Suicide Attempts Associated with Externalizing Psychopathology in an Epidemiological Sample

Article

Suicide Attempts Associated With Externalizing Psychopathology in an Epidemiological Sample

Edelyn Verona, Ph.D. Objective: Borrowing from recent di- factors were used in hierarchical logistic mensional models of psychopathology, regression analyses to predict history of Natalie Sachs-Ericsson, Ph.D. the authors conducted analyses that opti- suicide attempts associated with the pres- mized the common variance shared by ence of internalizing symptoms, external- Thomas E. Joiner, Jr., Ph.D. internalizing (depression, anxiety) and ex- izing symptoms, and comorbid internaliz- ternalizing (antisocial personality, sub- ing and externalizing symptoms. stance dependence) disorders in statistically predicting suicidal behaviors. These Results: After the investigators controlled relationships were analyzed in a large ep- for the presence of internalizing symptoms idemiological sample, thus allowing for and the comorbidity of internalizing and the examination of gender differences in externalizing symptoms, externalizing risk for suicide attempts associated with symptoms were related to suicidal behav- psychopathology. ior in both men and women, although comorbidity was most predictive of suicide Method: The data were obtained from attempts among women, compared to the Colorado Social Health Survey. Partici- men. pants (N=4,745) were a community sample recruited by household address. Struc- Conclusions: Suicidal behavior among tured clinical interviews were used to individuals with externalizing symptoms obtain lifetime diagnostic and symptom is not necessarily a result of comorbid de- count information. Symptom counts were pressive or other internalizing disorder. included in a factor analysis that yielded Thus, persons exhibiting antisocial behav- two main dimensions of psychopathology: iors should receive rigorous assessment internalizing and externalizing. These for suicidal ideation and behavior.

(Am J Psychiatry 2004; 161:444–451)

The growing incidence of suicidal acts among prison- They found that among violent male patients and adoles- ers (1) and jail detainees (2) has heightened awareness of cents with conduct disorder, sadness did not correlate the risk for suicide among persons characterized by crim- with suicidal behavior. On the other hand, the correlation inal, aggressive, and substance abuse behaviors. The im- between depression and suicidal acts was significant for portance of these “externalizing” syndromes, as well as of nonviolent hospital patients and adolescents with inter- “internalizing” forms of psychopathology such as depres- nalizing syndromes (7, 12). Although major depression is sive disorders, in predicting suicide is well established (3– an important precipitant, suicide risk among individuals 5). Most research examining suicide risk among individu- with externalizing disorders may instead be related to im- als who exhibit externalizing syndromes has been con- pulsive and anger-related behaviors. Despite this evi- ducted with forensic or psychiatric patients (6, 7). Al- dence, a few issues prevent firm conclusions about the though these subjects are often ideal for studies that roles of internalizing and externalizing psychopathology examine extreme behaviors, their inclusion impedes dis- in suicidal behavior. First, in the studies just discussed, the entangling the effects of incarceration or acute institu- tionalization from more stable underlying processes that study groups were composed of psychiatric patients, and place these persons at risk for suicide (8). Even in com- we wanted to examine whether these relationships could munity samples, the risk for suicide among persons ex- be found in the general population. Second, prior research hibiting acting-out behaviors may simply reflect risk asso- has not statistically controlled for depressive symptoms, ciated with the comorbidity of such behaviors with an or comorbidity between internalizing and externalizing internalizing axis I disorder, such as depression (9, 10). disorders, in analyzing the relationship between external- Mounting evidence supports the supposition that exter- izing disorders and suicidal behavior. Finally, few authors nalizing psychopathology represents a key risk factor for have examined gender differences in the effect of intern- suicide. In this regard, Apter and colleagues (7, 11) identi- alizing and externalizing disorders and their co-occur- fied at least two subtypes of individuals with suicidal be- rence on suicidal behaviors in a large group of men and haviors: depressed/withdrawn and irritable/aggressive. women from the community.

444 http://ajp.psychiatryonline.org Am J Psychiatry 161:3, March 2004 VERONA, SACHS-ERICSSON, AND JOINER

The high rate of comorbidity among mental disorders is composition of the sample was as follows: 2% (N=99) were Native relevant to the understanding of risk for suicide in differ- American, Asian, or Pacific Islander; 4% (N=178) were African ent diagnostic groups. Epidemiological data support the American; 84% (N=3,986) were Caucasian; and 10% (N=472) were Hispanic. high rate of comorbidity among depressive and anxiety disorders (13, 14), as well as the co-occurrence of external- Diagnostic Assessment izing symptoms (including antisocial and criminal behav- Participants’ psychiatric disorders were assessed by means of iors, excessive alcohol use, and aggressive acting out) the highly structured interview protocol of the National Institute within individuals (15–18). Krueger (19) suggested that of Mental Health Diagnostic Interview Schedule (DIS) (29). The DIS was used to obtain present and past DSM-III axis I diagnoses these patterns of comorbidity represent meaningful co- through a patterned series of specified questions. Questions per- variance. Specifically, he validated a two-factor model of taining to one axis II disorder, antisocial personality disorder, common mental disorders (i.e., not including schizophre- were also included in the interview. Robins and colleagues (29) nia and bipolar disorder): an internalizing factor repre- have demonstrated that the DIS has adequate reliability (kappa senting mood and anxiety disorders and an externalizing coefficients ranging from 0.60 to 0.86), and sensitivity and speci- ficity indices (true positive and true negative rates, respectively) factor that included antisocial personality disorder and al- that are in the adequate to excellent range (80%–94%). cohol and other substance dependence. This dimensional The following diagnoses were assessed: bipolar disorder model suggests that each factor (or cluster of related disor- (manic), major depression, dysthymic disorder, schizophrenia, ders) represents a common underlying process of psycho- obsessive-compulsive disorder (OCD), phobic disorder, panic pathology (20, 21). disorder, generalized anxiety disorder, alcohol abuse/dependence, other substance abuse/dependence, and antisocial per- Although some controversy exists in the interpretation sonality disorder. The criteria for receiving a diagnosis followed of Krueger’s analyses (22), his conceptualization provides directly from the criteria set forth in DSM-III. While there have a parsimonious approach to examining the influence of a been some modifications in diagnostic criteria from DSM-III to collection of correlated syndromes on outcomes. Follow- DSM-IV, for the most part changes have been minimal and there ing this framework, we attempted to validate this two-fac- is considerable overlap. The fact that we conducted primary analyses by using symptom count variables (see later discussion) and tor structure of mental disorders in an epidemiological not diagnoses largely resolves concerns about discrepancies in sample and extended Krueger’s work by including both criteria across different versions of DSM. For the purposes of this schizophrenia and bipolar disorder in these analyses to study, lifetime diagnostic and symptom information were used as determine if these inclusions would change the factor independent variables. Our hypothesis was that the vulnerability structure. Then, factor scores were used in regression to externalizing disorders (evidenced by the participant’s having experienced a series of externalizing symptoms at some point in analyses to determine whether externalizing psycho- his or her lifetime), and not just the current presence of the syn- pathology predicts risk for suicide attempts above the drome, represents the underlying risk for suicidal acts. variance accounted for by the presence of internalizing The lifetime prevalence of generalized anxiety disorder (17%) symptoms and comorbid internalizing and externalizing in the Colorado Social Health Survey was higher than that re- symptoms. ported in other samples (30), but the discrepancy was due mostly to the difference in duration criteria from DSM-III (1 month) to In addition, we were interested in whether these effects DSM-III-R and DSM-IV (6 months). A reanalysis of the data for would be similar for both genders. Typically, women are this diagnosis by using more stringent duration criteria (i.e., more likely to experience depressive and internalizing symptoms that lingered or recurred for longer than 1 month) re- symptoms and engage in suicide attempts (23–25), but ex- sulted in a lifetime prevalence (6.3%) similar to that found in ternalizing behaviors are more strongly associated with other epidemiological studies (30). In addition, to avoid con- founding diagnostic (major depression) and outcome (suicide) men (26). Thus, we explored whether the effect of exter- variables, major depression diagnoses and symptom counts were nalizing disorders on suicide was equally robust for both calculated with the omission of data from the survey questions genders. about suicidal ideation or suicide attempts. This change affected 62 persons who would have met the criteria for a lifetime diagnosis of major depression but subsequently, with this revision, did Method not. It is interesting to note that the prevalence of suicide attempts among persons with a lifetime major depression diagno- Participants sis was very similar when we used the original criteria (24.6%) and The data for this study were obtained as part of the Colorado when we used the revised criteria (24.3%). Dysthymic disorder, al- Social Health Survey (27), which included an epidemiological cohol abuse, and other substance abuse were not included in the sample of the Colorado general adult population (N=4,745). The analyses because of symptom overlap with their more severe ver- survey method was patterned after that of the Epidemiological sions (major depression, alcohol dependence, and other sub- Catchment Area program (see reference 28). During 1985–1986, stance dependence). A diagnosis of childhood conduct disorder participants were randomly sampled by household address, and was not used in the analyses of the dichotomous diagnostic vari- potential respondents were then interviewed in their homes by ables because only adult diagnoses were included. However, a trained lay interviewers. Participants were first provided with a symptom count for childhood antisocial behavior was calculated description of the study, and they signed an informed consent for use in the factor analysis. form. Ciarlo and colleagues (27) have provided a full description Symptom Count Variables of the Colorado Social Health Survey procedures. The mean age of the participants was 43.0 years (SD=17.5); 48% (N=2,265) of the For the factor analysis and logistic regression analyses, we used sample were men, and 52% (N=2,479) were women. The ethnic symptom count variables (number of symptoms endorsed for

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TABLE 1. Lifetime Prevalence of 10 DSM-III Disorders and Suicide Attempts in a Community Sample of Adults (N=4,745)a Subjects With Diagnosis Subjects With Diagnosis Who Attempted Suicideb Analysis Disorder N % N % Odds Ratio χ2 (df=1) Internalizing disorders Major depressionc 221 4.7 54 24.3 7.14 281.26* Generalized anxiety disorder 812 17.1 91 11.2 4.81 157.66* Phobic disorder 584 12.3 56 9.6 3.17 66.92* Obsessive-compulsive disorder 80 1.7 13 16.3 4.11 36.80* Panic disorder 88 1.9 13 14.7 3.79 31.60* Externalizing disorders Alcohol dependence 752 15.8 67 8.9 3.11 69.53* Other substance dependence 248 5.3 35 14.6 4.23 92.79* Antisocial personality disorder 261 5.5 27 10.3 2.93 32.27* Less common disorders Schizophrenia 32 0.7 15 46.9 7.80 171.38* Bipolar disorder (manic) 9 0.2 5 55.6 7.19 68.74* a Data from the Colorado Social Health Survey (27), a statewide survey of the Colorado general adult population conducted during 1985–1986. b The number and percentage of persons within each diagnostic category who reported a history of suicide attempts. c Prevalence of major depression was determined by excluding criteria related to suicidal ideation and suicide attempts. *p<0.01. each disorder), instead of the dichotomous diagnosis variables time symptoms) previously described. Hierarchical logistic regres- (present versus absent) (20, 21). Psychopathology researchers sion analyses were then performed, wherein dichotomous lifetime have argued that symptoms of mental disorders are distributed suicide attempt history was the criterion variable. Gender, the in- continuously in the population, with increasing symptom levels ternalizing and externalizing factors that resulted from the factor indicative of greater dysfunction (31). In addition, symptom analysis, and their interactions were included as independent count variables yield greater statistical power in studies of general variables in these regression analyses. A significant reduction in population samples with lower base rates of psychopathology, the (–2)log likelihood estimate from the restricted model (with the compared with clinical samples (21). Moreover, Krueger (32) has internalizing factor and gender as predictors) to the full model confirmed that analyses of symptom counts result in distinct life- (which included the externalizing factor in a second step, the in- time patterns of comorbidity that are not solely attributable to ternalizing factor-by-externalizing factor interaction term in a criterion overlap. third step, and the internalizing factor-by-externalizing factor-by- For each disorder, the symptom count variables corresponded gender interaction in a final step) would represent an improve- to the following DSM-III criteria: for major depression, criteria A ment in statistical prediction of suicide history, which was calcu- and B; for alcohol and other substance dependence, criteria A, B lated as a chi-square statistic with a corresponding p value (36). and C; for panic disorder, criteria A and B; for generalized anxiety disorder, criteria A and B; for phobic disorder, all symptom crite- Results ria; for OCD, criterion A; for schizophrenia, criteria A, B, and C; and for bipolar disorder (manic), criteria A and B. Antisocial per- History of Suicide Attempts Across sonality disorder symptoms were divided into adult antisocial behavior and child antisocial behavior symptoms (i.e., DSM-III cri- Diagnostic Groups terion C for antisocial personality disorder). The symptom count Across the overall sample, 173 persons (3.7% of the sam- variables were positively skewed in distribution; thus, we used a ple) reported that they had attempted suicide in their life- rank-normalizing transformation previously used in these types of analyses (33). time. Women were significantly more likely to report suicide attempts (N=128; 5.2% of women) than men (N=44; History of Suicidal Behavior 1.9% of men) (χ2=35.14, df=1, N=4,744, p<0.001). Infor- As part of the assessment procedure, participants were asked mation on gender was not available for one person who about history of suicidal behavior. For purposes of this study, we reported a suicide attempt. As reported in Table 1, all chose to focus on suicide attempts, because a suicide attempt lifetime diagnostic conditions (present versus absent, represents a more severe manifestation of suicidal behavior than does suicidal ideation. Although some data suggest that suicide without regard to comorbidity) were significantly related attempters differ from persons who die by suicide (34), research to a history of suicide attempts. Since the large sample size indicates that self-harm not resulting in death is related to a high may have influenced the p value estimates, we also calcu- risk for eventual suicide (6, 35). A dichotomous variable repre- lated odds ratios and reported them in Table 1. It is typical senting lifetime history of suicide attempts was used as the de- to report odds ratios in such cases to best evaluate the pendent variable to ensure that we obtained a large enough group of suicide attempters for the analyses. contribution of each diagnostic syndrome in the prediction of suicide attempts (9). An examination of Table 1 re- Statistical Analyses veals that, of the internalizing disorders, major depression First, chi-square analyses were conducted to determine confers the most risk for suicidal acts (37). The other in- whether lifetime diagnoses (present or absent) statistically pre- ternalizing disorders (anxiety disorders) and the external- dicted suicide attempt history. Then, we employed the common izing disorders (antisocial personality disorder, alcohol extraction method of principal axis factor analysis (20) to examine the relationships between the common mental disorders (i.e., dependence, and other substance dependence) were sim- the 11 transformed symptom count variables representing life- ilarly predictive of suicide attempts.

446 http://ajp.psychiatryonline.org Am J Psychiatry 161:3, March 2004 VERONA, SACHS-ERICSSON, AND JOINER

TABLE 2. Lifetime Prevalence of Suicide Attempts in a Community Sample of Adults in Four Diagnostic Categories, by Gendera Diagnostic Category and Analysis Overall Sample (N=4,745)b Men (N=2,265) Women (N=2,479) Attempted Suicide Attempted Suicide Attempted Suicide Diagnostic category Total N N % Total N N % Total N N %

No lifetime history of any DSM-III disorder 2,842 28 1.0 1,305 4 0.3 1,536 24 1.6 At least one internalizing disorderc 893 54 6.0 239 7 2.9 653 47 7.2 At least one externalizing disorderd 607 17 2.8 487 7 1.4 119 9 7.6 Both internalizing and externalizing disorders 404 75 18.6 233 26 11.2 171 49 28.7

Analysise χ2 p χ2 p χ2 p

All diagnostic groups (df=3) 327.35 <0.001 124.05 <0.001 238.53 <0.001 At least one internalizing disorder versus at least one externalizing disorder (df=1) 8.45 <0.01 1.89 n.s. 0.02 n.s. At least one internalizing disorder versus both internalizing and externalizing disorders (df=1) 48.66 <0.001 12.29 <0.001 60.62 <0.001 At least one externalizing disorder versus both internalizing and externalizing disorders (df=1) 72.87 <0.001 34.06 <0.001 19.51 <0.001 a Data from the Colorado Social Health Survey (27), a statewide survey of the Colorado general adult population conducted during 1985–1986. b One person with a suicide attempt did not indicate gender. c Major depression and/or any of the anxiety disorders. d Antisocial personality disorder, alcohol dependence, and/or other substance dependence. e Test of significance of differences in prevalence of suicide attempts between the different diagnostic categories.

As has been found in other work, schizophrenia and bi- attempt suicide than those with only an internalizing di- polar disorder (manic) were strongly associated with sui- agnosis or only an externalizing diagnosis (Table 2). cidal behaviors, with risk just slightly higher than that for major depression. Consistent with other epidemiological Latent Structure of Mental Disorders investigations, the base rates of schizophrenia (N=32) and Borrowing from the literature on dimensional models of bipolar disorder (manic) (N=9) were low (below 1%) in this psychopathology (19, 38), we conducted a principal axis sample, making conclusive statements about these rela- factor analysis, with promax rotation, using the 11 symp- tionships quite tenuous. In addition, all of the persons tom count variables described earlier. The scree plot and meeting the criteria for schizophrenia or bipolar disorder eigenvalues (>1) revealed a clear two-factor solution; fac- (manic), except one, met the criteria for another disorder. tors other than the two major factors had trivial eigenval- For both of these diagnoses, comorbidity was mostly with ues (Table 3 provides eigenvalues and factor loadings for an internalizing disorder or with comorbid internalizing the full sample and for each gender). The major depres- and externalizing disorders. Only four participants with a sion, panic disorder, generalized anxiety disorder, and schizophrenia diagnosis had only an externalizing comor- phobia symptom count variables loaded highly on the first bid disorder. factor (the internalizing factor), and OCD loaded moder- Among participants with a “pure” externalizing or inter- ately on this factor. The internalizing factor variables nalizing disorder, women were more likely than men to loaded negligibly on the second factor. Symptom counts have a history of an internalizing disorder (χ2=193.27, df= for adulthood antisocial behavior, childhood antisocial 1, N=4,744, p<0.001). Men were more likely than women to behavior, alcohol dependence, and other substance de- have a history of an externalizing disorder (χ2=294.43, df= pendence loaded highly on the second factor (the exter- 1, N=4,744, p<0.001) and of both internalizing and externalizing factor) and negligibly on the first factor. Separate nalizing disorders (χ2=17.91, df=1, N=4,744, p<0.001). In analyses performed on the symptom count data for men Table 2, we present the prevalence of suicide attempts by and women revealed very similar two-factor solutions, in- diagnostic categories. Chi-square analyses revealed that dicative of internalizing and externalizing factors, for both participants in each of the psychopathology groups were genders (Table 3). more likely to have attempted suicide than participants Schizophrenia and bipolar disorder symptoms loaded with no prior psychopathology (Table 2). Those with only highly on the internalizing factor and negligibly on the ex- an internalizing diagnosis were slightly more likely to have ternalizing factor (Table 3); this pattern may have oc- attempted suicide than participants with only an external- curred because persons with these symptoms were more izing diagnosis, although this result was not significant likely to also have internalizing symptoms, as was dis- when analyses were conducted separately for men and cussed earlier. The result may also be an artifact of the low women. Participants who met the criteria for both inter- base rates of schizophrenia and bipolar disorder (manic) nalizing and externalizing diagnoses were more likely to symptoms; thus, a separate factor could not be detected in

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TABLE 3. Eigenvalues and Factor Loadings for Promax-Rotated Internalizing and Externalizing Dimensions Extracted From Principal Axis Factor Analysis of Psychiatric Symptom Counts in a Community Sample of Adults, by Gendera Overall Sample (N=4,745)b Women (N=2,479) Men (N=2,265) Internalizing Externalizing Internalizing Externalizing Internalizing Externalizing Variable Factor Factor Factor Factor Factor Factor

Eigenvalue 2.3 2.3 2.4 2.2 2.4 2.4 % Variance 30.4 15.4 31.3 13.1 13.8 31.6 Factor loadings Major depression 0.71c 0.02 0.69c 0.03 0.65c 0.07 Generalized anxiety disorder 0.56c –0.07 0.60c –0.10 0.48c –0.04 Phobic disorder 0.47c –0.04 0.44c –0.06 0.54c –0.11 Obsessive-compulsive disorder 0.40c 0.15 0.46c 0.09 0.37c 0.14 Panic disorder 0.49c 0.02 0.45c 0.02 0.50c 0.01 Alcohol dependence –0.03 0.66c 0.05 0.54c 0.01 0.74 Other substance dependence 0.01 0.61c –0.11 0.72c –0.04 0.62 Childhood antisocial behavior –0.07 0.71c –0.03 0.65c –0.06 0.69 Adulthood antisocial behavior 0.06 0.71c 0.11 0.62c –0.01 0.74 Schizophrenia 0.47c 0.03 0.43c 0.08 0.50c –0.04 Bipolar disorder (manic) 0.49c 0.15 0.53c 0.08 0.52c 0.10 a Data from the Colorado Social Health Survey (27), a statewide survey of the Colorado general adult population conducted during 1985–1986. b One person did not indicate gender. c Factor loading >0.30. the analyses. We excluded the schizophrenia and bipolar factor, and externalizing factor), we also conducted hierar- disorder symptom counts from the calculation of the two chical regression analyses separately by gender (indepen- internalizing and externalizing factor scores because their dent variables included the internalizing factor, external- inclusion may have confounded the interpretation of the izing factor, and internalizing factor-by-externalizing two factors (since schizophrenia and bipolar disorder factor) (Table 4). For women, the internalizing factor was [manic] symptoms loaded on the internalizing factor and a significant predictor in the first step and improved not on the externalizing factor). With this exclusion, scores model fit above a constant, as did the externalizing factor on the internalizing and externalizing factors, extracted in the second step of the model. In addition, the interac- from the overall analyses, were used as independent vari- tion between internalizing and externalizing factors was a ables in the regression analyses predicting suicide attempt significant predictor of suicide attempts in the final step; history. the interaction improved model fit further for women. For men, the internalizing factor in the first step and the ex- Risk for Suicide Associated With Internalizing ternalizing factor in a second step both made indepen- and Externalizing Factors dent significant contributions to prediction; however, for We conducted a hierarchical logistic regression analysis men, the internalizing factor-by-externalizing factor in- with four steps (Table 4 provides [–2]log likelihood, chi- teraction term included in the third step of the analyses square, and Wald statistics for all steps of the analysis). did not improve model fit significantly. These results sug- Gender and internalizing factor scores were included as gest that when internalizing and externalizing factor ef- predictors in the first step, which significantly improved fects are held constant, their co-occurrence plays a more prediction of suicide attempts above a constant. When ex- influential role in suicidal behaviors among women than ternalizing factor scores were entered in a second block, among men. the model fit was significantly improved. Then, the internalizing factor-by-externalizing factor interaction term Discussion was included in a third step, which also improved model fit. It is important to note that the contribution of the ex- An innovative aspect of this study was the application of ternalizing factor remained highly significant in this third dimensional models of psychopathology (19, 38) to the ex- step (Wald χ2=53.21, df=1, p<0.001). Finally, the internaliz- amination of relations between internalizing or external- ing factor-by-externalizing factor-by-gender interaction izing symptoms and suicidal behavior. Although a large included in a final step was not significant in predicting literature has confirmed relationships between suicidal suicide attempts (p=0.09) (Table 4). Also, in this step, the behaviors and externalizing syndromes (5, 39–41), a two-way internalizing factor-by-externalizing factor inter- number of these studies have been conducted with incar- action became nonsignificant in this final step (p=0.74), cerated or psychiatric subjects. Our results support the va- whereas the externalizing factor main effect remained lidity of the link between externalizing syndromes and sui- highly significant (Wald χ2=54.80, df=1, p<0.001). cidal behavior in a large community sample, confirming Due to the significant gender differences on all the vari- that this relationship is robust across psychopathological ables of interest (history of suicide attempts, internalizing and “normal” populations.

448 http://ajp.psychiatryonline.org Am J Psychiatry 161:3, March 2004 VERONA, SACHS-ERICSSON, AND JOINER

In addition, our data provide support for the thesis that TABLE 4. Hierarchical Logistic Regression Analysis Predict- the relationship between a history of suicidal behavior and ing History of Suicide Attempts in a Community Sample of Adults and Among Men and Women in the Samplea a history of impulsive, deviant (externalizing) behaviors is Step independent of internalizing symptoms and independent c (–2)Log Analysis Wald χ2 of comorbidity between internalizing and externalizing Sample and Factor Likelihoodb χ2 df (df=1)d symptoms. Indeed, the results of the chi-square analyses of Overall sample (N=4,745)e diagnostic categories showed that persons who had inter- Gender 1144.94f 337.08† 2 13.42† f nalizing disorders did not differ in rate of suicide attempts Internalizing factor 1144.94 337.08† 2276.45† Externalizing factor 1089.46 55.49† 1 55.44† from those with externalizing disorders. A more important Internalizing factor- finding was that the results of the regression analyses of by-externalizing factor 1084.78 4.68** 1 4.96** symptom count data suggested that the common variance Internalizing factor-by- externalizing factor- associated with these disorders (i.e., the externalizing by-gender 1081.82 2.96* 1 2.90* factor dimension) is predictive of a history of suicide at- Men (N=2,265) tempts. As suggested by Krueger and colleagues (19, 21), a Internalizing factor 322.86 113.42† 1103.57† Externalizing factor 311.59 11.27† 1 11.14† common vulnerability factor may underlie the co-occur- Internalizing factor- rence of externalizing behaviors; our data indicate that sui- by-externalizing factor 310.01 1.58 1 1.70 cide risk among persons with externalizing syndromes Women (N=2,479) Internalizing factor 819.38 189.71† 1174.14† may also be related to this common diathesis (5). The un- Externalizing factor 775.74 43.65† 1 43.87† derlying mechanism in this relationship (e.g., impulsivity) Internalizing factor- would theoretically be different from the mechanism that by-externalizing factor 767.90 7.83*** 1 8.13*** a links suicide to depressive and other internalizing disor- Data from the Colorado Social Health Survey (27), a statewide survey of the Colorado general adult population conducted during ders (e.g., hopelessness) (7, 11, 12). 1985–1986. Results from the current study point to other areas for b Significant decreases from the previous model represent improve- ment in prediction when including the next predictor. future study. Research on normal personality links to psy- c Estimate of the increment in prediction provided by the particular chopathology can help in identifying the common risk step of the model (inclusion of new variable to the model). factor for externalizing and suicidal behaviors. For exam- d Test of the variable’s independent contribution to the prediction of suicide attempts, after other predictors are held constant. ple, in a study by Verona et al. (42), analyses revealed that e One person with a suicide attempt did not indicate gender. extremes in personality traits reflective of negative emo- f Gender and the internalizing factor were included together in the tionality and (low) constraint accounted for the relation- first step of the model; thus, (–2)log likelihood and chi-square statistics for that step are the same for gender and for internalizing ship between antisocial behavior history and suicide at- factor. tempt history among male offenders. Moreover, Krueger *p<0.10. **p<0.05. ***p<0.01. †p<0.001. and colleagues (20, 21) have confirmed that the externalizing spectrum of disorders is related to the genetically to the combination of emotional instability (such as de- linked personality trait of low constraint. Although trait pression or anxiety) and behavioral disconstraint (repre- negative emotionality may represent vulnerability to both sented by acting-out behaviors) (43). This latter descrip- internalizing and externalizing psychopathology (and tion is reminiscent of borderline personality traits, which thus explain their comorbidity), low constraint seems to are strongly linked to self-harm in women. Unfortunately, be related to engagement in externalizing versus internal- the Colorado Social Health Survey did not obtain informa- izing behaviors (20). Application of this hypothesis to the tion on borderline personality disorder, which is a limita- relationship between suicidal behavior and externalizing tion of this study. Thus, we could not investigate this hy- symptoms should be examined directly in future work. pothesis directly, although such an endeavor would be an Another important contribution of this study is the important contribution in future work. analysis of relationships between psychopathology and Some have suggested that substance dependence and suicidal behavior in men and women separately. As in earlier studies, women were more likely to engage in suicidal antisocial personality disorder in men may be the equiva- behaviors than men, probably because they had a higher lents of depression or anxiety in women and, thus, that ex- prevalence of depression, which was a strong predictor of ternalizing syndromes may represent unrecognized de- suicide attempts. However, externalizing psychopathol- pression in men (see reference 44). However, in our study, ogy uniquely predicted suicidal behaviors in both gen- men were more likely than women to endorse both inter- ders, even though women showed fewer externalizing nalizing and externalizing symptoms; thus, the differential symptoms. On the other hand, women, more than men, results for men and women are too preliminary to interpret showed strong relationships between comorbid external- fully. Nonetheless, these results suggest that gender differ- izing and internalizing psychopathology and suicide at- ences in the link between psychopathology and suicide tempt history. These results are only preliminary and should be explored further in other samples in which rates require replication; however, they suggest that suicidal be- of suicide attempt are higher, especially among male par- haviors in women with externalizing symptoms may relate ticipants (see reference 45).

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