Part IV: Who will benefit from preventive care?

Transcription

1 Part IV: Who will benefit from preventive care?

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3 Chapter 6 Conversion of subclinical depressive symptoms into depressive disorders This chapter is submitted as: Van Zoonen, K., Kleiboer, A. M., Beekman, A. T. F., Smit, J. H., Boerema, A. M., Dijkshoorn, H., Cuijpers, P. (2014). Predictors of the conversion of subclinical depressive symptoms to major depressive and anxiety disorders in the community. Manuscript submitted for publication to Depression & Anxiety.

4 114 Chapter 6 Abstract Background: Subclinical depression is an important predictor of developing a fullblown depressive disorders. However, it is not known which people with a subclinical depression will develop a full-blown depression and which people will not. The current study examined predictors of the onset of depression (major depression and dysthymia) in people with subclinical depressive symptoms over a one year period. Since anxiety disorders frequently co-occur, we also explored predictors of the onset of anxiety disorders. Methods: 162 people with subclinical depressive symptoms were recruited from the general population. They were eligible to participate if they were aged 18 years or older, scored 20 or higher on the K10 screening instrument for depression and did not meet criteria for a current depressive disorder (dysthymia or major depression) as established by a diagnostic interview; the Composite International Diagnostic Interview(CIDI). A total of 139 people (86%) completed the CIDI diagnostic interview at one year follow-up. Results: 31 respondents (22%) developed a depressive disorder within one year and 20 respondents (14%) developed an anxiety disorder. At baseline 35 respondents (22%) met criteria for an anxiety disorder. Lifetime history of depression predicted the onset of a depressive disorder within one year, whereas severity of symptoms predicted the onset of anxiety disorders. Conclusions: Professionals should be vigilant for people with subclinical depression who report prior depression and/or anxiety disorders, or indicate more severe symptoms on a screening instrument. It is important to further examine possible predictors of depressive disorders in people that are at high risk.

5 Conversion of subclinical depressive symptoms into depressive disorders 115 Introduction Depression affects millions of people worldwide with one in every eight men and one in every 5 women experiencing a depressive disorder once in their lives (1, 2). It is becoming the single leading cause of disease burden and is associated with significant loss in quality of life (3, 4). It is well known that people who suffer from subclinical depression are at high risk of developing a depressive disorder (5, 6). Subclinical depression is seen as a prodromal phase of major depression and can be defined as a score above the cut-off on a screening instrument, but failing to meet the criteria for major depression according to the Diagnostic and Statistical manual of Mental Disorders V (DSM-V) (6-8). The incidence rates of subclinical depression depend on the definition and population used and vary between 2.2% and 24% (9). Research has shown that preventive interventions are able to prevent the onset of depression (10, 11). Although research on who will develop a major depression is scarce, certain risk factors have been identified in preventing depression (12). These risk factors can be divided into two classes: specific factors, such as severity of symptoms, and nonspecific factors, such as poverty (13). Studies focusing on the onset of depression in people with subclinical depression have shown that specific factors, such as severity of depressive symptoms, family history of depression, feelings of worthlessness or guilt, suffering from chronic illnesses, and mastery are important (8, 14-16). Furthermore, a need for care (e.g. met need, unmet need, or no perceived need) might be important in predicting who will develop a depressive disorder. Most people with mental health problems believe they do not need treatment, because the symptoms are temporary or not serious enough (17). The first aim of the current study was to identify which people with a subclinical depression had developed a depressive disorder within one year. Since depression and anxiety often co-occur we also examined the onset of anxiety disorders at baseline and one year follow-up. A second aim was to examine what predicts (e.g. severity of symptoms, mastery, lifetime history of depressive and/or anxiety disorders, chronic illness, perceived need for care, loneliness, and demographic factors) the onset of depression or an anxiety. 6 Materials and Methods Design A longitudinal cohort study was conducted in people from the general population where people with subclinical depressive symptoms were followed during a one year period to see if they developed a depressive disorder.

6 116 Chapter 6 Participants, recruitment and procedure Participants in the general population were recruited in collaboration with Municipal Health Services (GGD) in three different areas in the Netherlands. The current study joined the national Health Survey 2012 of the GGD. In the selected areas preventive interventions were widely advertised and available to everyone. More details can be found elsewhere (18). Recruitment at baseline took place between September 2012 and February Follow-up measures one year later. People were eligible to take part when they scored 20 or higher on a screening instrument, Kessler 10 (K10) (19, 20) and were 18 years or older. If permission was granted people received a letter containing information about the current study including the follow-up. Participants with insufficient understanding of the Dutch language, either spoken or written, were excluded. To establish depression status at baseline and follow-up, participants were contacted by telephone for a diagnostic interview, the Composite International Diagnostic Interview (CIDI, 2.1) (21). When the criteria for major depression and/or dysthymia were met participants remained in the study, but were not included in the current paper. Participants received an online questionnaire covering several domains including health care use and perceived need for care. At baseline this questionnaire was followed by a short questionnaire on people s knowledge of preventive interventions and mental health care. This questionnaire was conducted by telephone since some questions needed some more elaboration and explanation by the researchers. A total number of 162 respondents with subclinical depression were included at baseline. Instruments Demographics In the current study marital status, educational level, employment status, gender and age were used as demographic variables. Diagnostic interview The CIDI was conducted at baseline and follow-up to establish which participant met the criteria for major depression and/or dysthymia. The current study used the lifetime version of the CIDI and two sections were administered; the anxiety (section D) and the depression section (section E). It has shown adequate validity and excellent reliability for depressive disorders (22). The interviews were conducted by trained Master level students in Clinical Psychology who received 8 hours of training and worked under supervision.

7 Conversion of subclinical depressive symptoms into depressive disorders 117 Depressive symptoms To examine the severity of symptoms the K10 was used (19). This screener consists of 10 questions and is mostly focused on depressive symptoms (20). The questions are answered on a 5-point rating scale from never (1) to always (5). The Dutch version has shown good psychometric properties (20). The baseline scores on the K10 were derived from the Health Survey of the GGD. Perceived need for care The three categories of need for care at baseline were established using a combination of items from the Trimbos/iMTA questionnaire (TiC-P) and items from a short telephone questionnaire were used. The TiC-P measures health care uptake associated with psychiatric illness (23). A met need, or people who received professional care, in the 6 months prior to baseline were assessed with the TiC-P. Unmet need and no perceived need were established with the short telephone questionnaire, after people reported no experience with professional care on the TiC-P. Respondents who indicated they would have used preventive interventions if they had known about them were considered having an unmet need. Respondents who reported to be unwilling to use preventive interventions were considered having no perceived need. Chronic illness To examine who suffered from a chronic illness in the past 12 months before baseline we used data derived from the GGD-survey. Questions stated if people reported one of the following 19 (chronic) diseases; any form of cancer, diabetes, several types of heart diseases, stroke, severe back problems, COPD and asthma, migraines, involuntary loss of urine, chronic eczema, psoriasis, dizziness with falling, arthrosis, and chronic or severe elbow, wrist or hand problems. When respondents had answered yes on 1 or more questions they were considered to suffer from a chronic illness. 6 Loneliness Loneliness was assessed using the Jong Gierveld Loneliness scale (24). The data were derived from the survey of the GGD. The GGD dichotomized the outcome so respondents either experienced loneliness or they did not. The scale has proved to be a reliable and valid instrument (25). Mastery Mastery (e.g. to what extent respondents felt they had control of their life and life-events) was examined by using the short form of the Pearlin Mastery Scale (26). Questions were answered on a 5-point rating scale from strongly agree to strongly disagree. The total score has a range of 5 to 25. Lower scores indicate a more external locus of control

8 118 Chapter 6 and higher scores indicate a more internal locus of control. The internal consistency was good (α =.83). Statistical Analysis To determine how many people had developed a major depression and/or dysthymia or an anxiety disorder between baseline and follow-up descriptive statistics were used. Univariate and multivariate logistic regression analyses were conducted to examine the influence of different baseline characteristics (e.g. severity of symptoms, mastery, lifetime history of depressive and/or anxiety disorders, chronic illness, loneliness, perceived need for care and demographic factors) on depression status and anxiety status within one year after baseline. Results Sample After filling out the national Health Survey a total of 1191 people with depressive disorders as well as subclinical depressive symptoms were invited to take part in the study. Three hundred and thirty three people (28%) returned their informed consent of whom 291 respondents (24%) completed the diagnostic interview. Reasons for not completing the diagnostic interview were; physical or mental inabilities (e.g. stroke, psychological stress), insufficient knowledge of the Dutch language, no response, lack of motivation to participate, emigration to a foreign country, lack of time, or no given reason. Another 106 participants were excluded due to meeting the criteria for a depressive disorder, leaving a total of 185 participants with subclinical depressive symptoms of which 162 participants completed all the information at baseline. At follow-up 139 participants (86%) completed the diagnostic interview. Reasons for not completing were; psychological distress (n = 3), no time or not in the mood (n = 3), dissatisfaction with the interview (n = 2), none response (n = 12), or death of the respondent (n = 3). Table 1 shows the descriptive characteristics of the participants at baseline and follow-up. Age ranged widely from 19 to 94 years, with an average age of 57 (SD = 18) at baseline. Most respondents were female (56%), in a relationship (57%), did not have a paid job (59%), and did not perceive a need for care (40%). Furthermore, most respondents did not suffer from a comorbid anxiety disorder at baseline (78%). Table 2 shows the characteristics of the predictors of the onset of depression or anxiety within a year.

9 Conversion of subclinical depressive symptoms into depressive disorders 119 Table 1. Descriptive characteristics of respondents with and without depression or anxiety between baseline and follow-up. Baseline Between baseline and follow-up Gender, n (%) Female Male Total Respondents n = (56.2) 71 (43.8) Depressive disorder n = (58.1) 13 (41.9) No depressive disorder n = (55.6) 48 (44.4) Anxiety disorder n = (80) 4 (20) No Anxiety disorder n = (52.1) 57 (47.9) Age, M (sd) 57.2 (17.8) 54.0 (13.2) 58.4 (18.1) 54.2 (17.8) 57.9 (17.1) Marital Status, n (%) In relationship Single 93 (57.4) 69 (42.6) 16 (51.6) 15 (48.4) 61 (56.5) 47 (43.5) 9 (45) 11 (55) 68 (57.1) 51 (42.9) Education, n (%) Low Middle High 24 (14.8) 81 (50.0) 57 (35.2) 3 (9.7) 17 (54.8) 11 (35.5) 17 (15.7) 50 (46.3) 41 (38.0) 1 (5) 13 (65) 6 (30) 19 (16) 54 (45.4) 46 (38.7) Employment status, n (%) Paid job No paid job 66 (40.7) 96 (59.3) 16 (54.6) 15 (48.4) 43 (39.8) 65 (60.2) 10 (50) 10(50) 49 (41.2) 70 (58.8) 6 Onset of depression between baseline and follow-up At follow-up 58 respondents (41%) scored below the cut-off score on the K10 and 82 respondents scored (59%) scored above the cut-off score. Between baseline and followup, a total of 31 respondents (22%) met the criteria for a depressive disorder and 108 respondents (78%) did not. However, 33 respondents (24%) suffered from a comorbid anxiety disorders at baseline and 9 respondents (27%) developed an anxiety disorder at baseline. On the other hand, most respondents (n=106, 76%) did not suffer from a comorbid anxiety disorder at baseline. Of these 106 respondents, 22 respondents (21%) developed a depressive disorder between baseline and follow-up. Figure 1 shows these results in a flowchart.

10 120 Chapter 6 Depressive disorder (n = 22; 20.8%) Subclinical depression (n = 106; 76.3%) Anxiety disorder (n = 9; 7.1%) Comorbid depression and anxiety (n = 6; 5.7%) Sample (n = 139 No depression or anxiety (n = 69; 65.1%) Depressive disorder (n = 9; 27.3%) Subclinical depression and anxiety disorder (n = 33; 23.7%) Anxiety disorder (n = 11; 33.3%) Comorbid depression and anxiety (n = 5; 15.2%) No depression or anxiety (n = 8; 24.2%) Figure 1. Flowchart of diagnosis within a year in respondents with and without anxiety disorders at baseline Since the only information on depressive symptoms was measured at baseline and follow-up and the diagnostic interview measures the entire year between baseline and follow-up, there is no way to determine the actual recovery of respondents. Interestingly, 7 respondents (16%) who reported a met need, 14 respondents (45%) who reported an unmet need, and 10 respondents (16%) without a perceived need had developed a depressive disorder. However, these differences were not significant. Table 2 presents the characteristics of the predictors of the onset of depression.

11 Conversion of subclinical depressive symptoms into depressive disorders 121 Table 2. Characteristics of predictors of the onset of depressive and/or anxiety disorders between baseline and follow-up. Perceived need, n (%) Met Need Unmet Need No perceived need Depressive disorder n = 31 7 (22.6) 14 (45.2) 10 (32.3) No Depressive disorder n = (28.7) 29 (26.9) 48 (44.4) Anxiety disorder n = 20 9 (45) 6 (30) 5 (25) No anxiety disorder n = (24.4) 37 (31.1) 53 (44.5) Comorbid anxiety at baseline, n (%) Yes No 9 (29) 22 (71) 24 (22.2) 84 (77.8) 11 (55) 9 (45) 22 (18.5) 97 (81.5) Lifetime depression, n (%) Yes No 20 (64.5) 11 (35.5) 43 (39.8) 65 (60.2) 13 (65) 7 (35) 50 (42) 69 (58) Loneliness, n (%) Yes No 21 (67.7) 10 (32.3) 73 (67.6) 32 (29.6) 15 (75) 5 (25) 79 (66.4) 37 (31.1) Chronic illness, n (%) No illness 1 or more illnesses 4 (12.9) 24 (77.4) 19 (17.6) 69 (63.9) 3 (15) 16 (80) 20 (16.8) 77 (64.7) 6 Mastery, M (sd) 9.5 (4.4) 10.7 (4.3) 6.5 (4.1) 10.6 (4.3) Severity of symptoms, M (sd) 25.7 (4.6) 24.9 (5.0) 28.0 (5.0) 24.6 (4.7) a = not applicable Univariate associations between baseline predictors and depression status within a year No significant association were found between perceived need, demographic factors, loneliness, mastery, chronic illness, or severity of depressive symptoms and the development of a depression within a year (Table 3). However, a significant association was found for lifetime history of depression and onset of depression. People with a previous diagnosis of depression were 2.79 times more likely to have developed a depression within a year (OR = 2.79; 95% CI = ; p<.05). Multivariate associations between baseline predictors and depression status within a year A multivariate logistic regression was conducted to examine what factors best predicted the onset of a depressive disorder (Table 3). In line with the univariate analyses, people with a previous episode of depression or anxiety were 3.26 times more likely to develop a major depression than those without a previous episode of depression (OR = 3.26; 95% CI = ). The model was a good fit to the data, (χ 2 (8) = 7.71, p =.46). However, the model only explained a modest portion of the variance (Nagelkerke R 2 =.19).

12 122 Chapter 6 Onset of anxiety between baseline and follow-up A total of 33 respondents (24%) of the 139 met the criteria for anxiety disorders at baseline and 11 respondents (33%) also met criteria for anxiety disorders at follow-up (See Figure 1). Only 9 respondents (7%) of the respondents who suffered only from subclinical depression (76%) at baseline developed an anxiety disorder within a year. Furthermore, of the 33 respondents with comorbid anxiety at baseline 5 (15%) also reported comorbid depression and anxiety between baseline and follow-up compared to 6% of the respondents who only suffered from subclinical depression. Univariate associations between baseline predictors and anxiety status within a year Results of the univariate logistic regression analysis showed significant effects for gender (χ 2 (1) = 5.84, p<.05), comorbid anxiety disorder at baseline (χ 2 (1) = 10.91, p<.01), and severity of symptoms (χ 2 (1) = 7.47, p<.01) on the onset of anxiety (Table 3). Furthermore, lifetime diagnosis of depression showed a trend (χ 2 (1) = 3.66, p=.06). Females were 3.68 times more likely to develop an anxiety disorder within a year than males (OR = 3.68; 95% CI = ), people who reported more severe symptoms are 1.13 more likely to develop an anxiety disorder than respondents who reported less severe symptoms (OR = 1.13; 95% CI = ), and respondents who suffered from comorbid anxiety disorder at baseline were 5.39 times more likely to develop an anxiety disorder within a year compared to respondents who do not suffer from comorbid anxiety disorder (OR = 3.68; 95% CI = ). Furthermore, respondents who reported a lifetime history of depression were 2.56 more likely to develop an anxiety disorder within one year (OR = 2.56; 95% CI = ). Multivariate associations between baseline predictors and anxiety status within a year A multivariate logistic regression was conducted to investigate what factors best predicted the onset of an anxiety disorder within one year (Table 3). Respondents who reported more severe symptoms on the K10 were 1.15 more likely to develop an anxiety disorder (OR = 1.15; 95% CI = ). The model was a good fit to the data (χ 2 (8) = 5.51, p =.70). The model explained 30% of the variance (Nagelkerke R 2 =.30).

13 Conversion of subclinical depressive symptoms into depressive disorders 123 Table 3. Predictors of the onset of depression and anxiety. Depression Anxiety Univariate Multivariate Univariate Multivariate Predictor OR (95% CI) OR (95% CI) OR (95% CI) OR (95% CI) Gender 1.11 ( ) 1.21 ( ) 3.68 ( )* 3.81 ( ) Age 0.99 ( ) 1.01 ( ) 0.99 ( ) 1.00 ( ) Marital status 0.82 ( ) 0.81 ( ) 0.61 ( ) 0.88 ( ) Educational level a 3.06 ( ) 2.05 ( ) 4.57 ( ) 2.48 ( ) 3.40 ( ) 1.87 ( ) 1.93 ( ) 1.52 ( ) Middle High Employment status 0.62 ( ) 0.64 ( ) 0.70 ( ) 0.52 ( ) Perceived need for care b Unmet need 0.35 ( ) 0.71 ( ) 0.52 ( ) 0.30 ( ) 2.12 ( ) 1.49 ( ) 2.14 ( ) 0.92 ( ) No perceived need Loneliness 0.92 ( ) 0.54 ( ) 1.41 ( ) 1.65 ( ) Chronic illness 1.65 ( ) 1.66 ( ) 1.39 ( ) 2.47 ( ) Lifetime depression 2.79 ( )* 3.26 ( )* 2.56 ( ) 1.66 ( ) Comorbid anxiety disorder at baseline 1.43 ( ) 0.64 ( ) 5.39 ( )** 2.36 ( ) Severity of symptoms 1.04 ( ) 1.02 ( ) 1.13 ( )** 1.15 ( )* Mastery 0.93 ( ) 0.89 ( ) 0.94 ( ) 1.06 ( ) a = reference category is low ; b = reference category is met need *p<.05; **p<.01 6

14 124 Chapter 6 Discussion People with subclinical depression are at high risk of developing a depression (6, 27), but what predicts the onset of depression is unknown. In order to be able to predict who is most in need of preventive care, it is important to examine predictors of the onset of depression in people with subclinical depression. Therefore, the current study has focused on the onset of depressive disorders in a one year period. Since anxiety often cooccurs with depression the current study also explored predictors of anxiety (28). At follow-up 22% had developed a depressive disorder (dysthymia and/or major depression) within a year after baseline and 12% had developed an anxiety disorder. Incidence rates of major depression in people with subclinical depression varied widely across studies, from 0.15 in general population studies to 0.58 in high-risk studies (6). However, our results show lower incidence rates in a high-risk sample. People with a lifetime history of depression were more likely to develop a depressive disorder. This is in line with previous studies (6, 27). Furthermore, being female, reporting more severe depressive symptoms, and having a comorbid anxiety disorder at baseline increases the risk of developing an anxiety disorder within one year. However, multivariate analysis only showed higher severity of symptoms predicted the onset of anxiety within a year. The current study emphasizes the importance of lifetime history of depression and severity of symptoms on the onset of depression and anxiety, but could not identify other predictors. It remains difficult to predict the onset of depression (or anxiety) in a high-risk sample. However, the current results support the notion of a depression continuum (29-31). The results should be interpreted in light of some limitations. The current study had a low response rate. Low response rate, unfortunately, is not uncommon in general population research (32). They propose that the general population is contacted more often for (commercial) research and so people tend to be more reluctant in wanting to participate. However, this has probably led to a selection bias due to the design of the current study. First, the GGD Health Survey reported a selection bias due to underrepresentation of the lower age groups between 18 and 49 years, men, and immigrants (33). Furthermore, not everyone who completed the Health Survey gave permission to be contacted for further research. This might have contributed to selection bias further. Second, the number of respondents in the current study is relatively small and might have limited the power to find an effect. Finally, although the screener K10 is not a pure measure for depressive symptoms, it has shown to adequately identify depressive symptoms and disorders (20). There are some strengths to this study as well. It is one of the very few studies that has examined subclinical depression in the general population and the drop-out rate

15 Conversion of subclinical depressive symptoms into depressive disorders 125 between baseline and follow-up was low (14%). This is encouraging for populationbased research that is known to struggle with response and drop-out rates. Another strength is the two-step design. In the first step people with a score above the cut-off on a screener were included and the second step excluded people with a depressive disorder diagnosis according to a diagnostic interview. This makes the current study a unique, first step in identifying predictors of the onset of depression (and anxiety) in a high-risk sample in the general population. Although the variance explained was relatively small, our results in combination with previous research show that it is important that professionals in mental health care examine and take into account people s history of depression (and anxiety). They should be vigilant for people who report previous episodes of depression and/or anxiety. Future research should further examine perceived need for care in a larger sample, since the lack of differences between the need categories in this study might be due to the low sample sizes. Conclusion Although the current study has shown it might be difficult to predict who will develop a depressive or anxiety disorder in a high risk sample, it is important to continue to identify possible predictors in the onset of depressive and anxiety disorders. Increasing insight will make it possible to tailor and attune preventive care to people who are at risk and will benefit from it. The current study supports the findings from previous research indicating that people that have suffered from a previous depressive disorder are most likely to develop another full-blown depression. Furthermore, severity of symptoms is important in predicting the onset of anxiety. It is important to try and replicate these results in future research. 6

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