Research report Impulsivity: Differential relationship to depression and mania in bipolar disorder☆

Alan C. Swann⁎, Joel L. Steinberg, Marijn Lijffijt, F. Gerard Moeller
Department of Psychiatry and Behavioral Sciences University of Texas Health Science Center Houston, Texas, USA
Received 25 January 2007; received in revised form 12 June 2007; accepted 11 July 2007 Available online 5 September 2007
Abstract
Introduction: Impulsivity, a component of the initiation of action, may have a central role in the clinical biology of affective disorders. Impulsivity appears clearly
to be related to mania. Despite its relationship to suicidal behavior, relationships between impulsivity and depression have been studied less than those with mania.
Impulsivity is a complex construct, and it may be related differently to depression and to mania. Methods: In subjects with bipolar disorder, we investigated
impulsivity in relationship to affective symptoms. Trait-like impulsivity was assessed with the Barratt Impulsiveness Scale (BIS-11). Affective symptoms were measured
using the Change version of the Schedule for Affective Disorders and Schizophrenia (SADS-C). Measures were compared using analysis of variance, multiple regression and
factor analysis. Results: Impulsivity, as measured by the BIS, was related differentially to measures of depression and mania. Total and attentional impulsivity
correlated independently with depression and mania scores. Motor impulsivity correlated with mania scores, while nonplanning impulsivity correlated with depression
scores. These relationships were strongest in subjects who had never met criteria for a substance use disorder. Among manic symptoms, visible hyperactivity correlated
most strongly with BIS scores, regardless of clinical state. Among depressive symptoms, hopelessness, anhedonia, and suicidality correlated most strongly with BIS
scores. Conclusions: Depression and mania are differentially related to impulsivity. Impulsivity is related more strongly to measures of activity or motivation than to
depressive or manic affect. The relationship between impulsivity and hopelessness may be an important factor in risk for suicide. © 2007 Elsevier B.V. All rights
reserved.
Keywords: Bipolar disorder; Impulsivity; Depression; Mania
1. Introduction
Impulsivity is related to mechanisms and consequences of affective symptoms. Its relationship to mechanism stems from its role in the initiation of action (Barratt and
Patton, 1983; Moeller et al., 2001). Impulsivity can be regardedas a predisposition to action without reflection or regard for consequences (Moeller et al., 2001).
Consequences of impulsivity include
Journal of Affective Disorders 106 (2008) 241–248
www.elsevier.com/locate/jad
☆ ThisstudywassupportedinpartbythePatR.Rutherford,Jr.Chairin Psychiatry (ACS) and by NIH grants RO1 MH 69944 (ACS), RO1 DA08425(FGM),andKO2DA00403
(FGM).WethankSabaAbutaseh, Glen Colton, Psy.D., Stacey Meier, and Mary Pham for their assistance. ⁎ Correspondingauthor.PatR.Rutherford,Jr.ProfessorandViceChair for
Research Department of Psychiatry and Behavioral Sciences University of Texas health Sciences Center at Houston 1300 Moursund Street, Room 270 Houston, Texas, 77030,
USA. Tel.: +1 713 50 2555; fax: +1 713 500 2557. E-mail address: Alan.C.Swann@uth.tmc.edu (A.C. Swann).
0165-0327/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jad.2007.07.011
substance abuse (Moeller et al., 2002; Swann et al., 2004),suicidalbehavior(Maseretal.,2002;Simonetal., 2001; Swann et al., 2005), and other serious behavioral
problems (Stanford and Barratt, 1992). There is little information about impulsivity and specific affective symptoms. Impulsivity is considered to be inherent in mania
and is a prominent part of its diagnostic criteria (First et al., 1996; Swann et al., 2001b). Impulsivity is complex, however, and specific relationships between manic
symptoms and specific aspects of impulsivity have not been investigated. In the case of depression, there is even less information. At first glance, depression may
appear less strongly related to impulsivity than mania is. Combinations of depression and impulsivity are important in suicidal behavior (Soloff et al., 2000), but
impulsivity in this situation may be related to manic symptoms (Swann et al., 2007). Interestingly, an epidemiological study found impulsive suicide attempts to be
associated with high Beck Hopelessness Scale scores but with low depression scores (Simon et al., 2001). One aspect of impulsivity, as measured by the Barratt
Impulsiveness Scale, is nonplanning impulsivity, or lack of sense of the future(Pattonetal.,1995).Thisaspectofimpulsivitymay be related to hopelessness and depression.
We have investigated relationships between specific aspects of impulsivity and affective symptoms in subjects with bipolar disorder who were depressed, manic, or not
experiencing a current episode. The selfrated Barratt Impulsiveness Scale has been extensively validated and provides an integrated measure of impulsivity. Its three
subscales measure cognitive, behavioral, and adaptive aspects of impulsivity (Patton et al., 1995). Our hypotheses were that depression and mania would be
differentially related to impulsivity, and that the strongest relationships would involve symptoms related to activation, rather than mood.
2. Methods
2.1. Subjects
Potential subjects, who were referred to the study by clinicians or who responded to advertisements that had been approved by the Institutional Review Board, were
fully informed ofthe procedures, risks, andbenefits of the study,andsignedinformedconsentdocuments,beforeany study-related procedures took place. The study was
approved by the Committee for the Protection of Human Subjects, the Institutional Review Board (IRB) for the UniversityofTexasHealthScienceCenteratHouston.All
subjectshadbipolarIdisorderaccordingtoDSM-IV.Of83
subjects eligible for the study, only data from the 74 subjects for whom the definite presence or absence of a historyofasubstanceoralcoholabusedisorderwereused.
Seventeen met DSM-IV criteria for depression, 16 for mania,and17foramixedstate.Twenty-foursubjectswere defined as interepisode, meaning that they did not meet criteria
for a depressive or manic episode and had not met criteria for an episode for at least 3 months. Forty-seven subjects had met DSM-IV criteria for a substance or
alcohol-use disorder in the past; no subjects met criteria currently. Subjects were required to have negative breathalyzer® and urine screens for drugs of abuse when
they were tested. Presence of a substance/alcohol abuse history was not related to clinical state at the time of the study (X 2 (df=3)=0.33,pN0.9).
2.2. Diagnostic and symptom measures
Diagnoses, including substance abuse or dependence, were rendered by the Structured Clinical Interview for DSM-IV(SCID)(Firstetal.,1996).Symptomswererated using the
Change version of the Schedule for Affective DisordersandSchizophrenia(SADS-C),whichisdesigned to measure depressive, manic, anxious, and psychotic symptoms
concomitantly (Spitzer and Endicott, 1978b). TheaugmentedversionoftheSADS-Cusedinthisandour previous work (Bowden et al., 1994) had all ten mania rating scale items
used in the full SADS (Endicott and Spitzer,1978;SpitzerandEndicott,1978a),ratherthanthe subset of five items in the conventional SADS-C (Spitzer and Endicott, 1978b).
Raters were trained in these instruments, using standard rating tapes and materials. Diagnoses were confirmed in consensus diagnostic meetings that included co-authors
A.C.S, F.G.M., and J.L.S.
2.3. Impulsivity
Impulsivity was assessed using the Barratt Impulsiveness Scale (BIS-11) (Barratt and Patton, 1983). This 30item self-rated scale has three oblique factors:
attentional/ cognitive, which measures toleration for cognitive complexity and persistence; motor, which measures the tendency to act on the spur of the moment; and
nonplanning impulsivity, which measures the lack of senseofthefuture(Pattonetal.,1995).Itemsareratedfrom 1 (absent) to 4 (most extreme). Non-psychiatric controls
generallyscoreintherangeof50–60(Swannetal.,2002).
2.4. Statistical methods
For normally distributed variables, we used analysis of variance or multiple linear regression analyses. If
242 A.C. Swann et al. / Journal of Affective Disorders 106 (2008) 241–248
criteria for normality were not met (Kolmogorov– Smirnov test) we used appropriate nonparametric statistics. Post-hoc comparisons, when appropriate analysis
ofvarianceinteractionsweresignificant,usedtheDuncan multiple range test. Comparisons of interest were based on main effects of mania or depression. For example, a main
effect of mania would imply that manic subjects would differ from interepisode subjects and depressed subjects would differ from mixed (depression + mania) subjects.
3. Results
3.1. Impulsivity and affective state
Interepisode subjects had mean SADS-C mania rating scale (MRS) score of 5.7±4.6 (SD) and depression scoreof7.9±4.8;formanicsubjects,MRSwas18.9±6.7
anddepression8.7±4.9;fordepressedsubjects,MRSwas 4.6± 4.9 and depression 24.6±4.9, and for mixed states, MRS was 17.9±7.9 and depression score was 22.4±7.3. Depression
and mania scores did not correlate significantly (r=−0.09, pN0.4). As shown in Table 1, BIS scores were increased in depressed, manic, and mixed, compared to
interepisode, subjects, but the specific BIS11scoresthatwereincreaseddependedonaffectivestate. Motor impulsivity appeared to be selectively related to mania,
nonplanning impulsivity more strongly related to depression, and attentional impulsivity similarly, and additively, related to both. No interactions between depressive
and manic states approached significance. Post hoc analysis showed that elevations in motor, attentional, and total impulsivity scores were associated with the manic
state, being higher in manic than in interepisode subjects and higher in mixed than in
depressed subjects. Nonplanning impulsivity was higher in depressed or mixed than in interepisode subjects. Substance abuse can have prominent effects on impulsivity
and its relationship to bipolar disorder (Swann et al., 2004). The 27 subjects who had never met criteria for a substance use disorder resembled the entire group, with
noninteracting main effects of depression and mania for total (F(mania)=11.9, p=0.0022);F (depression)=6,p=0.022;F(interaction)=0)),attentional (F(mania)=6.9, p=0.015;
F(depression)=5.6, p= 0.026); F(interaction)=0) and nonplanning impulsivity (F(mania)=5.6, p=0.027;F(depression)=8.1, p=0.009; F(interaction)=0.9). Motor impulsivity
was significantly increased in mania (F(mania)=15, p=0.0008), without a main effect of depression (F(depression)=1.1). Unlike the case with all subjects, both mania
and depression had significant main effects on nonplanning impulsivity in subjects without histories of substance use disorders. Results of post hoc analyses in
subjects without histories of a substance use disorder were essentially identical to the case for the entire group, except that the difference in Motor impulsivity
between manic and interepisode subjects was significant rather than being a trend. Among subjects who had definitely met criteria for a
substanceusedisorder,therewerenosignificanteffectsof affectivestateonBISscores(formaineffects,Fb1.8,for interactions, Fb0.8). Among all subjects, with substance use
disorder added to the ANOVA model, there were significant interactions between mania and substance abuse history for BIS total (F (1,63)=4.6, p=0.035) and motor score
(F(1,63)=5.7, p=0.02), reflecting a higher BIS score in interepisode subjects, and a smaller difference between manic and interepisodesubjects, with a history of a
substance use disorder (for BIS total score in subjects without histories of a substance use
Table 1 BIS scores and affective state State (n) Manic Depr. Total Attentional Motor Nonplanning Interepisode (24) −−74.5±15.2 20.0±4.3 27.7±6.5 27.0±6.6 Depressed
(17) − + 80.1±10.1 21.6±3.7 27.5±5.2 31.0±4.1 Manic (16) + − 82.4±14.5 21.6±4.6 30.9±6.5 29.9±6.5 Mixed (17) + + 88.7±13.0 24.8±4.0 31.3±5.3 32.6±4.8 2-way ANOVA F
(1,70) (p) Mania 6.8 (0.011) 6.2 (0.015) 6.4 (0.014) 2.9 (0.1) Depression 3.5 (0.07) 6.0 (0.017) 0 6.0 (0.017) Mania×depression 0.0 0.7 0 0.2 F(df=3, 70) 1-way ANOVA
(p) 4.1 (0.01) 4.88 (0.004) 2.51 (0.06) 3.31 (0.025) Post hoc (Duncan multiple range), pb0.05 Ibmanic Ibmixed Dbmixed Ibmixed Mbmixed Dbmixed Ibmanic (0.08) Ibmixed
Dbmixed Ibdepressed Ibmixed The “Manic” and “Depr.” columns show whether subjects met DSM-IV criteria for a manic or depressive episode. Post-hoc shows comparisons for
which pb0.05. Comparisons of interest were I (interepisode) vs manic, depressed, or mixed; Manic (M) vs mixed, and depressed (D) vs mixed.
243A.C. Swann et al. / Journal of Affective Disorders 106 (2008) 241 –248
disorder, interepisode 62.1±13 vs manic 75.0±9.1; for those with definite substance use disorder history, interepisode 81.1±13.4 vs manic 84.3±11.8). MRS in
interepisodesubjectsdidnotdifferbetweenthosewithout (6.7±4.8)andwith(5.1±4.4)historiesofasubstanceuse disorder (t (df=21)=0.5), so the higher BIS scores in
interepisode subjects with histories of substance use disorders were not due to higher residual mania scores.
3.2. Differential relationships between impulsivity and depression or mania
Multiple regression analysis, with BIS scores as dependent variables and depression and mania scores as independent variables, showed that both depression and mania
scores contributed significantly to BIS total and attentional scores. Mania,but not depression, contributed to BIS motor scores, while depression, but not mania,
contributed to BIS nonplanning scores. Table 2 summarizes the data for the 27 subjects who had never met criteriaforasubstanceusedisorder.Theentiregroupof74 subjects,
including the 47 with a substance use disorder, had exactly the same pattern of significant relationships. When age of onset, substance use history, and treatment with
antipsychotic medicines, lithium, anticonvulsants, and antidepressants were taken into account, the same relationships as those in Table 2 persisted.
3.3. Impulsivity and affective symptoms
In order to investigate relationships between individual depressive or manic symptoms and impulsivity, we conducted a principal components analysis of SADS-C items to
determine which symptoms contributed most to depression and mania in these subjects. After varimax rotation, four factors accounted for over half the variance. The
factors were 1) Depression, consisting, in order of strength of loading, subjective depression, anhedonia, hopelessness, negative self
evaluation, worry, fatigue, somatic anxiety, self-reproach, and suicidality (eigenvalue 5.2, 20.2% of variance); 2) Mania, consisting of increased energy, elevated
mood, visible hyperactivity, accelerated speech, grandiosity, increased goal-directed activity, decreased need for sleep, and racing thoughts (eigenvalue 5.9, 18.9% of
variance); 3) Psychosis, consisting of delusions, hallucinations, and paranoia (eigenvalue 2.3, 8.8% of variance); and 4) Hostility, consisting of overt irritability,
overt anger, and subjective irritability (eigenvalue 2.2, 8.4% of variance). For all subjects (n=74), attentional impulsivity correlated significantly with depression
(r=0.28, p=0.015) and mania factor (r=0.25, p=0.03) scores, motor impulsivity correlated with mania factor scores (r=0.24, p=0.04) and nonplanning impulsivity
correlated with depression factor scores (r=0.24, p=0.04). There were no significant correlations between BIS scores and hostility or psychosis factor scores. For
subjects without history of a substance use disorder (n=27), attentional impulsivity correlated significantly with depression (r=0.42, p=0.03) scores, motor
impulsivity correlated with mania scores (r=0.39, p=0.04), and nonplanning impulsivity correlated with depression scores (r=0.44, p=0.02). The pattern of multiple
regression correlation coefficients for the mania and depression factors was exactly the same as that shown in Table 2 for mania and depression subscale scores. We
then investigated relationships between BIS scores and the rating scores for the symptoms loading most strongly to depression or mania, in all subjects having an
episode, depressed subjects, and manic subjects. Table 3 shows that, among manic symptoms in all subjects having episodes, visible hyperactivity
correlatedmoststronglywithBISscores.Thereweresignificant but more modest correlations with increased energy and accelerated speech. In manic episodes, visible
hyperactivity correlated significantly with attentional (Kendall tau=0.306) and motor (Kendall tau=0.265) scores; no
Table 2 Multiple linear regression analyses of BIS, depression, and mania subscale scores in subjects with bipolar disorder but without substance use disorders Score
Overall F (2,24) Multiple R2 MRS (p) Depression (p) Beta Partial R Beta Partial R Total 4.8 (0.018) 0.270 0.415 (0.02) 0.432 0.386 (0.03) 0.407 Attentional 4.6 (0.021)
0.261 0.387 (0.04) 0.406 0.401 (0.03) 0.418 Motor 4.3 (0.03) 0.247 0.473 (0.02) 0.474 0.243 (0.2) 0.266 Nonplanning 3.5 (0.044) 0.212 0.275 (0.2) 0.293 0.416 (0.026)
0.420 Statistical significances of F ratios or beta coefficients are in parentheses. MRS is the Mania Rating Scale score derived from the SADS-C. “Depression” is the
depression factor score derived from the SADS-C.
244 A.C. Swann et al. / Journal of Affective Disorders 106 (2008) 241–248
other symptoms correlated with BIS scores. Visible hyperactivity was also the only manic symptom correlating with BIS scores among depressed subjects, where
itcorrelatedsignificantly with total (Kendalltau=0.424), attentional (Kendall tau=0.408) and motor scores (Kendall tau=0.408). As was the case with mania, subjective
depressive mooditselfdidnotcorrelatewithBISscores.Hopelessness andanhedoniacorrelatedsignificantlywithBISattentional scores in all subjects and in subjects
experiencing manic episodes. Suicidality also correlated modestly but significantlywithBISattentionscoresforsubjectsindepressive ormanicepisodes
(Kendalltau=0.175,p=0.03)andinall subjects (Kendall tau=0.192, p=0.02).
4. Discussion
4.1. Definitions and components of impulsivity
Impulsivity defines behavior that occurs without the opportunity for reflection and is therefore not consistent with its context (Moeller et al., 2001). The BIS-11
identifies three components of impulsivity. Attentional/ cognitive impulsivity is a lack of cognitive persistence with inability to tolerate cognitive complexity;
motor impulsivity is a tendency to act on the spur of the moment; and nonplanning impulsivity refers to a lack of sense of the future (Patton et al., 1995).
Thedatainthispapershowthatthethreecomponents of impulsivity as measured by the BIS (Patton et al., 1995) were related differentially to affective state. Attentional
impulsivity was related to either depression or mania, motor impulsivity to mania, and nonplanning impulsivity to depression. Previous reports have suggested that
attentional impulsivity was increased in individuals with an Axis I psychiatric disorder (Swann et al., 2002), motor impulsivity was increased in subjects with bipolar
disorder who also had impulse control disorders (Lejoyeux et al., 2002), and nonplanning impulsivity was increased in subjects (generally not having bipolar disorder)
with personality disorders (Dougherty et al., 2000). BIS subscales are also related differentially to other measures of impulsivity. In a sample of non-impulsive
controls, motor impulsivity correlated with performance on a stop-signal task, consistent with impaired motor inhibition, nonplanning impulsiveness correlated with
complex reaction time, taken as impaired response organization, and cognitive impulsivity correlated somewhat more weakly with errors in time production, consistent
with impaired temporal regulation (Gorlyn et al., 2005). Among a group of subjects ranging more widely in impulsivity, we found BIS nonplanning and motor impulsivity
to correlate with performance on tests of ability to delay reward and nonplanning impulsivity to correlate with increased commission errors on a continuous performance
task (Swann et al., 2002).
4.2. Impulsivity and mania
Impulsivityisaconsistent,centralfeatureofotherwise heterogeneous manic episodes (Swann et al., 2001b). As shown in Table 3, the aspect of mania that appeared the most
strongly related to BIS scores was hyperactivity, rather than subjective mood symptoms. Total, attentional and motor BIS scores are increased in subjects with
bipolardisorder,regardlessofaffectivestate(Swannetal., 2001a), though the data in this paper suggest that even in interepisode bipolar disorder increased BIS scores
are due, at least in part, to subsyndromal symptoms of depressionormania(Table1 andrelatedresults).Further, total BIS scores appear to be increased additively by the
presence of bipolar disorder and a substance use disorder (Swannetal.,2004),andthedatainthispapershowsthat history of a substance use disorder contributes to
impulsivity in interepisode subjects independent of residualmanicsymptoms(seeTable1 andrelatedresults). All three BIS scores were increased in mania, but
increasedmotorimpulsivityappearedspecifictomania. The increased motor impulsivity in mania is consistent
Table 3 Correlations between manic or depressive symptoms and BIS scores Score BIS Total BIS attentional BIS motor BIS nonplanning Mania items Increased energy 0.188⁎
0.181⁎ 0.196⁎ 0.096 Elevated mood 0.017 −0.006 0.096 −0.096 Visible hyperactivity 0.297⁎⁎ 0.326⁎⁎ 0.313⁎⁎ −0.085 Accelerated speech 0.148 0.169⁎ 0.174⁎ 0.085 Grandiosity
−0.083 −0.085 0.031 −0.159⁎
Depression items Subjective depression
0.087 0.121 −0.025 0.139
Anhedonia 0.114 0.221⁎⁎ −0.026 0.134 Hopelessness 0.226⁎⁎ 0.238⁎⁎ 0.146 0.236⁎⁎ Negative eval. of self 0.081 0.018 0.083 0.141 Worry 0.003 0.112 −0.075 0.030 Symptoms are
those loading most strongly on the mania or depression factors in factor analysis of the SADS-C (see text). Kendall tau: ⁎pb0.05; ⁎⁎pb0.01.
245A.C. Swann et al. / Journal of Affective Disorders 106 (2008) 241 –248
with the association between motor impulsivity and bothimpetuousnessandventuresomeness(Milleretal., 2004). We reported motor impulsivity to be related to inability to
delay a reward-related response (Swann et al., 2002), and Gorlyn et al showed it to be related to impairedstop-signalreactiontime(Gorlynetal.,2005),
consistentwithinabilitytowithholdortomodifymotor responses. The BIS is intended to measure impulsivity as a stable trait, but has been reported to be influenced by
clinical state as well (Corruble et al., 2003)(Table 1). Thereisinadequatelongitudinaldatatodifferentiatethe relative roles of true state-dependence as opposed to
differences among patients with bipolar disorder predisposed to having more severe or recurrent illness and therefore more likely to be symptomatic when they were
studied. For example, elevated impulsivity scores couldreflectneurotoxicityresultingfrompreviousdrug exposure (Moeller et al., 2005) or from multiple episodes of
illness (Post et al., 1986). In the multiple regression analysis in Table 2, the extrapolated yintercept for total BIS (ie, MRS and depression scores=0) was 60.9±14.7
for subjects without substance use disorder history and 73.9±13.0 for subjects with histories of a substance use disorder, similar to values we have previously
reported for comparable subjects without bipolar disorder (Swann et al., 2004). Many potential mechanisms underlie impulsivity (Evenden, 1999). Attention deficit
disorder, like bipolar disorder, is associated with impulsivity and increased motor activity, but their mechanisms and psychopharmacology differ (Evenden, 1999;Faraone
et al., 2000). These differences reveal the importance in understanding the neurobiology of symptoms in different clinical contexts in order to develop rational
treatments (Moeller et al., 2001).
4.3. Impulsivity and depression
There is evidence supporting a relationship between impulsivity and depression, as well as mania. Impulsivity in depressed patients could be a result of coexisting
manic symptoms (Swann et al., 2007). Kraepelin defined “excited depression” as a mixed state where excitability and hyperactivity, rather than elevated mood, were
prominent, consistent with mixed depressive subjects described by Akiskal et al. (Akiskal et al., 2005) and with the results in Table 3. Impulsivity could also be a
component of the depressive state itself. Corruble et al., for example, have characterized impulsivity in nonbipolar subjects with major depressive episodes (Corruble
et al., 2003). Using
the BIS and other questionnaires, this group described increased attentional, behavioral, and nonplanning impulsivity in subjects experiencing depressive episodes
(Corruble et al., 2003). Among non-bipolar subjects with methamphetamine abuse, Beck depression scale scores were increased in the subjects with high impulsivity
(Semple et al., 2005). In the current study, Table 3 shows that, among depressed subjects, BIS scores correlated most strongly with hopelessness and anhedonia, rather
than subjective depression. Nonplanning impulsivity was related more strongly to depression than to mania. Patton et al formulated nonplanning impulsivity as lack of a
sense of the future (Patton et al., 1995). The relationship that we reported between nonplanning impulsivity and inability to delay reward-related responses is
consistent with this lack of future sense (Swann et al., 2002), as is the correlation between nonplanning impulsivity and hopelessness or anhedonia (Table 3). These
data raise the question of the extent to which impulsivity in depressed subjects is related to the presence of subtle manic symptoms in mixed depressive states
(Akiskal et al., 2005). The multiple regression analyses in Table 2 show that BIS scores correlated independently with depression and mania scores. Therefore, beyond
the increased impulsivity associated withmanicsymptomsinmixeddepressivestates(Swann et al., 2007), a component of impulsivity appears intrinsic to the depressive state
itself.
4.4. Impulsivityanddepression:relationshiptosuicidality
Theoretical (Fawcett, 2001; Mann et al., 1999), epidemiological (Simon et al., 2001), and clinical (Dumais et al., 2005; Swann et al., 2005) studies suggest that
depression or hopelessness can interact with impulsivity to result in risk for suicide. A fourteen-year prospectivestudyfoundthatnearlylethalsuicideattempts and
completed suicide were associated with impulsivity, substance abuse, previous attempts, and a cycling/mixed clinical presentation, with trait impulsivity predicting
suicide even more than 12 months later (Maser et al., 2002).Inmajordepressivedisorder,impulsiveaggression was associated with greater risk for completed suicide
(Conner et al., 2001; Dumais et al., 2005). Hopelessness or anhedonia may be more directly related to suicidality than depressed mood is. Reduced
P300amplitude,aneurophysiologicparameterassociated with impulsivity and behavioral disinhibition (Iacono et al., 2003), correlated with suicidality and hopelessness
but not with depressed mood (Hansenne et al., 1996). A case-control study of medically severe suicide attempts
246 A.C. Swann et al. / Journal of Affective Disorders 106 (2008) 241–248
found that attempters with predominately impulsive attempts (more likely to be violent) had elevated Beck Hopelessness Scale scores comparable to subjects with planned
attempts but did not have elevated depression (CES-D) scores compared to controls (Simon et al., 2001). In the current study, suicidality (SADS-C) correlated with
attentional impulsivity. Attentional impulsivity represents intolerance for complexity, characterizedbyimpatienceandlackofflexibility (Pattonetal.,
1995).Thisisconsistentwithreportsthatsuicideattempts with a large impulsive component were characterized by seemingly minor precipitants, and relatively low
expectation of death despite use of violent methods (Peterson et al., 1985; Simon et al., 2001). A few studies have investigated BIS scores in depressed patients in
relationship to suicidal behavior. Corruble et al described increased cognitive, behavioral, and nonplanning impulsivity in patients with major depressive episodes,
but only cognitive (attentional) impulsivity was associated with history of suicide attempts (Corruble et al., 2003), consistent with our results. In subjects with
bipolar disorder, increased BIS scores were associated with symptoms of cluster B personality disorders, suicidal behavior, and early-life stressors (Garno et al.,
2005).
4.5. Limitations
This was a cross-sectional study and there are no measurements of duration, or order of appearance, of symptoms, or of temporal stability of BIS scores. The small
sample size limited some analyses. While demographically similar to other populations with bipolar disorder, the subjects may have differed from individuals in the
community who did not volunteer.
5. Conclusions
Impulsivity appears differentially related to depressive and manic symptoms. Attentional-cognitive impulsivity is increased with either depression or mania; motor
impulsivity correlates with mania, and nonplanning impulsivity with depression. Impulsivity correlated most strongly with hyperactivity in mania and with hopelessness
or anhedonia in depression, reflecting the possibility of a stronger relationship to motivation or activity than to subjective affect.
Role of the funding source This work was supported by the Pat R. Rutherford, Jr. Chair in Psychiatry (ACS) and by NIH grants RO1 MH 69944 (ACS; principal source of
funding), RO1 DA 08425 (FGM), and KO2 DA 00403
(FGM). The funding sources were not involved in design of the studies, analysis or interpretation of the data, preparation of the manuscript, or decision to publish
the manuscript.
Disclosure of potential conflicts of interest ACS: grant support: Bristol Myers Squibb, Novartis, Shire Labs
Consultantoradvisoryboard:AbbottLaboratories,AstraZeneca,Bristol MyersSquibb,Cyberonics,GlaxoSmithKline,Novartis,OrthoMcNeill, Pfizer, Shire Labs Speakers bureau or
sponsored lectures: Abbott laboratories, Astra Zeneca, Glaxo SmithKline.
JLS: None ML: None FGM: grant support: Ortho McNeill Acknowledgements
This study was supported in part by the Pat R. Rutherford, Jr. Chair in Psychiatry (ACS) and by NIH grants RO1 MH 69944 (ACS), RO1 DA08425 (FGM), and KO2 DA00403
(FGM). We thank Saba Abutaseh, Glen Colton, Psy.D., Stacey Meier, and Mary Pham for their assistance.
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