are not directly comparable to those in our study, but they may help put our findings in context. Our study and previous studies, on the whole, did not find high rates of depression in dentists, particularly in the United States. Anxiety, stress or burnout may be more prevalent problems for dentists than is depression.^1,20,21,33

	DEPRESSED DENTISTS AND LACK OF TREATMENT

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Of great concern is the high proportion of depressed dentists (including those with mild depression) who are not receiving treatment for their illness. The low treatment rate among dentists who felt that others would be better off if they were dead is of particular concern, because of the potentially severe consequences of their illness. Generally, depressed people obtain treatment in only 40 percent of cases,^34–36 in spite of the effective treatments available.¹² Because even mild depressive syndromes can be costly in terms of personal suffering, impaired relationships³⁴ and days lost from work,¹⁰ lack of treatment is a significant problem.

Finally, depression has been shown to affect quality of care in physicians.³⁷ Dentists also must be concerned about the effect of depression on the quality of care provided, because depression can be characterized by difficulty in concentrating, difficulty in making decisions and apathy.

Interventions must focus on encouraging depressed dentists to seek treatment. Local and national dental organizations could provide educational and awareness programs that focus on recognizing depressive symptoms, as well as increasing dentists’ knowledge of treatment options. (Editor’s note: The American Dental Association offers Dentist Well-Being Programs, information on which is available at "www.ada.org/prof/resources/topics/wellbeing.asp#handbook".) In addition, educational programs can be presented at national professional meetings. Family members of dentists can receive informational brochures and support through peer-assistance programs. Rada and Johnson-Leong³⁸ recently made the case for assisting depressed dentists.

Future studies should examine the role of internal cognitive styles in stress, anxiety and depression among dentists, as has been done among students²⁶ and physicians.^27,28 Early identification of cognitive styles that may lead to more serious emotional problems also may facilitate the development of prevention programs. In addition, studies of specific specialties that examine the role of sex and practice characteristics in more detail could further clarify whether certain practice characteristics are more conducive to mental health in certain specialties.

	CONCLUSIONS

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The results of this study show that demographic and occupational variables explained less than 6 percent of the variance in depression among dentists. The expected differences in depression between women and men were evident only among periodontists and pediatric dentists. Of particular concern is the low rate of treatment among depressed dentists. Professional organizations and other institutions need to address this problem.