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Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Objective

To evaluate the prevalence, correlates, and subgroups at highest risk for suicidal ideation among adults with arthritis.

Methods

We used data on US adults with arthritis, ages ≥40 years, participating in the 2007–2008 National Health and Nutrition Examination Survey. Suicidal ideation was assessed by item 9 of the Patient Health Questionnaire 9 (PHQ-9). Sociodemographic factors, health behaviors, and comorbid conditions were examined as potential correlates. Depression was measured by the PHQ-8 score (range 1–24). We used random forests to identify subgroups at highest risk for suicidal ideation. To determine if any correlates were unique to arthritis, we compared results to those for persons with diabetes mellitus and cancer.

Results

The prevalence ± SEM of suicidal ideation was 5.6% ± 0.8% among persons with arthritis and 2.4% ± 0.4% among those without. The most important correlates for suicidal ideation in adults with arthritis were depression, anxiety, duration of arthritis, age, income:poverty ratio, number of close friends, pain, alcohol, excessive daytime sleepiness, and comorbidities. Eleven of the 16 most important contributors for suicidal ideation among adults with arthritis were also important for people with diabetes mellitus and cancer. Among persons with arthritis, subgroups at highest risk for suicidal ideation were those with a PHQ-8 score between 18 and 24 and less than 4.5 years of arthritis (96.5%), and those with a PHQ-8 score between 7 and 17, ≥1.24 days of binges/month, and either an income of ≥$45,000/year (85.4%) or an income of <$45,000/year and >3 comorbidities (70.8%).

Conclusion

Depression, short duration of arthritis, binge drinking, income, and >3 comorbidities identified subgroups of adults with arthritis at greatest risk for suicidal ideation.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Suicide is one of the highest public health priorities worldwide (1). The World Health Organization objectives for suicide prevention emphasize identification of high-risk groups (2). Suicidal ideation, referring to wishes that one's life would end or thoughts of harming or killing oneself, represents an important phase in the suicidal process and often precedes suicidal attempts or completed suicide (3, 4). Patients with chronic medical illnesses and especially those experiencing pain are more likely to report suicidal thoughts (5, 6). As a chronic condition frequently associated with pain, arthritis may increase the risk of suicidal ideation. Coping with the effects of arthritis on a daily basis can have detrimental consequences for the mental health of those affected.

Little is known about the occurrence of suicidal ideation among persons with arthritis (7, 8). One study showed that almost 11% of outpatients with rheumatoid arthritis (RA) experienced suicidal thoughts at the time of the study (7). However, the sample was small and was focused on RA, which represents only part of the arthritis population. Another study using a survey-based sample showed that suicidal ideation was approximately twice as common among adults with arthritis as those without (8). However, the association between arthritis and suicidal ideation in the general population, and whether arthritis differs from other chronic disorders in this association, remains poorly characterized. Most importantly, the subgroups of adults with arthritis at greatest risk for suicidal thoughts are not known. Suicidal ideation is the result of a complex set of interactions between predisposing factors, buffers, and more acute situational events. Focus on subgroups at high risk can help improve suicide prevention and intervention strategies in persons with arthritis.

To address these questions, we used data from the National Health and Nutrition Examination Survey (NHANES) for 2007–2008, the largest US survey that included questions about both suicidal thoughts and arthritis and related conditions such as pain. The purpose of this study was to determine the prevalence of suicidal ideation among adults with arthritis, and to identify subgroups of individuals with arthritis at greatest risk for suicidal thoughts. Additionally, to evaluate if the most important correlates among persons with arthritis differ from those of people with other chronic diseases, we compared results with those of people with diabetes mellitus and cancer.

Significance & Innovations

  • To our knowledge, this is the first population-based US study of suicidal ideation in adults with arthritis.

  • We identified subgroups of people with arthritis at highest risk for suicidal ideation.

  • The main correlate was depression, which was assessed by the Patient Health Questionnaire 8.

  • Similar risk factors were found in the diabetes mellitus and cancer groups.

MATERIALS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Data source.

We examined publicly available data from the NHANES 2007–2008, a cross-sectional population-based survey of the US noninstitutionalized civilian population (9). Participants underwent a home interview that included information on demographic characteristics, health behaviors, medical conditions, depression, and social situation.

Depression and suicidal thoughts were assessed in participants ages 20 years or older who participated in the examination component. Because measures of social support were only obtained in those ages 40 years or older, and because most persons with arthritis were also older, we limited our analyses to subjects ages 40 or older. The sample included 3,863 persons (response rate of 69.1%). Of these, 7 persons had missing data on arthritis and 371 had missing data on the entire Patient Health Questionnaire 9 (PHQ-9) questionnaire, either because they had proxy respondents, ran out of time, or refused or did not provide an answer.

Subjects with arthritis, diabetes mellitus, or cancer.

We selected subjects with arthritis based on self-reported physician-diagnosed arthritis, as ascertained by the question, “Has a doctor or other health professional ever told you that you had arthritis?” Self-reports of arthritis are considered to have sufficient validity for surveillance purposes (10). For comparison, we also examined 2 other representative chronic diseases, diabetes mellitus and cancer (excluding nonmelanoma skin cancers), which were ascertained through questions similar to that above. Since a recent diagnosis of cancer is more likely to be associated with depression or suicidal thoughts (11, 12), we limited the analysis of this group to those diagnosed in the 2 years preceding the survey.

Outcome.

We used suicidal ideation, assessed by item 9 of the PHQ-9, as the outcome variable. The PHQ-9 is a 9-item screening instrument with high reliability and validity in the general population that evaluates the frequency with which depressive symptoms are present over the prior 2 weeks (13). Item 9 asks, “Over the last two weeks, how often have you been bothered by the following problem: thoughts that you would be better off dead, or of hurting yourself in some way?” Possible responses were “not at all,” “several days,” “more than half the days,” or “nearly every day.” For analysis, we categorized the responses as not present (0) or present at any frequency (1).

Item 9 of the PHQ-9 has been used by many studies assessing suicidal ideation; however, it does not ask specifically about thoughts of attempting suicide (14, 15). Use of a more specific item, such as the suicidal intent item of the Beck Depression Inventory (16), is more likely to lead to nonresponse.

Correlates.

Sociodemographic factors.

Based on a review of the literature, the following sociodemographic factors were examined as potentially predisposing to suicidal ideation: age (continuous variable), sex, ethnic origin (white, African American, Hispanic, other), nativity (US versus other), education level (less than high school diploma, high school diploma, some college without degree, college degree or higher), marital status (never married, married, divorced/separated, widowed), social support, annual household income, ratio of income to the federal poverty level (continuous variable), food security, presence of health insurance, presence of a usual source of health care, and mental health care visit in the past year.

Food security was used as an additional measure of poverty and evaluated by a validated 10-item scale (17). We examined 3 items of social support: emotional support (count on anyone to provide you with emotional support), instrumental support (count on anyone to provide you with financial support), and social network (number of close friends or relatives). Responses to the first 2 items were coded as present or absent.

Health behaviors and comorbid conditions.

Smoking, alcohol use, and illicit drug use are among the health behaviors more frequently associated with suicidal thoughts (1). Smoking status was classified as never, former, or current smoker. For current smokers, the number of cigarettes per day was assessed. Alcohol use was evaluated by 2 questions: days of drinking per month (“In the past 12 months, how many days per month did you drink?”) and days of binges per month (“How many days per month did you have 5 or more drinks in a single day?”). Illicit drug use was assessed by 2 variables examining current use of marijuana and current use of other illicit drugs (cocaine, heroin, or methamphetamine).

We included as comorbid conditions heart disease (coronary disease, myocardial infarction, angina, or chronic heart failure), stroke, hypertension, pulmonary disease (chronic bronchitis, emphysema, or asthma), liver disease, diabetes mellitus, and cancer. The number of comorbid conditions (range 0–7) was also evaluated.

Depression, anxiety, and sleep disturbances were also included because they have been associated with suicidal ideation (1). Depression was evaluated by the PHQ-8 score (possible range 0–24), removing the question pertaining to suicidal ideation from the PHQ-9 (18). A score of 10 or higher was used for the diagnosis of depression. Anxiety was assessed by a question on “days felt worried, tense, or anxious during the past month.” We used 3 measures of sleep disturbance (19): physician-diagnosed insomnia, short sleep duration (<6 hours of sleep per night), and excessive daytime sleepiness (never, rarely = 1 time a month, sometimes = 2–4 times a month, often = 5–15 times a month, and almost always = 16–30 times a month).

Pain was assessed by the following question: “During the past 30 days, how many days did pain make it hard for you to do your usual activities?” Physical disability was assessed by questions examining limitations in 4 activities of daily living (ADL): getting in or out of bed, dressing, eating, and walking, and 1 question addressing the use of special equipment because of a health problem. Responses to questions on limitations in ADL were coded as 1 = no difficulty, 2 = some difficulty, 3 = much difficulty, and 4 = unable to do. We also constructed a dichotomous measure of “unable to do” at least 1 of 4 ADL.

Statistical analysis.

For descriptive analyses, we used methods to account for the complex sampling strategy of the NHANES 2007–2008. We also used sample weights to adjust SEMs for selection and nonresponse, and to provide nationally representative results from the surveyed samples. Analyses were based on samples of 1,545 persons with arthritis, 672 with diabetes mellitus, and 127 with cancer diagnosed in the preceding 2 years. Persons with missing data were included as a subpopulation so their influence on SEMs could also be captured. Descriptive analyses were performed using SAS, version 9.2.

We used random forests to identify and validate the most influential correlates for suicidal ideation. A random forest is an ensemble classification method that combines the results of multiple classification trees (20). A classification tree is a nonparametric, non–model-based, hierarchical classification procedure that uses recursive partitioning to identify the variables that best subset patients into groups with a higher and lower prevalence of the outcome. The classification tree procedure first identifies the independent variable (i.e., the predisposing variable noted above) that best separates those with higher from those with lower prevalence of suicidal ideation. The procedure is then repeated for each resulting subgroup until subgroups of sufficient purity are obtained. Variables higher in the tree are more influential than those lower in the tree. Because subgroups are sequentially derived, the importance of a single variable in correctly classifying a group of people is conditional on earlier variables in the tree. In this way, classification trees naturally identify interactions among correlates.

Random forests build multiple classification trees, using a random sample of subjects (bootstrap sample with replacement) and a random subset of predisposing variables eligible for consideration at each node of the tree. The accuracy of each tree is then determined by whether the tree correctly predicts the outcome for the subjects omitted from the development of the tree and provides validation. The proportion misclassified, averaged over all the trees, is an unbiased estimate of classification error. The relative predictive importance of each variable is determined by the difference in classification between the original tree and a tree in which the values for a single independent variable were intentionally jumbled (to remove its predictive power). A large difference in classification indicates the variable was an important predictor, while a small difference indicates the variable was not very important for classification. Variable importance, averaged over all of the trees, provides a relative ranking of correlates in their ability to classify subjects correctly with respect to suicidal ideation.

In a complex process like suicidal ideation, we chose to use classification trees to identify important interacting factors that would identify subgroups of persons at increased risk, rather than using regression-based methods to identify whether individual predictors were independently associated with suicidal ideation. Identification of subgroups at high risk emphasizes clinical applicability of the results, whereas identification of independent predictors is focused on etiology. To determine if any correlates in persons with arthritis were shared with persons with other chronic diseases, we ran random forests separately for persons with arthritis, diabetes mellitus, and cancer. In each group, results were based on forests of 500 trees each. Analyses were based on weighted samples to accommodate the survey design, and were done using R software (version 2.11.1) (21) and a fast parallelized implementation of the random forest algorithm called Random Jungle.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Descriptive data of the sample.

The mean ± SEM age of persons with arthritis was 61.5 ± 0.4 years (Table 1). Those with arthritis were more commonly women (60.4%), whites (78.9%), and had attended at least some college (26.7%). Suicidal ideation was present in prevalence ± SEM 5.6% ± 0.8% of people with arthritis. A similar prevalence ± SEM was found among those with diabetes mellitus (6.8% ± 1.4%) and cancer (5.1% ± 2.3%). The prevalence ± SEM among those without arthritis was 2.4% ± 0.4%. Sociodemographic characteristics, health behaviors, and comorbid conditions were generally similar among those with arthritis, diabetes mellitus, and cancer, with the exception of higher proportions of men in the diabetes mellitus and cancer groups (Table 1).

Table 1. Characteristics of persons ages 40 years or older with arthritis, diabetes mellitus, and cancer who participated in the National Health and Nutrition Examination Survey for 2007–2008*
 ArthritisDiabetes mellitusCancer within 2 years
  • *

    Values are the percentage unless otherwise indicated. PHQ-8 = Patient Health Questionnaire 8; ADL = activities of daily living.

Suicidal ideation5.66.85.1
Demographic and socioeconomic factors   
 Age, mean ± SEM years61.5 ± 0.462.3 ± 0.268.4 ± 1.0
 Male39.647.857.9
 Ethnicity   
  White78.964.186
  African American10.118.26.8
  Hispanic7.111.93.5
  Other3.95.83.7
 Born in the US91.78692.9
 Education level   
  Less than high school24.733.521.1
  High school graduate2827.925.5
  Some college26.72431.6
  College graduate20.614.621.8
 Marital status   
  Single5.161.9
  Married64.859.769
  Divorced/separated15.218.865
  Widowed14.915.522.6
 Social support   
  Emotional support93.289.195.1
  Financial support73.468.463.5
  No. of close friends, mean ± SEM7.2 ± 0.36.6 ± 1.38.2 ± 1.1
 Household income, median range dollars35,000–45,00035,000–45,00035,000–45,000
 Income:poverty ratio2.9:0.12.6:0.13.1:0.1
 Food security   
  Full83.781.292
  Marginal6.76.53.8
  Low5.67.31.8
  Very low452.4
 Insured91.889.896.3
 Presence of usual health care source96.397.896.8
 Mental health care visit in past year8.26.44.3
Health behaviors and comorbid conditions   
 Smoking status   
  Never44.547.543.8
  Former37.236.643.1
  Current18.315.913.1
  Cigarettes per day, mean ± SEM3.3 ± 0.63.1 ± 0.52.8 ± 1.0
 Alcohol status, mean ± SEM   
  Drinking days per month3.9 ± 0.61.9 ± 0.25.1 ± 0.8
  Binge days per month0.7 ± 0.10.4 ± 0.10.2 ± 0.08
 Illicit drug use   
  Current marijuana use2.81.70
  Current use of other illicit drugs0.20.30
 Heart disease15.627.521.1
 Stroke8.112.612.6
 Hypertension55.471.555.2
 Pulmonary disease25.326.621.6
 Liver disease5.53.75.5
 Arthritis10052.447.3
 Diabetes mellitus17.510018.5
 Cancer17.918.9100
 No. of comorbidities   
  02412.216
  1222430
  225.425.626.3
  311.922.418.8
  43.79.64
  51.75.52.7
  60.30.72.2
  7000
 PHQ-8 score, mean ± SEM4.1 ± 0.124.0 ± 0.13.1 ± 0.5
 Anxiety days in past month, mean ± SEM6.6 ± 0.55.7 ± 0.54.5 ± 0.7
 Sleep disturbances   
  Insomnia1.820.7
  Sleep duration <6 hours/night18.917.914.2
  Excessive daytime sleepiness   
   Never28.438.835.9
   Rarely19.414.317.4
   Sometimes29.62523.8
   Often14.511.716.6
   Almost always8.110.26.3
 Pain days past month, mean ± SEM7.8 ± 0.67.2 ± 0.96.8 ± 0.9
 Limitation in ADL   
  In/out of bed difficulty   
   None82.37982.4
   Some13.614.513.6
   Much3.55.63.2
   Unable0.60.90.8
  Dressing difficulty   
   None86.18490
   Some1110.67.9
   Much2.54.42.3
   Unable0.410.8
  Eating difficulty   
   None93.191.596
   Some6.26.53.1
   Much0.61.80.9
   Unable0.10.20
  Walking difficulty   
   None89.683.387.2
   Some7.411.58.3
   Much1.72.91.5
   Unable to do1.32.33
  Unable in at least 1 ADL243
  Special equipment use17.324.920

The characteristics of those with and without suicidal ideation among adults with arthritis are shown in Table 2. Persons with suicidal ideation were more likely nonwhite, had lower education levels, were poorer, and had a higher frequency of mental health care visits in the past year, current smoking, binge days per month, anxiety days, and pain days during the past month. They also had more comorbidities, sleep disturbances, depression, and ADL limitations.

Table 2. Characteristics of adults with and without suicidal ideation among those with arthritis*
 PresentAbsentP
  • *

    Values are the percentage unless otherwise indicated. PHQ-8 = Patient Health Questionnaire 8; ADL = activities of daily living.

Demographic and socioeconomic factors   
 Age, mean ± SEM years59.2 ± 2.061.4 ± 0.30.26
 Male37.740.10.72
 Ethnicity   
  White67.780.40.03
  African American11.49.8 
  Hispanic16.56.1 
  Other4.43.7 
 Born in the US86.693.40.005
 Education level   
  Less than high school42.523.00.0002
  High school graduate23.129.0 
  Some college27.226.6 
  College graduate7.221.4 
 Marital status   
  Single8.75.00.15
  Married53.365.3 
  Divorced/separated21.515.4 
  Widowed16.514.3 
 Social support   
  Emotional support82.793.9< 0.0001
  Financial support60.273.60.02
  No. of close friends, mean ± SEM5.5 ± 0.77.4 ± 0.30.02
 Annual household income, dollars   
  <20,00039.221.3< 0.0001
  20,000–44,99951.031.4 
  45,000–64,9994.914.6 
  ≥65,0004.932.7 
 Income to poverty ratio, mean ± SEM1.7 ± 0.23.0 ± 0.1< 0.0001
 Food security   
  Full58.184.8< 0.0001
  Marginal13.06.3 
  Low15.65.2 
  Very low13.33.7 
 Insured80.692.10.004
 Presence of usual health care source97.196.50.73
 Mental health care visit past year28.07.3< 0.0001
Health behaviors and comorbid conditions   
 Smoking status   
  Never32.044.2< 0.0001
  Former25.238.9 
  Current42.816.9 
  Cigarettes per day, mean ± SEM9.0 ± 1.43.0 ± 0.6< 0.0001
 Alcohol status, mean ± SEM   
  Drinking days per month2.1 ± 0.94.1 ± 0.60.003
  Binge days per month1.6 ± 0.80.6 ± 0.20.28
 Illicit drug use   
  Current marijuana use6.72.80.23
  Current use of other illicit drugs0.70.20.42
 Heart disease21.614.70.06
 Stroke17.97.30.001
 Hypertension74.554.70.04
 Pulmonary disease34.525.40.11
 Liver disease9.25.40.19
 Duration of arthritis, mean ± SEM years15.0 ± 1.613.6 ± 0.70.43
 Diabetes mellitus25.316.50.003
 Cancer18.517.60.84
 No. of comorbidities   
  00.825.5< 0.0001
  139.132.2 
  233.425.2 
  316.211.9 
  47.53.3 
  51.81.6 
  6 or 71.20.3 
 PHQ-8 score, mean ± SEM11.7 ± 0.83.7 ± 0.2< 0.0001
 Anxiety days in past month, mean ± SEM19.4 ± 1.25.9 ± 0.4< 0.0001
 Sleep disturbances   
  Insomnia7.41.40.001
  Sleep duration <6 hours/night36.217.90.006
  Excessive daytime sleepiness   
   Never9.028.1< 0.0001
   Rarely13.319.5 
   Sometimes26.931.2 
   Often27.114.1 
   Almost always23.77.1 
 Pain days in past month, mean ± SEM17.5 ± 1.37.2 ± 0.6< 0.0001
 Limitation in ADL   
  In/out of bed difficulty   
   None48.284.3< 0.0001
   Some32.612.8 
   Much17.82.3 
   Unable1.40.6 
  Dressing difficulty   
   None72.787.4< 0.0001
   Some18.010.4 
   Much6.92.0 
   Unable2.30.2 
  Eating difficulty   
   None76.494.2< 0.0001
   Some17.95.5 
   Much4.60.3 
   Unable1.10 
  Walking difficulty   
   None71.691.5< 0.0001
   Some18.76.2 
   Much7.71.2 
   Unable to do2.01.1 
  Unable in at least 1 ADL6.71.60.04
  Special equipment use37.614.9< 0.0001

Correlates for suicidal ideation.

Figure 1 shows the variable importance plots of correlates for suicidal ideation, based on the random forest. The most important correlates for suicidal ideation in individuals with arthritis were the following: depression evaluated by the PHQ-8, anxiety days per month, age, duration of arthritis, income:poverty ratio, number of close friends or relatives, pain, alcohol use, and excessive daytime sleepiness. Number of comorbidities was also important and ranked higher than any specific comorbid condition. Other important factors were marital status, education level, cigarettes per day, and difficulty in getting in or out of bed. Other measures, including country of birth, current use of marijuana or other illicit drugs, and the presence of a usual source of health care, were much less important in distinguishing those at high risk of suicidal ideation.

thumbnail image

Figure 1. Variable importance plots of correlates for suicidal ideation based on the random forest in adults with arthritis (A), diabetes mellitus (B), and cancer (C). PHQ8 = Patient Health Questionnaire 8; ADL = activities of daily living.

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The prevalence of suicidal ideation by the top 16 correlates is shown in Table 3. The prevalence of suicidal thoughts increased with PHQ-8 scores, number of days with anxiety, pain, excessive daytime sleepiness, more comorbid conditions, heavier smoking, binge drinking, and more difficulty transferring from the bed. Suicidal ideation was generally lower among those with a longer duration of arthritis, older age, higher income and income:poverty ratio, more close friends, more frequent light drinking, and more education.

Table 3. Prevalence of suicidal ideation by the top 16 correlates in persons with arthritis
CorrelatesSuicide ideation, %
Patient Health Questionnaire 8 score 
 <102.9
 10–1616.9
 17–2451.0
Anxiety days in past month 
 0–51.6
 6–147.6
 15–3019.1
Duration of arthritis, years 
 0–27.1
 2.1–5.04.1
 5.1–104.5
 ≥10.15.8
Age, years 
 40–547.5
 55–644.7
 ≥654.6
Income:poverty ratio 
 <0.59.7
 0.5–0.9912.5
 1.0–1.998.2
 ≥2.02.7
Pain days in past month 
 0–52.6
 6–146.1
 15–3013.7
No. of close friends 
 0–28.5
 3–65.8
 ≥73.4
Household income, median dollars 
 <45,0009.2
 45,000–75,0001.9
 >75,0001.1
Binge days per month 
 None4.6
 Any6.1
Excessive daytime sleepiness 
 Never1.8
 Rarely3.9
 Sometimes4.9
 Often10.2
 Almost always16.4
No. of comorbidities 
 00.2
 16.7
 27.3
 37.4
 411.9
 56.3
 614.5
 7100
Drinking days per month 
 0–56.3
 6–144.0
 15–302.1
Marital status 
 Single9.2
 Married4.6
 Divorced/separated7.6
 Widowed6.4
Education level 
 Less than high school9.8
 High school graduate4.5
 Some college5.7
 College graduate1.9
No. of cigarettes per day 
 03.9
 1–197.6
 ≥2018.7
In/out of bed difficulty 
 None3.2
 Some13.1
 Much31.0
 Unable12.9

To assess the commonality of the most important factors for suicidal ideation among persons with arthritis, diabetes mellitus, and cancer, we used the top 16 variables that were distinctly more predictive in the arthritis group. Eleven of the top 16 correlates in people with arthritis were also among the top correlates in people with diabetes mellitus and cancer, including the PHQ-8, anxiety, age, income:poverty ratio, social network, pain, binge drinking, and number of comorbidities. No correlates were unique to persons with arthritis.

The random forests were highly accurate. The cross-validated test set misclassification error for each of the random forests was 0, indicating that the set of correlates separated those with and without suicide ideation very well in each of the arthritis, diabetes mellitus, and cancer groups.

Subgroups of persons with arthritis at high risk for suicidal ideation.

A single classification tree analysis was performed using the top 16 correlates for suicidal ideation in adults with arthritis. This analysis demonstrates how individual correlates interact to identify particular subgroups of persons with arthritis at greatest risk for suicidal ideation. The tree fit the data well, with a 10-fold cross-validated test set misclassification rate of 3.56%. The risk for suicidal ideation varied most by PHQ-8 scores, duration of arthritis, binge drinking, income, and number of comorbidities (Figure 2). Among persons with arthritis, the subgroups most highly predisposed to suicidal ideation were those with PHQ-8 scores between 18 and 24 and less than 4.5 years of arthritis (96.5%), and those with PHQ-8 scores between 7 and 17, at least 1.24 days of binges per month, and either an annual income of $45,000 or higher (85.4%) or less than $45,000 and more than 3 comorbidities (70.8%). People with arthritis and PHQ-8 scores between 0 and 6 had a low predisposition to suicidal ideation (1.1%).

thumbnail image

Figure 2. Identification of subgroups at highest risk for suicidal ideation among adults with arthritis using classification tree analysis. PHQ-8 = Patient Health Questionnaire 8.

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DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

Suicidal ideation among adults with arthritis is of growing relevance to public health, given the increase in the projected prevalence of arthritis in US adults (23). Our study, using data from a nationally representative survey, showed that the prevalence of suicidal ideation in adults with arthritis was higher than that of persons without arthritis. Depression, anxiety, duration of arthritis, age, income:poverty ratio, social network, pain, alcohol use, excessive daytime sleepiness, and comorbidities were the most important correlates for suicidal thoughts among individuals with arthritis. Those with PHQ-8 scores between 18 and 24 and a short duration of arthritis (<4.5 years) were at highest risk for suicidal ideation.

Our findings were consistent with 2 previous studies showing that suicidal ideation was prevalent among adults with arthritis. One study examined 123 hospital outpatients with RA without including any control group, and the other used data from the Canadian Community Health Survey 2000–2001 (7, 8). A similar prevalence of suicidal thoughts among persons with arthritis, diabetes mellitus, and cancer was identified in our study, suggesting that the chronic nature of illness can impair the psychological well-being of people with these disorders (5, 6).

Despite continuing research, it remains difficult to predict which individuals are most vulnerable for suicidal behavior, which is never the consequence of a single cause (1). Mood disorders such as anxiety and particularly depression significantly increase the risk of suicidal thoughts in the general population and several medical conditions (24–26). Depression was also the main risk factor for suicidal ideation and suicide completion in studies of RA patients (7, 27). In our study, depression was the most important factor identifying subsets of individuals with arthritis affected with suicidal ideation. However, it is well established in the psychiatric literature that not only depression but also other mental illnesses (psychotic and personality disorders and alcohol/substance use), sociodemographic factors, and physical health problems contribute to suicidal ideation, each being interrelated (1, 28–30).

In our study, the risk for suicidal ideation was higher among adults ages 40–54 years compared to older people, those with a limited number of close friends or relatives, and those with a low income:poverty ratio (29, 31). Although suicide rates in elderly people have fallen in many countries, those in younger people have risen (1). Weak ties and low social support from friends or relatives have been significantly associated with suicidal thoughts in the literature (31, 32). Furthermore, data from psychiatric epidemiology surveys showed increased rates of suicidal ideation and suicidal attempts among adults with a low income and income:poverty ratio, which remained unchanged after adjusting for the presence of mental disorders (33, 34).

Regarding health behaviors and comorbidities, the results of our study were consistent with those of previous studies reporting that alcohol, smoking, and coexistence of arthritis with other chronic diseases were important correlates for suicidal thoughts (1, 35, 36). The screening for alcohol abuse is highly feasible in clinical practice and its detection should increase the suspicion for suicidal ideation in persons with depression. The presence of a general medical illness has been associated with an increased risk of both suicidal ideation and suicide attempts, and having more than one illness conferred a particularly high risk in the general population (37–39).

Persistent pain has been associated with elevated rates of suicidal behavior (40, 41). However, studies of chronic pain conditions have not adequately elucidated whether the increased risk of suicidal behavior is associated with pain per se or with the physical disability that pain produces (8, 42, 43). A recent review also suggested that sleep problems might be an indirect mechanism by which chronic pain is associated with suicidal thoughts (41). The present study indicates that mainly pain but also limitations in ADL and excessive daytime sleepiness were among the most important contributors for suicidal ideation in adults with arthritis, cancer, and diabetes mellitus. Excessive daytime sleepiness was a more important correlate than insomnia, possibly because it was much more prevalent than insomnia and therefore had a higher likelihood of demonstrating associations, but also because it may be a consequence of insomnia or a manifestation of depression.

Commonalities among the major correlates for suicidal ideation in individuals with arthritis, cancer, and diabetes mellitus include depression and anxiety, age, income:poverty ratio, social network, pain, binge drinking, and comorbidities. Eleven of the top 16 most important contributors for suicidal thoughts were common among arthritis and the other 2 chronic disease groups. This finding supports the general role of these factors in suicidal behavior among chronic diseases, regardless of the disease itself.

The results of the current study suggest that individuals with arthritis at high risk for suicidal thoughts should receive close monitoring and early intervention (44, 45). Self-report measures such as the PHQ-9 can be used as screening tools of depressive disturbances in outpatient clinics (44). Recognition and effective treatment of depression, anxiety, and comorbidities; enhancement of social support resources; and management of pain and physical disability are fundamentally important in reducing suicidal behavior (46–48). The strengths of this study include the large nationally representative sample and the wide range of sociodemographic, physical, and mental health factors examined. We also included pain and physical limitations, often present in persons with arthritis. We provided new information on the prevalence of suicidal ideation among individuals with arthritis, and on subgroups of people with arthritis most vulnerable for suicidal thoughts. The use of classification tree analysis helped to assess multiple correlates and their interactions to identify subgroups at greatest risk.

This study is limited in that the survey did not include some factors that may be associated with suicidal thoughts such as other psychiatric (e.g., personality disorders) or chronic pain diseases (abdominal pain, migraine). In addition, since the NHANES used a self-completed screening measure rather than an interview, we had to rely on the patient's interpretation of the question. However, the PHQ-9 is a screening instrument with high reliability and validity in the general population and various medical settings such as a primary care population, general hospital inpatients, and patients with rheumatic diseases (RA, osteoarthritis, fibromyalgia) (43, 49). Data on physician-diagnosed arthritis were also self-reported, but self-reports have been validated previously for surveillance purposes (10). Self-reported arthritis likely includes many types of arthritis that are represented in the study in proportion to their prevalence. An additional limitation is that our study cannot identify correlates of suicidal ideation that may be unique or specific to a given type of arthritis, and may not reflect correlates of suicidal ideation in less prevalent types of arthritis, such as RA. Data on medications and on prior suicide attempts were not available in the survey. Finally, the cross-sectional nature of the study precluded determination of causality.

In conclusion, suicidal ideation is prevalent among adults with arthritis and should be carefully evaluated by physicians. Depression and short duration of arthritis, binge drinking, income, and the presence of more than 3 comorbidities identified subgroups at greatest risk for suicidal ideation that should be the focus of prevention and intervention approaches.

AUTHOR CONTRIBUTIONS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES

All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be published. Dr. Tektonidou had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study conception and design. Tektonidou, Ward.

Acquisition of data. Tektonidou, Ward.

Analysis and interpretation of data. Tektonidou, Dasgupta, Ward.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. REFERENCES