General Hospital Psychiatry 36 (2014) 352–354

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Point prevalence and correlates of depression in a national communitysample with multiple sclerosis☆

Rebecca Viner a, Kirsten M. Fiest a,d, Andrew G.M. Bulloch, Ph.D. a,b,d, Jeanne V.A. Williams, MSc. a,Dina H. Lavorato, MSc. a, Sandra Berzins a,d, Nathalie Jetté, M.D. a,c,Luanne M. Metz, M.D. c, Scott B. Patten, M.D., Ph.D. a,b,d,⁎a Department of Community Health Sciences, University of Calgary, Canadab Department of Psychiatry, University of Calgary, CANADAc Department of Clinical Neurosciences and the Hotchkiss Brain Institute, University of Calgary, Canadad Mathison Center for Mental Health Research & Education, Hotchkiss Brain Institute, University of Calgary, Canada

a b s t r a c ta r t i c l e i n f o

☆ Disclaimer: This research and analysis were based obut the opinions expressed do not represent the views⁎ Corresponding author. Department of Community H

Building, 3280 Hospital Drive NW, Calgary, CANADA, T2(v); fax: +1 403 270 7307.

E-mail addresses: patten@ucalgary.ca, patten@alberta

0163-8343/$ – see front matter © 2014 Elsevier Inc. Alhttp://dx.doi.org/10.1016/j.genhosppsych.2013.12.011

Article history:

Received 23 October 2013Revised 22 December 2013Accepted 24 December 2013

Keywords:Cross-sectional studiesDepressionMultiple sclerosisPrevalencePopulation studiesComorbidity

Objective: The prevalence of depression inmultiple sclerosis (MS) is known tobe elevated, but nearly all availablestudies have estimated period prevalence. The objective of this study was to estimate the point prevalence ofdepression in a representative community sample using the Patient Health Questionnaire, Brief (PHQ-9).Methods: The data source for this study was the Survey of Living with Neurological Conditions in Canada, whichwas derived from a representative sample of household residents.Results: The sample included 630 respondents with MS. With application of the standard PHQ-9 cut point(10+), the prevalence of depression was 26.0% (95% confidence interval 18.9%–33.0%). Depressed subjects hadlower quality of life; an increased frequency of suicidal ideation; and more often reported a negative diseasecourse, high stress, low social support and stigmatization.Conclusions: This study adds to the existing literature by providing point prevalence data: in any 2-week period,about one quarter of community residents with MS experience substantial levels of depressive symptoms.

© 2014 Elsevier Inc. All rights reserved.

1. Introduction

Numerous studies have evaluated the prevalence of depression inclinical samples with multiple sclerosis (MS). Such studies arepotentially flawed by selection bias. Illness severity or evendepression itself may influence health care use in ways that coulddistort such estimates. Only two studies have examined theprevalence of depression in a representative community sample.One, using a short form version of the Composite InternationalDiagnostic Interview [1], reported a 15% annual prevalence of majordepressive episode, approximately three times that of the generalpopulation [2]. Another study employed the Hospital Anxiety andDepression Scale (HADS) in a community sample in SouthernTasmania [3]. Using a cut point of 8+, a prevalence of 18.5% wasreported, approximately twice the reported prevalence in anotherwise comparable non-MS population [3].

n data from Statistics Canadaof Statistics Canada.ealth Sciences, 3rd Floor TRWN 4Z6. Tel.: +1 403-220-8752

healthservices.ca (S.B. Patten).

l rights reserved.

For health services considerations, the most important type ofprevalence is point prevalence: the proportion of a population withdepression at a point in time. Apart from the HADS-based estimatenoted above, there are no population-based point prevalenceestimates for depression in MS.

2. Methods

The opportunity to conduct this analysis arose as a result of a studycalled the Survey of Living with Neurological Conditions in Canada(SLNCC). This was a cross-sectional survey linked to a large, annualgeneral health survey, the Canadian Community Health Survey(CCHS). The CCHS uses a probability sample of approximately 70,000subjects and inquiries about professionally diagnosed long-termmedical conditions. For 2 years (2010 and 2011), the CCHS includedsuch questions for 18 neurological conditions, and participants withaffirmative responses were recruited to participate in the SLNCC.Survey respondents were also asked whether there were householdmembers that had one or more of these neurological conditions, andthose identified were also asked to participate in the SLNCC. SLNCCdata were subsequently collected using computer-assisted telephoneinterviews between September 2011 and March 2012.

The SLNCC sampled the population 15 years and over who werehousehold residents in one of Canada’s 10 provinces. The final

Table 2Characteristics associated with depression prevalence in n=630 SLNCC participantswith MS

OR 95% CI P value

Age category 35–65 yearsa 1.2 0.5–3.3 .66Sex Female 1.4 0.6–3.4 .48Education Less than high school 0.5 0.2–1.1 .09Annual householdincome

b$30,000 2.5 1.1–5.7 .03

Perceived generalhealth

Worse comparedto 1 year ago

3.3 1.6–7.2 .002

HRQoLb HUI b 0.7 9.4 2.9–30.4 b .001HRQoLb HUI b 0 10.2 2.7–38.5 .001Social support Lower quartile 4.8 2.2–10.4 b .001Stress (most days) High 4.2 1.8–9.8 .001Stigma Upper quartile score 6.5 3.0–14.1 b .001

a The baseline category consisted of those b35 or N65.b Health-related quality of life; quantified by the HUI as a preference-weighted

health utility. A score of less than zero indicates a health state associated with apreference lower than death.

353R. Viner et al. / General Hospital Psychiatry 36 (2014) 352–354

sample consisted of 8200 people with neurological conditions. Theestimated response rate was 81.6% [4]. Standard items were used toassess age, sex, level of education and household income. Therewere also general health items, perceived stress items and brief(four-item) scales assessing social support and stigma. The stigmaitems referred specifically to MS (e.g., “Because of my multiplesclerosis, some people avoidedme.” The Health Utility Index, Mark III(HUI3) [5] was also included. This is a quality-of-life scale providingutility-weighted ratings for individuals’ overall health status, asassessed through eight dimensions. HUI3 scores less than b0.70 aregenerally regarded as providing evidence of severe disability [6]. Toassess depression, the Patient Health Questionnaire, Brief (PHQ-9)was included [7]. This scale has nine items, each scored 0–3, for a totalpossible score of 27, with an optimal cut point of ≥10. Unlike otherdepression rating scales, the PHQ-9 items align with those of theDiagnostic and Statistical Manual of Mental Disorders, Fourth Edition,‘A’ criteria for major depression. The full questionnaire, including allof the measures mentioned above, is available on the StatisticsCanada Website [4].

In order to account for survey design effects such as clustering andunequal selection probabilities, the use of replicate sampling weightsand bootstrapped variance estimation are recommended by StatisticsCanada [4]. The replicate weights (n=500) also include adjustmentsfor nonresponse and “out of scope” (e.g., subjects excluded becausethe reported diagnosis could not be confirmed) status. The set ofreplicate bootstrap sampling weights used in this analysis was thatdeveloped for the SLNCC by Statistics Canada. The odds ratio (OR) wasused to examine depression correlates.

3. Results

There were 630 SLNCC respondents with MS. They were 73.3%female, and the mean age was 51.8 years. Additional descriptiveinformation is provided in Table 1. The respondents reported a meanage of MS onset of 37.0 years. The mean number of years sincediagnosis with MS was 14.8, and the mean number of years sincesymptom onset was 18.8.

The overall prevalence of depression according to the PHQ-9 cutpoint (≥10) was 26.0% [95% confidence interval (CI) 18.9–33.0]. ThePHQ-9 can also be scored using an algorithm that reflects diagnosticcriteria [7]. It requires endorsement of the two obligatory symptoms, atotal of five symptoms endorsed at least “most of the time” or suicidalideation at the “several days” level. According to the algorithm, theprevalence was 11.9% (95% CI: 5.9–18.0). The remainder of the reportuses cut point derived frequencies.

Table 1Characteristics of (n=630) SLNCC respondents with MS

Estimate 95% CI

Age (mean) 51.8 49.3–54.3Sex

Male 26.7% 19.5–33.8Female 73.3% 66.2–80.5

Education levelHigh school graduate or less 37.1% 31.1–43.2Greater than high school graduation 62.9% 56.8–68.9

Annual household incomeLess than $30,000 24.7% 18.7–30.6Greater than $30,000 75.3% 69.4–81.3

Self-perceived general healthGood/very good/excellent 64.4% 57.6–71.2Fair/poor 35.6% 28.8–42.4Suicidal ideationa 8.9% 5.2–12.6HUI (b0.7) 58.7% 51.1–66.2

a Based on item 9 of the PHQ-9; indicates suicidal ideation on several days in thepreceding 2 weeks.

Table 2 presents associations with other variables. No significantage or sex differences were observed. Associations were seen forseveral depression risk factors or impacts: low social support, highstress, perceived stigmatization and lowhousehold income. Amajorityof respondents fell into the low-HUI3 category (see Table 1).Depression was nevertheless strongly associated with low quality oflife (Table 2).

4. Discussion

These results confirm the markedly elevated prevalence ofdepression in MS and more negative health status associated withdepression. Previous Canadian population-based estimates using thePHQ-9 reported much lower prevalence in the general population:8.4% for the cut point and 3.3% for the algorithm scoring [8].Irrespective of the scoring strategy used, the prevalence remainsapproximately three times higher than that of the general population,consistent with previous annual prevalence data [2], whereas thepoint prevalence estimate of Wood et al. using the HADS wasapproximately twice that of the general population. The prevalence ofsuicidal ideation was high in this sample at 8.9%. A previous Canadianpopulation survey using the PHQ-9 [8] found a 2.8% (95% CI 2.3–3.4)frequency of endorsement.

Causal inferences cannot be made from this cross-sectional data.Striking associations between depression and perceived health, qualityof life, income, social support, stress and stigma were observed. Suchvariablesmay causeor be caused by depression. The response rate in theSLNCC was good (N80%), but nonresponse may nevertheless haveaffected the prevalence estimate. Concerns have been expressed that anoverlap of symptoms between depression and MS could lead to false-positive ratings. However, the PHQ-9 appears to performwell in peoplewith MS [9], supporting the validity of these estimates.

References

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