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Signs of Mood and Anxiety Disorders in Chimpanzees
Open accessAbstract
BACKGROUND: In humans, traumatic experiences are sometimes followed by psychiatric disorders. In chimpanzees, studies have demonstrated an association between traumatic events and the emergence of behavioral disturbances resembling posttraumatic stress disorder (PTSD) and depression. We addressed the following central question: Do chimpanzees develop posttraumatic symptoms, in the form of abnormal behaviors, which cluster into syndromes similar to those described in human mood and anxiety disorders? METHODOLOGY/PRINCIPAL FINDINGS: In phase 1 of this study, we accessed case reports of chimpanzees who had been reportedly subjected to traumatic events, such as maternal separation, social isolation, experimentation, or similar experiences. We applied and tested DSM-IV criteria for PTSD and major depression to published case reports of 20 chimpanzees identified through PrimateLit. Additionally, using the DSM-IV criteria and ethograms as guides, we developed behaviorally anchored alternative criteria that were applied to the case reports. A small number of chimpanzees in the case studies met DSM-IV criteria for PTSD and depression. Measures of inter-rater reliability, including Fleiss' kappa and percentage agreement, were higher with use of the alternative criteria for PTSD and depression. In phase 2, the alternative criteria were applied to chimpanzees living in wild sites in Africa (n = 196) and chimpanzees living in sanctuaries with prior histories of experimentation, orphanage, illegal seizure, or violent human conflict (n = 168). In phase 2, 58% of chimpanzees living in sanctuaries met the set of alternative criteria for depression, compared with 3% of chimpanzees in the wild (p = 0.04), and 44% of chimpanzees in sanctuaries met the set of alternative criteria for PTSD, compared with 0.5% of chimpanzees in the wild (p = 0.04). CONCLUSIONS/SIGNIFICANCE: Chimpanzees display behavioral clusters similar to PTSD and depression in their key diagnostic criteria, underscoring the importance of ethical considerations regarding the use of chimpanzees in experimentation and other captive settings.
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Written from the paper’s full text.
TL;DR
This two-phase study applied DSM-IV and behaviorally anchored alternative criteria for PTSD and major depression to chimpanzees, finding symptom clusters similar to human mood and anxiety disorders. In phase 2, sanctuary chimpanzees with histories of trauma met alternative criteria for depression and PTSD far more often than wild chimpanzees.
Key findings
- In phase 1, among 20 published chimpanzee case reports, average diagnoses per rater were 3 of 20 for PTSD and 1 of 20 for major depression using DSM-IV criteria; using alternative criteria, averages were 3 of 20 for PTSD and 1.6 of 20 for major depression.
- Reliability was higher with alternative criteria: for PTSD, DSM-IV median percentage agreement was 43% and median Fleiss’ kappa was 0, versus 82% and 0.50 for alternative criteria; for depression, DSM-IV median agreement was 48% and median kappa was −0.10, versus 87% and 0.50 for alternative criteria.
- In phase 2, 58% of sanctuary chimpanzees (n = 168) met alternative criteria for depression versus 3% of wild chimpanzees (n = 196; p = 0.04), and 44% of sanctuary chimpanzees met alternative criteria for PTSD versus 0.5% of wild chimpanzees (p = 0.04).
- Where duration was reported, approximately 89% of individual alternative-criteria items for depression and PTSD persisted for at least 1 year; retest intra-rater percentage agreement averaged 81%–97%, with Cohen’s kappa averaging 0.40–0.80 across eight sites.
Methods
- Phase 1 searched PrimateLit for genus *Pan* using the term “nonadaptive,” screened results to 20 individually identifiable chimpanzee cases from 12 published papers, and had three raters apply DSM-IV PTSD and major depression criteria. The authors then developed behaviorally anchored alternative criteria using chimpanzee ethograms and consultation with primatology, ethology, psychology, and psychiatry experts.
- Phase 2 applied the alternative criteria at eight sites: three wild sites (n = 196) and five sanctuary sites (n = 168), including African sanctuaries and sanctuaries housing former laboratory chimpanzees. Three observers per chimpanzee completed surveys independently and were masked to study hypotheses; medical and behavioral records were also reviewed.
- Prevalence differences were tested with Mann-Whitney U tests using an alpha of 0.05 in SPSS version 18.0; test-retest reliability was assessed in a random subsample with questionnaires repeated after approximately 2 weeks.
Limitations
- Stated in the paper: chimpanzees cannot clearly articulate thoughts, feelings, and experiences; phase 1 relied on published case reports that may have contained biases or insufficient detail; some alternative-criteria items had low inter-rater reliability; there is no gold standard for assessing mood and anxiety disorders in chimpanzees, so external validity cannot be established; phase 2 was not longitudinal, did not allow full assessment of symptom duration or severity, was not designed for simultaneous observations, and relied on observer recall over differing time periods.
- Stated in the paper: comparability of wild and sanctuary data collection is a possible concern, though the authors argue wild chimpanzees are observed systematically and physiological reactions such as heavy or irregular breathing would likely be underestimated rather than overestimated.
- Evident from the text: the alternative criteria were developed and selected using the phase 1 case reports and expert consultation, then applied in phase 2, but the paper does not report independent validation against an external diagnostic standard; phase 2 prevalence estimates are based on caregiver/observer reports rather than direct clinical diagnosis.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The third hypothesis, that chimpanzees would display clusters of symptoms that are similar to disorders such as PTSD and depression, was supported.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Discussion
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In phase 2, there were differences between chimpanzees living in sanctuaries and those living in the wild in the percentages of abnormal behaviors (alternative criteria developed in phase 1) reported, as shown in Figures 1 and 2.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 2
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In the paper
“Where duration of behavior was reported, approximately 89% of the individual items for alternative criteria for depression (Figure 1) and PTSD (Figure 2) were reported to persist for at least 1 year.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 2
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“It was reassuring that there was 100 percent agreement (K = 1.0) among raters for the diagnosis of PTSD, when testing the set of alternative criteria in phase 1.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Discussion
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In the paper
“44% of chimpanzees in sanctuaries met the set of alternative criteria for PTSD, compared with 0.5% of chimpanzees in the wild (p = 0.04).”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Abstract > Methodology/Principal Findings
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In the paper
“When we tested the clusters of alternative criteria (i.e. the sets of criteria shown in Tables 2 and 3), there were significant differences between chimpanzees living in sanctuaries, compared with chimpanzees living in the wild.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 2
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Using the optimal set of alternative criteria for PTSD we identified, three raters agreed the same three chimpanzees met diagnostic criteria.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 1
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In the paper
“Raters reported that Eslom exhibited several ongoing behaviors consistent with the alternative criteria for PTSD.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Case Vignettes
Strength:plain· not yet calibratedSingle caseTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In both phase 1 and phase 2, multiple signs of abnormal chimpanzee behaviors similar to the criteria for PTSD and depression were reported.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Discussion
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In the paper
“The second hypothesis, that chimpanzees would manifest few, if any, criteria for PTSD or depression, was also not supported.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Discussion
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- It may state two separate claims as one. 19
- The quote only partly states this claim. 1
- Probably not a substantial claim. 15
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In contrast, percentage agreement among the three raters for each of the items in the alternative criteria for depression ranged from 63% to 100% (median = 87%) and inter-rater reliability Κ values ranged from 0.10 to 1.0 (median = 0.50).”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 1
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Although a number of chimpanzees met DSM-IV criteria for PTSD and depression in this phase, measures of inter-rater reliability were low.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Discussion
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“For major depression, one rater deemed three chimpanzees met DSM-IV criteria. However, the other two raters found no chimpanzees who met DSM-IV criteria for major depression.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 1
Strength:plain· not yet calibratedn = 4Tests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“For PTSD, using the DSM-IV criteria, one rater deemed that four chimpanzees met criteria; another rater deemed that two chimpanzees met criteria; and another rater deemed that three chimpanzees met criteria.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 1
Strength:plain· not yet calibratedn = 4Tests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Mawa met alternative criteria for depression and PTSD.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Case Vignettes
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The percentage agreement among the three raters for each of the 13 DSM-IV items for major depression ranged from 12% to 67% (median = 48%), and the inter-rater reliability Κ values for the three raters ranged from −0.40 to 0.40 (median Κ = −0.10).”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 1
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“For PTSD, percentage agreement among the three raters for each of the 21 items for the DSM-IV criteria ranged from 27% to 73% (median = 43%), while the inter-rater reliability Κ values for the three raters ranged from −0.30 to 0.30 (median = 0).”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 1
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In contrast, percentage agreement among the three raters for each of the items in the alternative criteria for PTSD ranged from 63% to 100% (median = 82%), and inter-rater reliability Κ values ranged from 0.10 to 0.70 (median = 0.50).”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 1
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Measures of inter-rater reliability, including Fleiss' kappa and percentage agreement, were higher with use of the alternative criteria for PTSD and depression.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Abstract > Methodology/Principal Findings
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesThe quote only partly states this claim.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Upon retest, percentage agreement within raters for individual symptoms averaged from 81% to 97%, with Cohen's kappa averaging from 0.40 to 0.80 at the eight sites.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 2
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The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Negra met alternative criteria for depression and PTSD.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Case Vignettes
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The search returned 384 results that met our initial criteria.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Methods > Methods overview
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Similarly, 44% of chimpanzees in sanctuaries met the definition for PTSD based on alternative criteria, compared with 0.5% of chimpanzees in the wild (p = 0.04).”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 2
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Using the optimal set of alternative criteria for depression we identified, one rater deemed that three chimpanzees met criteria; another rater deemed two chimpanzees met criteria; and another rater deemed that no chimpanzees met criteria.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Results > Phase 1
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Therefore, it is important to note that chimpanzees at the wild sites are typically observed for five days per week from dawn to dusk as part of systematic behavioral study.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Discussion
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In the paper
“Responses were made independently and without consultation.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Methods > Methods overview
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What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Inter-rater reliability was assessed by calculating Fleiss' kappa (Κ) and the percentage agreement for each item.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Methods > Methods overview
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In the paper
“The inability of nonhuman primates to report symptoms presents obstacles similar to those in pediatrics, psychiatry, and geriatrics, often requiring special investigative methods, including gathering information from relevant third parties [48]–[52].”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Introduction
What the sources say
- Not checked yetcites [48]–[52]
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What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“While respondents were informed that the study related to primate behavior, all were masked to the study hypotheses.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Methods > Methods overview
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Intra-rater percentage agreement was used to determine the reliability of the raters' assessments.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Methods > Methods overview
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What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Three raters who were aware of the purpose of the study rated all 20 cases independently.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Methods > Methods overview
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In the paper
“Likewise, other unfavorable rearing conditions, social isolation, prolonged captivity, sensory deprivation, and use in laboratory experimentation have been reported to be contributors to behavioral pathology in nonhuman primates [13]–[16].”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Introduction
What the sources say
- Not checked yetcites [13]–[16]
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
In the paper
“The association of pathological behaviors with captivity in nonhuman primates has been noted for decades [1]–[9].”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Introduction
What the sources say
- Not checked yetcites [1]–[9]
Strength:plain· not yet calibratedCausal:correlational· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Strengths of the current study include a robust sample size in phase 2 representing a wide age range of both sexes, as well as reports of trained observers, the broad spectrum of behaviors assessed, and the ability for caregivers to report observations in a relatively unrestricted but structured setting.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Discussion
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None of the sources cited for this claim have been checked yet.
In the paper
“Several authors have demonstrated the prevalence of abnormal behaviors, ranging from whole-body stereotypies to self-injurious behaviors, in chimpanzees and other nonhuman primates in captivity [6], [15], [17], [18].”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Introduction
What the sources say
- Not checked yetcites [6] LT Nash, 1999, Variables influencing the origins of diverse abnormal behaviors in a large sample of captive chimpanzees (Pan troglodytes)., Am J Primatol source
- Not checked yetcites [15] C Lutz, 2003, Stereotypic and self-injurious behavior in rhesus macaques: a survey and retrospective analysis of environment and early experience., Am J Primatol source
- Not checked yetcites [17] MA Hook, 2002, Inter-group variation in abnormal behavior in chimpanzees (Pan troglodytes) and rhesus macaques (Macaca mulatta)., Appl Anim Behav Sci source
Strength:boosted· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
None of the sources cited for this claim have been checked yet.
In the paper
“Abnormalities of this axis have been described in animals subjected to confinement, restraint, isolation, or surgical procedures [22], [23].”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Introduction
What the sources say
- Not checked yetcites [22] FD McMillan, 2005, Mental health and well-being in animals source
- Not checked yetcites [23] NG Gregory, 2004, Physiology and behavior of animal suffering
Strength:plain· not yet calibratedCausal:correlational· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“In phase 2, the design was not longitudinal and therefore did not allow for full assessment of the duration of symptoms and impeded the assessment of severity.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Discussion
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Complex PTSD, depression, and other psychiatric conditions have been diagnosed in other species, including chimpanzees [14], [22], [23], [41]–[46], although it is unclear how appropriate the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, 4th Ed.) criteria [47] or other traditional methods of assessing psychopathology are for use in species other than humans.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Introduction
What the sources say
- Not checked yetcites [14] GA Bradshaw, 2008, Building an inner sanctuary: complex PTSD in chimpanzees., J Trauma Dissociation source
- Not checked yetcites [22] FD McMillan, 2005, Mental health and well-being in animals source
- Not checked yetcites [23] NG Gregory, 2004, Physiology and behavior of animal suffering
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
In the paper
“Mood and anxiety disorders such as PTSD and depression are commonly diagnosed among humans exposed to significant acute, recurrent, or persistent trauma [72]–[76].”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Discussion
What the sources say
- Not checked yetcites [72]–[76]
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This is likely partly attributable to attempts to reduce the need to make inferences about thoughts or feelings.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Discussion
Strength:hedged· not yet calibratedCausal:conditional· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Cohen's kappa (K) was calculated to produce the most conservative estimate of intra-rater reliability.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Methods > Methods overview
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Test-retest was assessed in a random sub-sample of raters and chimpanzees at each site.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Methods > Methods overview
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✗ Load-bearing: fails✓ Based: passesProbably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“The study was not designed to capture simultaneous observations, therefore making it difficult to assess inter-rater reliability.”
§ Signs of Mood and Anxiety Disorders in Chimpanzees > Discussion
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
The paper relies on this without support.
It is uncommon to study psychopathology in nonhuman primates using the terms and tools of human psychiatry.
“Despite the many similarities between humans and nonhuman primates, it is uncommon to study psychopathology in nonhuman primates using the terms and tools of human psychiatry.”
The paper relies on this without support.
Pathological behaviors in nonhuman primates are often described in isolation without being distilled into recognizable syndromes.
“Moreover, pathological behaviors in these individuals are often described in isolation without being distilled into recognizable syndromes.”
The paper relies on this without support.
Diagnostic criteria for mood and anxiety disorders typically require verbal descriptions from subjects of their experiences and internal states.
“Diagnostic criteria for mood and anxiety disorders typically require verbal descriptions from subjects of their experiences and internal states.”
The paper relies on this without support.
Changes, disruption, or dysfunction of common neuropsychiatric systems can result in similar patterns of symptom expression.
“Similarly, changes, disruption, or dysfunction of common neuropsychiatric systems can result in similar patterns of symptom expression.”
The paper relies on this without support.
Chimpanzees cannot clearly articulate their thoughts, feelings, and experiences to humans.
“Chimpanzees cannot clearly articulate their thoughts, feelings, and experiences to humans, although a few have learned to communicate using sign language.”
The paper relies on this without support.
There is no gold standard for the assessment of mood and anxiety disorders in chimpanzees.
“Since there is no gold standard for the assessment of mood and anxiety disorders in chimpanzees, it is not possible to establish the external validity of the alternative criteria we developed.”
The paper relies on this without support.
The alternative criteria for PTSD and depression are valid indicators of these disorders in chimpanzees.
“We propose that these diagnostic terms be used, when applicable, in chimpanzees and offer criteria for their use.”
The paper relies on this without support.
Sanctuary chimpanzees are previously traumatized relative to wild chimpanzees.
“The significant differences we found in phase 2 between the wild and sanctuary populations in the percentage of chimpanzees who met a set of alternative diagnostic criteria for PTSD and depression suggest that syndromes similar to PTSD and depression are identifiable in previously traumatized chimpanzees.”
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
In the citing paper
“Captive apes, for example, have often experienced early trauma, lived in isolation or have suffered abuse. Those that have, often show disturbed behavior and social interactions compared to those who have not (Ferdowsian et al., 2011; Clay and de Waal, 2013).”
From Endogenous peripheral oxytocin measures can give insight into the dynamics of social relationships: a review (2014) · cites this paper as Ferdowsian et al., 2011
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Average alternative-criteria depression diagnoses is misrounded
MinorThe three raters diagnosed 0, 2, and 3 cases, for an average of 1.67 cases per rater. Rounded to one decimal place, this is 1.7, not the reported 1.6.
Reported 1.6 · recomputed 1.666667
“| | Average number of cases diagnosed per rater | 1 of 20 | 1.6 of 20 |”
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Metadata
- Authors
- Ferdowsian, H. R., Durham, D. L., Kimwele, C., Kranendonk, G., Otali, E., Akugizibwe, T., Mulcahy, J. B., Ajarova, L., & Johnson, C. M.
- Affiliations
- Physicians Committee for Responsible Medicine (US)
- University of Nairobi (KE)
- Kibale Chimpanzee Project (UG)
- Wildlife Conservation Society Uganda (UG)
- Corresponding author
- Ferdowsian, Hope R.
- Venue
- PLoS ONE
- Publisher
- Public Library of Science (PLoS)
- Published
- 2011-06-16
- Volume
- 6
- Issue
- 6
- Pages
- e19855
- ISSN
- 1932-6203 (ISSN-L)
- PMC
- PMC3116818
- OpenAlex
- W2098756499
- Semantic Scholar
- d9a5cc906e3214a5c0e35fe3448286e16061aa5a
- Cited by
- 124
- References
- 76
- Citations by year
- 2026: 4 · 2025: 8 · 2024: 7 · 2023: 7 · 2022: 9 · 2021: 7 · 2020: 20 · 2019: 6 · 2018: 4 · 2017: 4 · 2016: 6 · 2015: 13 · 2014: 11 · 2013: 4 · 2012: 13
- FWCI
- 12.62
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- cc-by
- Locations
- PLoS ONE (publishedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- WBI Studies Repository (submittedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- University of Nairobi Research Archive (University of Nairobi) (submittedVersion)
- Funders
- Arcus Foundation
- Ministrstvo za visoko šolstvo, znanost in tehnologijo
- Topics
- Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Primate Behavior and Ecology
- Life Sciences › Agricultural and Biological Sciences › Animal Science and Zoology › Animal Behavior and Welfare Studies
- Social Sciences › Psychology › Clinical Psychology › Posttraumatic Stress Disorder Research
- Keywords
- chimpanzees, post-traumatic stress disorder, depression, mood disorders, anxiety disorders, traumatic events, maternal separation, social isolation, animal experimentation, wild chimpanzees, diagnostic criteria, ethogram, inter-rater reliability, animal welfare ethics
- MeSH terms
- Animals, Anxiety, Pan troglodytes, Female, Male, Mood Disorders
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
A language model drew the claims from the paper on 2026-10-09, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).
A second model labelled each claim on 2026-10-09 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
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