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Published in final edited form as: J Acad Consult Liaison Psychiatry. 2021 Feb 12;62(4):413–420. doi: 10.1016/j.jaclp.2021.02.002

Limitations of Screening for Depression as a Proxy for Suicide Risk in Adult Medical Inpatients

Annabelle M Mournet a, Jarrod T Smith a, Jeffrey A Bridge b, Edwin D Boudreaux c, Deborah J Snyder a, Cynthia A Claassen d, David A Jobes e, Maryland Pao a, Lisa M Horowitz a
PMCID: PMC8258235  NIHMSID: NIHMS1673870  PMID: 34219655

Abstract

Introduction:

Medically ill hospitalized patients are at elevated risk for suicide. Hospitals that already screen for depression often utilize depression screening as a proxy for suicide risk screening. Extant research has indicated that screening for depression may not be sufficient to identify all patients at risk for suicide. The current study aims to determine the effectiveness of a depression screening tool, the Patient Health Questionnaire-9 (PHQ-9) in detecting suicide risk among adult medical inpatients.

Methods:

Participants were recruited from inpatient medical/surgical units in four hospitals as part of a larger validation study. Participants completed the PHQ-9 and two suicide risk measures: the Ask Suicide-Screening Questions (ASQ) and the Adult Suicidal Ideation Questionnaire (ASIQ).

Results:

The sample consisted of 727 adult medical inpatients (53.4% male; 61.8% White; mean age 50.1 ± 16.3 years). A total of 116 participants (16.0%; 116/727) screened positive for suicide risk and 175 (24.1%; 175/727) screened positive for depression. Of the patients who screened positive for suicide risk, 31.0% (36/116) screened negative for depression on the PHQ-9. Nearly 62.9% (73/116) of the individuals who were at risk for suicide did not endorse item 9 (thoughts of harming oneself or of being better off dead) on the PHQ-9.

Conclusion:

Using depression screening tools as a proxy for suicide risk may be insufficient to detect adult medical inpatients at risk for suicide. Asking directly about suicide risk and using validated tools is necessary to effectively and efficiently screen for suicide risk in this population.

Keywords: suicide, depression, screening, medical, inpatient, PHQ-9

Introduction

In 2020, the Centers for Disease Control and Prevention released a sobering update on suicide in the United States: not only has the suicide rate increased by 35% in the past two decades, but the rate of increase has accelerated since 2006.1 Regulatory organizations aiming to address this public health dilemma are increasingly recognizing medical settings as crucial venues for identifying suicide risk and deploying prevention strategies. The American Foundation for Suicide Prevention (AFSP), in partnership with Zero Suicide and the National Institute of Mental Health (NIMH), established Project 2025 which aims to reduce the suicide rate by 20% by 2025 with a focus on screening for suicide risk in healthcare systems.2

Given that medical patients are at elevated risk for suicide,3-5 The Joint Commission (TJC) issued Sentinel Event Alert 56 in 2016, recommending that all medical patients, including those in non-behavioral health settings, be screened for suicide risk using standardized, evidence-based tools.6 Sentinel Event Alert 56 highlighted the Patient Health Questionnaire (PHQ-9)7 depression screen as a potentially useful tool for identifying suicide risk in medical patients. While many hospitals utilize public domain depression screens such as the PHQ-9 as a proxy for suicide risk screening, the evidence supporting this practice is inconsistent.8-10

The association between suicide and depression is well-documented; however, extant research suggests that conditions other than depression correlate highly with suicide. Consequently, screening for depression may not adequately identify medical patients at risk for suicide. While 90% of suicide decedents meet criteria for mental illness, only 28% meet criteria for major depression.11 Furthermore, the contribution of major depression to suicide risk has been estimated at less than 50%12 and a significant correlation between medical illness and suicidality remains even after adjusting for depression.13 Numerous research studies have established the need to study and evaluate suicidality independent of mental health disorders.14,15 Thus, screening solely for depression in medical patients may not adequately detect suicidal ideation.16

In particular, the utility of item 9 of the PHQ-9 has been examined in medical populations.9,10 Item 9 asks how frequently a patient has been bothered by “thoughts that you would be better off dead, or of hurting yourself in some way” during the previous two weeks. Despite promising studies that have used this question to identify large numbers of at-risk patients,9,17 concerns have been raised regarding the sensitivity and specificity of item 9.18-20 Most troublesome is the mid-sentence “or,” which prevents one from knowing whether the respondent is endorsing the first or second half of the question. The phrase “hurting” is also used instead of “killing;” this ambiguous wording may both over and under detect patients at risk for suicide.9,10,21-23 The present study aims to address this divergence of evidence by identifying the extent to which depression screening is able to effectively detect adult medical inpatients who screen positive on suicide risk-specific measures.

Materials and Methods

Study Settings and Sample

Patients admitted to participating medical/surgical inpatient units at the National Institutes of Health Clinical Center (NIHCC), Rhode Island Hospital (RIH), Walter Reed National Medical Military Center (WRNMMC) and John Peter Smith Health Network (JPS) were recruited as part of a larger multisite instrument validation study24 approved by the Institutional Review Boards at all four sites. Exclusion criteria included age younger than 18, severe cognitive impairment, non-English speakers, previous enrollment in the study, and imminent discharge from the inpatient unit. No individuals were excluded from the study based on sex, race, or ethnicity.

After providing informed consent, participants completed a battery of self-report questionnaires, including two measures of suicide risk and a depression screen, administered by trained bachelor’s-level research assistants. Patients who screened positive for suicide risk or depression were managed as clinically indicated and received a brief suicide safety assessment (BSSA) by a clinical social worker, psychiatric nurse, or clinical psychologist. A full psychiatric consultation was administered if deemed clinically warranted. Additional resources were provided to patients as indicated.

Measures

The Ask Suicide-Screening Questions (ASQ)25 is a 4-item suicide risk screening tool that assesses recent and current suicide ideation, as well as lifetime suicide attempt (see Figure 1). A fifth item, prompted by endorsement of any of the initial four items, assesses imminent suicidality. A response of “no” to all four items is considered a negative screen. A “yes” response to any of the four initial items and a “no” response to the acuity item constitutes a non-acute positive screen. Responding “yes” to any of the first four questions and further endorsing the fifth acuity item denotes an acute positive screen and indicates imminent suicide risk. The larger validation study from which the data for this sub-analysis was derived established the ASQ to be a valid suicide risk screening tool among adult medical inpatients, with a sensitivity of 100%, a specificity of 89%, a negative predictive value of 100%, and a positive predictive value of 32%.24

Figure 1:

Figure 1:

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Ask Suicide-Screening Questions (www.nimh.nih.gov/ASQ)

The Adult Suicidal Ideation Questionnaire (ASIQ)26 is a 25-item gold standard instrument assessing severity of suicidal thoughts in the past month on a 7-point Likert scale (0=never had this thought; 6=had this thought nearly every day). The ASIQ has been psychometrically validated in adult psychiatric and normative populations,26,27 ranging in age from 18 to 88 years. The ASIQ demonstrates excellent internal consistency, with Cronbach’s alpha coefficient ranging from .96 to .98 in these samples.26,27 Over a one-week interval, the ASIQ showed high test-retest reliability (r = .95). The ASIQ was included as the gold standard in the larger adult instrument validation study and is included as an additional measure of suicide risk in the current sub-analysis. Participants with an ASIQ score of 31 or above revealed clinically significant suicidal ideation and are considered positive for suicide risk.

The Patient Health Questionnaire (PHQ-9)7 is a nine-item depression screening tool assessing depressive symptoms in the past two weeks on a four-point Likert scale (0=not at all; 1=several days; 2=more than half the days; 3=nearly every day). Item 9, the only suicide-related question in the instrument, asks how frequently a patient has been bothered by “thoughts that you would be better off dead, or of hurting yourself in some way.” Participants with a PHQ-9 score of 10 or above (indicative of moderate depressive symptoms) were considered positive screens for depression. Item 9 was considered “endorsed” if the participant provided a non-zero response.

Theory/calculation

Positive screens for suicide risk, positive screens for depression, and endorsement of item 9 were compared. For the purposes of the current study, suicide risk was defined as a positive screen on the ASQ and/or the ASIQ. These measures contain items that assess suicidal ideation and the ASQ adds an inquiry about lifetime suicide attempts. Suicidal ideation is typically defined as thoughts of engaging in suicide-related behavior.28,29 In addition to assessing thoughts of volitionally ending one’s life, the ASQ and the ASIQ also assess passive suicidal ideation, which is a desire to be dead (e.g. item 1 of the ASQ: “In the past few weeks have you wished you were dead?”). Past suicide attempts, or a potentially self-injurious behavior that is nonfatal and with some intent to kill oneself,28,29 is the most potent risk factor for future suicidal behavior.30 For this reason, the 4th item of the ASQ (“Have you ever tried to kill yourself?”) was forced into the ASQ during the development of the instrument.25

Univariate and multivariate statistics are reported to describe the association between depression and suicide risk screening. An odds ratio with a 95% confidence interval is reported to describe the relationship between suicide risk and depression screening outcomes. Additionally, a two-sample independent t-test was used to detect the difference between depression scores on the PHQ-9 among participants who were positive for risk of suicide compared to those who screened negative. Sensitivity and specificity were calculated to compare the performance of item 9 of the PHQ-9 in detecting suicide risk, relative to the gold standard ASIQ. SPSS Version 25 was used to conduct statistical analyses.

Results

A total of 740 individuals (74.4% enrollment rate) across the four study sites consented, enrolled, and completed the study measures; twelve participants withdrew from the study after data collection and one was excluded due to invalid responses, resulting in a total sample of 727 participants. The sample was predominantly male (53.4%; 388/727) and White (61.8%;449/727), with a mean age of 50.1 years (SD = 16.3, range = 18-93). Table 1 provides complete participant demographics.

Table 1.

Demographics of Study Participants (N = 727)

Gender
   Male 388 (53.4%)
   Female 337 (46.4%)
   Unknown 2 (0.2%)
Race or ethnicity
   White 449 (61.8%)
   African American 140 (19.3%)
   Hispanic/Latino 70 (9.5%)
   Asian 20 (2.8%)
   Multiple Races 20 (2.8%)
   Other 25 (3.4%)
   Unknown 3 (0.4%)
Mean Age (SD) 50.1 ± 16.3
Study Site
   NIHCC 198 (27.2%)
   RIH 178 (24.5%)
   WRNMMC 176 (24.2%)
   JPS 175 (24.1%)
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JPS = John Peter Smith Health Network; NIH CC = National Institutes of Health Clinical Center; RIH = Rhode Island Hospital; SD = standard deviation; WRNMMC = Walter Reed National Military Medical Center.

A total of 116 participants (16.0%; 116/727) screened positive for suicide risk on the ASQ and/or ASIQ. Specifically, 15.5% of participants (113/727) screened positive on the ASQ and 4.8% of participants (35/727) screened positive on the ASIQ. The average score on the ASIQ was 5.9 (SD = 13.6). A total of 175 (24.1%; 175/727) screened positive for depression. Forty-nine total participants (6.7%; 49/727) endorsed item 9 on the PHQ-9. A visual representation of the intersection between positive screens for depression and suicide risk appears in Figure 2.

Figure 2:

Figure 2:

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Relationship Between Positive Screens for Depression and Suicide Risk (N = 727)

Five percent of participants (5.0%; 36/727) screened positive for suicide risk only, and 13.1% of participants (95/727) screened positive for depression only. Ten percent of participants (10.2%; 74/727) screened positive for both depression and suicide risk, but only half of this group (5.1%; 37/727) also endorsed item 9 on the PHQ-9.

Of the 116 participants who were positive for suicide risk, nearly one-third of these participants (31.0%; 36/116) screened negative for depression on the PHQ-9 and did not endorse item 9. Additionally, when looking specifically at item 9, 62.9% (73/116) of the individuals who were at risk for suicide did not endorse item 9 on the PHQ-9.

Participants that screened positive for depression were nearly 9 times more likely to screen positive for risk of suicide compared to participants who screened negative for depression (OR: 8.9, 95% CI: 5.8-13.8, p <0.001). Participants who screened positive for suicide risk had a mean PHQ-9 score of 12.5 (SD = 7.1), while participants who screened negative for suicide risk had a mean PHQ-9 score of 5.0 (SD = 4.7). Participants who screened positive for suicide risk had significantly higher PHQ-9 scores than individuals who screened negative (t(725) = 14.4, p < .001, Cohen’s d = 1.25).

Classification statistics were also calculated to evaluate the ability of PHQ-9 item 9 and the ASQ to detect suicide risk, in comparison to the gold standard ASIQ. Compared to the ASIQ, item 9 had a sensitivity of 71% (95% CI = 54% to 85%) and a specificity of 97% (95% CI = 95% to 98%). In comparison, the ASQ had a sensitivity of 100% (95% CI = 90% to 100%) and a specificity of 89% (95% CI = 86% to 91%).24

Discussion

This comparative analysis of depression screening and suicide risk screening in adult medical inpatients revealed that nearly one-third of adult medical patients at risk for suicide would not have been detected if depression screening were used as the sole measure. Moreover, use of only item 9 on the PHQ-9 to detect suicide risk failed to identify over half (62.9%) of participants who were found to be at risk for suicide on the ASQ and/or ASIQ.

When compared to the gold standard ASIQ, item 9 on the PHQ-9 had strong specificity (96.5%) but less than optimal sensitivity (71.4%) for identifying suicide risk in this population. Conversely, the ASQ, a measure developed specifically for suicide risk, had very strong sensitivity (100%) and specificity (89%). Together, these findings support previous research16,18 suggesting that relying on item 9 to detect suicide risk may be inadequate and that asking directly about suicide may be a more effective way to screen.

Previous studies have established that the PHQ-9 is a highly effective depression screen.31 Moreover, among adult outpatients, Simon and colleagues found that item 9 of the PHQ-9 detected over 60% of patients that died by suicide.9 While this finding is encouraging that item 9 is able to identify suicide risk, it is important to note that 39% of suicide attempters and 36% of suicide decedents responded “not at all” to item 9.9 Further studies examining the utility of the PHQ-9, and specifically item 9, to screen for suicide risk in medical inpatients are warranted. Results from the current study demonstrate that by using a tool intended only to screen for depression, a portion of patients at risk for suicide may pass through medical hospitalization undetected. Clinicians who are seeking to detect patients at risk for suicide should utilize suicide-specific screening tools with sufficient sensitivity to ensure that at-risk patients are identified. It is important to remember that screening is only an initial step of a suicide prevention program. All positive screens should be followed up by evidence-informed suicide assessment tools. The ASQ BSSA32 or the Columbia-Suicide Severity Rating Scale (C-SSRS)33 are examples of second tier assessments that are supported by the Joint Commission for further assessing suicide risk.34 Hospitals seeking to implement suicide risk screening may also consider resources supported by Zero Suicide,35 the Safe Side approach,36 or the ASQ Toolkit.32

Screening often targets suicidal ideation, yet some studies show that a minority of individuals transition from suicidal ideation to suicidal behavior.37,38 Furthermore, according to research on the concept of suicide crisis syndrome, the transition to a suicidal crisis and engagement in suicidal behavior may happen rapidly, meaning that individuals experiencing a suicide crisis might not be screened for suicide risk in time to intervene.39 Despite these challenges, suicide risk screening can still be valuable as it allows for intervention with people who have suicidal thoughts, which most likely represents significant emotional distress.

This study has several limitations. First, data were collected from convenience samples of medical/surgical inpatients in hospitals located in urban or suburban settings, and it is unclear if these findings would generalize to other medical settings in more rural areas and to medical outpatients. Second, this study utilized a cross-sectional design; no longitudinal outcome data were collected. Lack of outcome data prevents true analysis of the predictive value of these instruments; however, these screening tools are meant to identify patients who may be struggling with suicidal thoughts and therefore warrant further mental health assessment, regardless of the likelihood of a future attempt. While comparison of these commonly used measures of depression, suicidal ideation, and suicidal behavior is important, complete overlap between screens for these distinct constructs would not be expected. Similarly, misalignment of time frames surveyed by these instruments may serve as a confound; the PHQ-9 assesses symptoms over the past two weeks, the ASQ surveys a variety of time frames, and the ASIQ asks about the past month.

Conclusion

In conclusion, depression screening is important, but may fail to adequately identify suicide risk in adult medical inpatients; unrecognized suicide risk can be a missed opportunity for suicide prevention. Asking directly about suicidal thoughts and past behaviors with a validated suicide risk screening instrument is a more sensitive and effective method for identifying at-risk medical patients who require further mental health assessment and if needed, intervention.

Acknowledgements:

The authors want to thank the following people who were instrumental to the success of the study, including Daniel Powell, Adam Rosenfeld, Jeanne Radcliffe, Eliza Lanzillo, Mary Tipton, Nathan Lowry, Keenan Withers, June Cai, Tram Dao, John Chaves, Samantha Chalker, Asher Siegelman, Janet Frazier, Louis French, Colin Harrington, Joan Salhany, Rumsha Hafeez, Amanda Hayes, Olla Elbasheer, Apoorva Deshpande, Mehreen Kahn, the Leadership of the Directorate of Behavioral Health of WRNMMC, and all the patients, nurses, mental health and medical teams that helped make the study run smoothly. The views expressed in this abstract are those of the author and do not reflect the official policy of the National Institute of Mental Health, National Institute of Health, Department of Health and Human Services or Department of Army/Navy/Air Force, Department of Defense, or U.S. Government.

Funding:

This research was supported in part by the Intramural Research Program of the NIMH (Annual Report Number ZIAMH002922).

Footnotes

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