Physiology & Behavior 105 (2012) 332–336

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Physiology & Behavior

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Dopamine activation in Neuroticism as measured by spontaneous eye blink rate

Giuseppe Barbato ⁎, Ciro della Monica, Antonio Costanzo, Vittoria De PadovaDepartment of Psychology, Second University of Naples, Via Vivaldi 43, 81100 Caserta, Italy

⁎ Corresponding author. Tel.: +39 0823 274790; fax:E-mail address: Giuseppe.Barbato@unina2.it (G. Bar

0031-9384/$ – see front matter © 2011 Elsevier Inc. Aldoi:10.1016/j.physbeh.2011.08.004

a b s t r a c t

a r t i c l e i n f o

Article history:Received 1 June 2011Received in revised form 1 August 2011Accepted 6 August 2011

Keywords:Personality dimensionsDopamineEye blink rateActivationNeuroticismDepression

Personality dimensions have been associated with different psychobiological systems. However, noagreement exists in literature on a specific role of a single neurotransmitter for each of the dimensionsinvestigated. We studied the relationship of Neuroticism, Extraversion and Psychoticism as assessed byEysenck Personality Inventory (EPI) with spontaneous eye blink rate (BR), a non-invasive measure of centraldopamine activity. A total of sixty-three healthy subjects (40 females, 23 males, mean age 24.2±3.9) werestudied. Spontaneous blink rate and time of blink suppression were assessed by EOG measurement.Levels of Extraversion and Neuroticism were inversely correlated. In contrast with previous findings, asignificant correlation between blink rate measures and Neuroticism was found. No significant correlationbetween blink measures and either Extraversion, or Psychoticism were found. The results appear consistentwith a lower threshold for activation in neuroticism as suggested by Eysenck's original model.

+39 0823 274792.bato).

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1. Introduction

Eysenck's theory of personality describes three major personalitydimensions:Neuroticism, Extraversion andPsychoticism [1,2]. Differentpsychobiological systems have been suggested for these dimensions.According to Eysenck, Neuroticism is based on the biological systemwhich relates to the visceral brain (the hippocampus-amygdala,cingulum, septum, andhypothalamus) and produces autonomic arousal[2,3] while Extraversion is conceived as a product of the functioning ofthe reticular activating system and produces cortical arousal [4].

Eysenck's theory originally incorporated Hebb's [5] concept of an“optimal level of arousal” for maximum performance. According toEysenck [2], Introverts and Extraverts are characterized by differentlevels of basal arousal. Introverts were theorized to have a higher than“optimal” level of basal arousal and Extraverts to have a lower than“optimal” level [6].

Psychoticism has been associated to dopamine (DA) functioning[7]. Recently, Colzato et al. [8] have used eye blink rate (BR), ameasureof DA functioning [9–11], to test DA activity in personality dimensions.A significant correlationwas found between high BR and subjects witha high score at the Psychoticism scale. Colzato et al. [8], have suggestedthat individual differences in dopaminergic activity represent a con-tinuumwith schizophrenia at one end and low Psychoticism scores atthe other end.

Previous studies have however suggested a possible link betweendopaminergic system and Neuroticism. Striatal D2 receptor densities,

as measured by single photon emission computed tomography with[(123)I] iodo-benzamide, were significantly correlated with theNeuroticism score [12].

An association between short allele of the dopamine D4 receptor(DRD4) and higher scores for Neuroticism, has been reported in theJapanese population [13]. Dragan and Oniszczenko [14] showed thatthere is an interaction between DRD4 and DA transporter gene (DAT1)polymorphisms and Neuroticism in a Polish female population. Jönssonet al. [15] demonstrated that the D2 receptor gene (DRD2) is associatedwith Neuroticism-related scales. Waker et al. [16] showed anassociation between DRD2 polymorphism and Neuroticism.

Considering that the dopaminergic system has been linked either toPsychoticism or to Neuroticism, we aimed to replicate the results byColzato et al. [8] in investigating whether Eysenck's personality di-mensions could relate to different levels of DA activation, as measuredby spontaneous eye blink rate.

2. Method

Sixty-three subjects (40 females, 23 males), age 18–38 years(24.27±3.98), were included in the study. The study was conductedin accordancewith the ethical standards of the declaration of Helsinky.All subjects provided their informed consent. To exclude subjects withrelevant sleep impairments, use of psychotropic drugs, and with anykind of substance abuse, a questionnaire assessing life and sleep habitswas administered to all subjects. According to psychiatric clinicalinterviews, performed by one (G.B.) of the authors, all subjects had nohistory of psychiatric illnesses (DSM IV, Axis I), had normal physicalexaminations before the study andwere not affected by any significantmedical, psychiatric, neurological or ophthalmological illness. Subjects

Fig. 1. Relationship between level of Neuroticism and level of Extraversion.

333G. Barbato et al. / Physiology & Behavior 105 (2012) 332–336

whowere wearing contact lenses or who were suffering at the time oftesting from a cold, flu, headache, or any condition interfering withvisual sensitivity were excluded. Demographic statistics are shown inTable 1.

Vertical and horizontal electro-oculograms (EOGs) were recordedon a Grass Model 78 polygraph. Gold skin electrodes were placed3.0 cm above and 2.0 cm below the left eye as measured from thecenter of pupil to the center of the electrode (vertical EOG), and at theouter canthi (horizontal EOG). Eye blink was defined as a sharp highamplitude wave ≥100 μV, peaking from the baseline in no more than100 ms, and ≤400 ms in duration [17]. High amplitude wavescoincident with horizontal eye movements were not counted asblinks. EOG records were obtained in an air conditioned room withindoor light of 150 lux at the level of the subject's eye. During the eyeblink recording, each subject sat silently in front of a blank, neutralwall. The subject was asked to remain awake, so that we could studybasal ocular activity. BRwas taken as themean number of blinkswhichoccurred during the 2 min following a 4 min accommodation period,subjects were unaware of the accommodation period. Subjects alsoperformed a blink suppression time (BST) test, trying to stop blinkingthe longer time possible. This time intervalwas defined by the numberof seconds from the end of eye blink to the first eye movementoccurring during the suppression task. Before the recording session,subjects were administered the Eysenck Personality Inventory (EPI),adult form, which includes 23 items for Psychoticism, 21 items forExtraversion and 23 items for Neuroticism [18]. Spearman analysis ofcorrelation was used to assess correlations between the eye blinkrate and the eye blink suppression time, and between personalitydimensions and blink measures.

3. Results

Neuroticism scores ranged from 1 to 19 (9.4±5.05), Extraversionfrom 5 to 19 (12,84±3,50), Psychoticism from 1 to 10 (4.63±2.07).Females showed higher score than males for Neuroticism (t=.266,p=.010), no significant differences were found between males andfemales for all the other variables. A significant negative correlationbetween Neuroticism and Extraversion (rho=− .320, p=.011) wasfound (Fig. 1); no significant correlations were found between theother personality dimensions.

BR correlated positively with Neuroticism (rho=.348, p=.005);BST correlated negatively with Neuroticism (rho=−.384, p=.002)(Fig. 2), and with BR (rho=− .355, p=.005). Whole correlations areshown in Table 2.

4. Discussion

In our study a significant inverse correlation between Neuroticismand Extraversion scores was found. Subjects with higher levels ofNeuroticismhad lower levels of Extraversion. Thisfinding is consistentwith Eysenck's theory [2], who originally suggested that Neuroticismand Extraversion are located at different points of the personalitystructure.

Our results of the physiological variables investigated, spontaneouseye blink rate and time of blink suppression, showed respectively a

Table 1Demographic characteristics. Means and standard deviation.

Male Female t Sig. Total sample

N 23 40 63Age 24.1±2.7 24.3±4.6 .209 .835 24.27±3.98Neuroticism 7.3±4.8 10.6±4.8 .266 .010 9.40±5.05Extraversion 13.5±3.3 12.5±3.6 −1.095 .278 12.84±3.50Psychoticism 4.4±1.9 4.8±2.2 .704 .484 4.63±2.07BR 15.7±8.5 19.8±8.6 1.817 .074 18.3±8.7BST 30.7±26.9 20.1±22.1 −1.670 .100 23.9±24.3

significant positive and a significant negative correlation withNeuroticism. These findings appear consistent with the supposedlower threshold for “activation” in neuroticism as suggested byEysenck's model [19–21].

BR is a non-invasive measure of DA central activity [10]. Clinicaldata in patients with DA-related dysfunctions support the idea that BRreflects dopaminergic functions. BRs are elevated in patients withschizophrenia [10,22,23], who in PET studies demonstrate elevatedstriatal DA uptake [24,25]. Conversely, BRs are reduced in Parkinson'spatients [9,26] who suffer from severe losses of nigrostratialdopaminergic cells [27], and in recreational cocaine users [28] whoshow reduced functioning of D2 receptors [29]. Pharmacologicalstudies in humans and primates have shown that DA agents inducepredictable changes in BR [30–32].

BR is also sensitive to psychophysiological factors. In their seminalwork, Ponder and Kennedy [33] implicated higher nervous processesas the major determinant of blink enhancement and inhibition.Higher levels of activation or arousal are associated with elevatedblink rate [34]. Blinks occur more frequently when subjects performtests involving higher levels of attention [35,36], and an increased BRis associated with higher level of electroencephalographic (EEG)activation [35].

Recent studies have suggested that DA is also implicated in thewakearousal control. Barbato et al. [11,37] have reported that BR increasesafter sleep deprivation, suggesting an activation of the DA system, tomaintain wakefulness and counteract a rising sleep drive [37,38].Volkowet al. [39] have shown a significant reduction of [11 C]Raclopride(a radiotracer that is sensitive to competition with endogenous DA tomeasure changes in DA [40]) in the striatum and thalamus after sleepdeprivation, and that the magnitude of this reduction correlated withincreases in fatigue (tiredness and sleepiness) andwith deterioration incognitive performance (visual attention and working memory). Thus,DA increases may occur to maintain arousal as the drive to sleepincreases [37,39].

According to our present results Neuroticism appears to show anincreased level of DA activation as measured by BR.

Our results are in contrast with previous study on BR andpersonality dimensions, which reported a significant correlation ofBR with the Psychoticism personality dimension [8]. Differencesbetween our results and Colzato et al.'s [8] results can mainly beattributed to differences in methodology between the two studies.

To assess personality dimensions we used the EPI [18], whereasColzato et al. [8] used the Eysenck Personality Questionnaire Revised

Fig. 2. Relationship between levels of Neuroticism and eye blink rate (left panel). Relationship between levels of Neuroticism and blink suppression time (right panel).

334 G. Barbato et al. / Physiology & Behavior 105 (2012) 332–336

Short Scale (EPQ-RSS). According to Roger and Morris [41], thePsychoticism scale in the EPQ reflect a diverse range of constructs andincludes some impulsivity items from the EPI Extraversion [20]. Forthe eye blink measures, we recorded spontaneous blink rate while thesubject was looking at a neutral wall, whereas Colzato et al. [8] had thesubjects forced to fix a point during the recording period.

A possible confounding of the present results is the gender effecton both the personality and the physiological variables investigated.Previous studies have shown that females have higher Neuroticismscores than males [42–47], and females appear also to have a higherBR than males [48].

Although in our sample females had higher Neuroticism score thanmales, no significantdifferences betweenmales and femaleswere foundfor the blinkmeasures. It is advisable that future studies will specificallyaddress the role of gender inmodulating the physiological – personalityassociation.

The second eye-blink parameter analyzed in the present study wasthe duration of voluntary suppression of eye blinking. As reported inprevious studies [37,38] blink rate correlate inversely with blinksuppression time. Consistent with results on BR, a significant inversecorrelation between BST and Neuroticism was found.

As proposed by Eysenck [2,19,20], Neuroticism results froma lowerthreshold for activation in the limbic system [21]. Eysenck [2,20]suggested two principal brain systems as the key components in

Table 2Spearman's correlations between personality dimensions, Blink Rate (BR) and Blink Suppre

PSYCHOTICISM EXTRA

PSYCHOTICISM rho 1.000 .172p . .178N 63 63

EXTRAVERSION rho .172 1.000p .178 .N 63 63

NEUROTICISM rho .156 − .320p .223 .011N 63 63

BR rho .099 − .242p .441 .056N 63 63

BST rho − .232 .064p .075 .627N 60 60

nervous system: reticulo-cortical and reticulo-limbic circuits. Thereticulo-cortical circuit controls the cortical arousal generated byincoming stimuli, whereas the reticulo-limbic circuit controls re-sponse to emotional stimuli; under strong emotional stimulation,limbic system activity may spread to the cortex [49].

Since BR appears to mainly reflect striatal DA activity [9,30–32,50,51], it might be hypothesized that DA activation in Neuroticismis located at subcortical level, however the role of cortical structures inmediating DA activation in Neuroticism cannot be excluded.

Haas et al. [52] have hypothesized that sustained activation inresponse to negative stimuli may serve as a neural substrate ofNeuroticism, possibly located in theMedial Prefrontal Cortex (MedPFC).

Recent studies have also showed neuro-anatomical differencesbetween Neuroticism and Extraversion. Wright et al. [53] observedthat the thickness of specific prefrontal cortex regions correlates withmeasures of Extraversion and Neuroticism, Deckersbach et al. [54]found significant negative correlations between Neuroticism andrCMRglu in the insular cortex and positive correlations betweenExtraversion and rCMRglu in the orbitofrontal cortex.

Eisenberger et al. [55] suggest that the reactivity of the dorsalanterior cingulate cortex (dACC) is directly related toNeuroticism, dueto its role in discrepancy detection, whereas the reactivity of neuralregions involved in other aspects of controlled processing are moreclosely related to Extraversion and self-consciousness.

ssion Time (BST).

VERSION NEUROTICISM BR BST

.156 .099 − .232

.223 .441 .07563 63 60− .320 − .242 .064.011 .056 .62763 63 601.000 .348 − .384. .005 .00263 63 60.348 1.000 − .355.005 . .00563 63 60− .384 − .355 1.000.002 .005 .60 60 60

335G. Barbato et al. / Physiology & Behavior 105 (2012) 332–336

Several authors have suggested that Neuroticism, which appearsas the core of internalizing psychopathology [56,57], could be apsychological risk factor to develop either anxiety and depression.Jylha et al. [58] have reported that Neuroticism is strongly associatedwith depressive and anxiety symptoms, Clark et al. [59] have foundthat Negative affectivity (or Neuroticism) appears to be a vulnerabilityfactor for the development of anxiety and depression, and Brühl et al.[60] have recently shown that Neuroticism was correlated withdepression and anxiety disorders, implicating a common neurobio-logical basis.

Higher levels of Neuroticism or emotional instability have alsobeen suggested as risk factors for the later initiation and developmentof a substance abuse disorder [61–65].

Measurement of spontaneous blink rate could thus be a useful andnon invasive methodology to assess sensitivity of the DA activitysystem and provide a psychobiological tool to identify vulnerability ofthe subjects to a major psychiatric condition.

References

[1] Eysenck HJ. The scientific study of personality. London: Routledge and Kegan Paul;1952.

[2] Eysenck HJ. The biological basis of personality. Springfield: IL: C. C. Thomas; 1967.[3] Eysenck HJ. Biological dimensions of personality. In: Pervin L, editor. Handbook of

personality theory and research. New York: Guilford Press; 1990. p. 244–76.[4] Schmidtke JI, Heller W. Personality, affect and EEG: predicting patterns of regional

brain activity related to extraversion and neuroticism. Pers Individ Differ 2004;36:717–32.

[5] Hebb DO. Drives and the C.N.S. (conceptual nervous system). Psychol Rev1955;62:243–54.

[6] Taylor DJ, McFatter RM. Cognitive performance after sleep deprivation: doespersonality make a difference? Pers Individ Differ 2003;33:1179–93.

[7] Lester D. A neurotransmitter basis for Eysenck's theory of personality. Psychol Rep1989;64:189–90.

[8] Colzato LS, Slagter HA, van den Wildenberg WPM, Hommel B. Closing one's eye toreality: evidence for a dopaminergic basis of Psychoticism from spontaneous eyeblink rates. Pers Individ Differ 2009;46:377–80.

[9] Karson CN. Spontaneous eye blink rate and dopaminergic system. Brain 1983;106:643–53.

[10] Karson CN, Dykman R, Paige SR. Blink rates in schizophrenia. Schizophr Bull1990;16:345–54.

[11] Barbato G, Ficca G, Beatrice M, Casiello M, Muscettola G, Rinaldi F. Effects of sleepdeprivation on spontaneous eye blink rate and alpha EEG power. Biol Psychiatry1995;38:340–1.

[12] Lee IH, Cheng CC, Yang YK, Yeh TL, Chen PS, Chiu NT. Correlation between striataldopamine D2 receptor density and neuroticism in community volunteers.Psychiatry Res 2005;138:259–64.

[13] Tochigi M, Hibino H, Otowa T, Kato C, Marui T, Ohtani T, et al. Association betweendopamine D4 receptor (DRD4) exon III polymorphism and Neuroticism in theJapanese population. Neurosci Lett 2006;398:333–6.

[14] Dragan WL, Oniszczenko W. An association between dopamine D4 receptor andtransporter gene polymorphisms and personality traits, assessed using NEO-FFI ina Polish female population. Pers Individ Differ 2007;43:531–40.

[15] Jonsson EG, Cichon S, Gustavsson JP, Grunhage F, Forslund K, Mattila-Evenden M,et al. Association between a promoter dopamine D2 receptor gene variant and thepersonality trait detachment. Biol Psychiatry 2003;53:577–84.

[16] Wacker J, Reuter M, Hennig J, Stemmler G. Sexually dimorphic link betweendopamine D2 receptor gene and neuroticism-anxiety. Neuroreport 2005;16:611–4.

[17] Barbato G, Fichele M, Senatore I, Casiello M, Muscettola G. Increased dopaminergicactivity in restricting-type anorexia nervosa. Psychiatry Res 2006;142:253–5.

[18] Eysenck H, Eysenck S. Manual of the EPI. University of London; 1964.[19] Eysenck HJ. A model for personality. New York: Springer; 1981.[20] Eysenck HJ, Eysenck M. Personality and individual differences: a natural science

approach. New York: Plenum Press; 1985.[21] Rusting CL, Larsen RJ. Extraversion, Neuroticism, and susceptibility to positive and

negative affect: a test of two theoretical models. Pers Individ Differ 1997;22:607–12.

[22] Freed WJ. Eye-blink rates and platelet monoamine oxidase activity in chronicschizophrenic patients. Biol Psychiatry 1980;15:329–32.

[23] Stevens JR. Eye blink and schizophrenia: psychosis or tardive dyskinesia? Am JPsychiatry 1978;135:223–6.

[24] Hietala J, Syvälahti E, Vilkman H, Vuorio K, Räkköläinen V, Bergman J, et al.Depressive symptoms and presynaptic dopamine function in neuroleptic-naiveschizophrenia. Schizophr Res 1999;35:41–50.

[25] Lindström LH, Gefvert O, Hagberg G, Lundberg T, Bergström M, Hartvig P, et al.Increased dopamine synthesis rate in medial prefrontal cortex and striatum inschizophrenia indicated by-([beta]-11c) dopa and pet. Biol Psychiatry 1999;46:681–8.

[26] Deuschel G, Goddemeier C. Spontaneous and reflex activity of facial muscles indystonia, Parkinsonís disease, and in normal subjects. J Neurol NeurosurgPsychiatry 1998;64:320–4.

[27] Dauer W, Przedborski S. Parkinson's disease: mechanisms and models. Neuron2003;39:889–909.

[28] Colzato LS, van den Wildenberg WP, Hommel B. Reduced spontaneous eye blinkrates in recreational cocaine users: evidence for dopaminergic hypoactivity. PLoSOne 2008;3:e3461.

[29] Volkow ND, Fowler JS, Wang GJ. Imaging studies on the role of dopamine incocaine reinforcement and addiction in humans. J Psychopharmacol 1999;13:337–45.

[30] Blin O, Masson G, Azulay J, Fondarai J, Serratrice G. Apomorphine-induced blinkingand yawning in healthy volunteers. Br J Clin Pharmacol 1990;30:769–73.

[31] Kleven MS, Koek W. Differential effects of direct and indirect dopamine agonistson eye blink rate in cynomolgus monkeys. J Pharmacol Exp Ther 1996;279:1211–9.

[32] Jutkiewicz EM, Bergman J. Effects of dopamine D1 ligands on eye blinking inmonkeys: efficacy, antagonism, and D1/D2 interactions. J Pharmacol Exp Ther2004;311:1008–15.

[33] Ponder E, Kennedy W. On the act of blinking. Exp Physiol 1927;18:89–110.[34] Stern JA, Walrath LC, Goldstein R. The endogenous eyeblink. Psychophysiol

1984;21:22–33.[35] Gille HG, von Otto O, Ullsperger P. Aktivierungs- Abhangigkeit, Anfoderunsspe-

cifitat und Zeitverhalten Physiologischer und Psychologische variablen beigestuften Leistungsanforderungen im Rhamen des Konzentra- tionleistung-Tests. Z Psychol 1977;185:347–413.

[36] Tanaka Y, Yamaoka K. Blink activity and task difficulty. Percept Mot Skills 1993;77:55–66.

[37] Barbato G, De Padova V, Paolillo AR, Arpaia L, Russo E, Ficca G. Increasedspontaneous eye blink rate following prolonged wakefulness. Physiol Behav2007;90:151–4.

[38] Barbato G, Ficca G, Muscettola G, Fichele M, Beatrice M, Rinaldi F. Diurnal variationin spontaneous eye-blink rate. Psychiatry Res 2000;93:145–51.

[39] Volkow ND, Wang GJ, Telang F, Fowler JS, Logan J, Wong C, et al. Sleep deprivationdecreases binding of [11 C]raclopride to dopamine D2/D3 receptors in the humanbrain. J Neurosci 2008;28:8454–61.

[40] Volkow ND, Wang GJ, Fowler JS, Logan J, Schlyer D, Hitzemann R, et al. Imagingendogenous dopamine competition with [11 C]raclopride in the human brain.Synapse 1994;16:255–62.

[41] Roger D, Morris J. The internal structure of the EPQ scales. Pers Individ Differ1991;12:759–64.

[42] Jorm AF. Sex differences in neuroticism: a quantitative synthesis of publishedresearch. Australas Psychiatry 1987;21:501–6.

[43] Terman LM, Tyler LE. Psychological sex differences. In: Carmichael L, editor.Manual of child psychology. New York: Wiley; 1954.

[44] Lynn R. Two personality characteristics related to academic achievement. Br J EducPsychol 1959;29:213–6.

[45] Guttman M. A note on MMPI age and sex differences in extraversion andneuroticism in a Canadian sample. Br J Soc Clin Psychol 1966;5:128–9.

[46] Eysenck SB, Eysenck HJ. Scores on three personality variables as a function of age,sex and social class. Br J Soc Clin Psychol 1969;8:69–76.

[47] Eysenck HJ, Eysenck SBG. Psychoticism as a dimension of personality London.Hodder and Stoughton; 1976.

[48] Bentivoglio AR, Bressman SB, Cassetta E, Carretta D, Tonali P, Albanese A. Analysisof blink rate patterns in normal subjects. Mov Disord 1997;12:1028–34.

[49] Matthews G, Gilliland K. The personality theories of H. J. Eysenck and J. A. Gray: acomparative review. Pers Individ Differ 1999;26:583–626.

[50] Karson CN. Physiology of normal and abnormal blinking. Adv Neurol 1988;49:25–37.

[51] Taylor J, Elsworth J, Lawrence M, Sladek J. Spontaneous blink rates correlate withdopamine levels in the caudate nucleus of MPTP-treated monkeys. Exp Neurol1999;158:214–20.

[52] Haas BW, Constable RT, Canli T. Stop the sadness: Neuroticism is associated withsustained medial prefrontal cortex response to emotional facial expressions.Neuroimage 2008;42:385–92.

[53] Wright CI, Williams D, Feczko E, Barrett LF, Dickerson BC, Schwartz CE, et al.Neuroanatomical correlates of extraversion and neuroticism. Cereb Cortex2006;16:1809–19.

[54] Deckersbach T, Miller KK, Klibanski A, Fischman A, Dougherty DD, Blais MA, et al.Regional cerebral brain metabolism correlates of neuroticism and extraversion.Depress Anxiety 2006;23:133–8.

[55] Eisenberger NI, Lieberman MD, Satpute AB. Personality from a controlledprocessing perspective: an fMRI study of neuroticism, extraversion, and self-consciousness. Cogn Affect Behav Neurosci 2005;5:169–81.

[56] Krueger RF. The structure of common mental disorders. Arch Gen Psychiatry1999;56:921–6.

[57] Griffith J, Zinbarg R, Craske M, Mineka S, Rose R, Waters A, et al. Neuroticism as acommon dimension in the internalizing disorders. Psychol Med 2010;40:1125–36.

[58] Jylha P, Isometsa E. The relationship of neuroticism and extraversion to symptomsof anxiety and depression in the general population. Depress Anxiety 2006;23:281–9.

[59] Clark LA, Watson D, Mineka S. Temperament, personality, and the mood andanxiety disorders. J Abnorm Psychol 1994;103:103–16.

[60] Bruhl AB, Viebke MC, Baumgartner T, Kaffenberger T, Herwig U. Neural correlatesof personality dimensions and affective measures during the anticipation ofemotional stimuli. Brain Imaging Behav 2011;5:86–96.

336 G. Barbato et al. / Physiology & Behavior 105 (2012) 332–336

[61] Kammeier ML, Hoffmann H, Loper RG. Personality characteristics of alcoholics ascollege freshmen and at time of treatment. Q J Stud Alcohol 1973;34:390–9.

[62] Mullan M, Gurling H, Oppenheim B, Murray R. The relationship betweenalcoholism and neurosis: evidence from a twin study. Br J Psychiatry 1986;148:435–41.

[63] Sandahl C, Lindberg S, Bergman H. The relation between drinking habits andneuroticism and weak ego among male and female alcoholic patients. ActaPsychiatr Scand 1987;75:500–8.

[64] Shaw G, Waller S, McDougall S, MacGarvie J, Dunn G. Alcoholism: a follow-upstudy of participants in an alcohol treatment programme. Br J Psychiatry1990;157:190–6.

[65] Bottlender M, Soyka M. Impact of different personality dimensions (NEO Five-Factor Inventory) on the outcome of alcohol-dependent patients 6 and 12 monthsafter treatment. Psychiatry Res 2005;136:61–7.