Chronobiology International, 2015; 32(2): 235–241 ! Informa Healthcare USA, Inc. ISSN: 0742-0528 print / 1525-6073 online DOI: 10.3109/07420528.2014.965313
ORIGINAL ARTICLE
Circadian preference and trait impulsivity, sensation-seeking and response inhibition in healthy young adults Jee In Kang1,2, Chun Il Park1,2, Sung-yun Sohn1,2, Hae Won Kim1,2, Kee Namkoong1,2, and Se Joo Kim1,2 1
Department of Psychiatry, Yonsei University College of Medicine, Seoul, Republic of Korea and 2Institute of Behavioral Science in Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea
Circadian preference has been considered related with impulsivity. The purpose of the present study was to evaluate the relationship between circadian typology and impulsivity measured by the Barratt Impulsivity Scale (BIS), sensation-seeking measured by the Sensation Seeking Scale - Form V (SSS-V) and response inhibition elicited by the GO/NO-GO paradigm. A total of 503 Korean healthy college students (288 males and 215 females) completed the Composite Scale of Morningness (CSM) for circadian typology and the BIS and SSS-V for impulsivity and risk taking, respectively. A subset of 142 subjects additionally performed the computerized GO/NO-GO task for motor response inhibition. A significant association was found between the circadian typology of the CSM and impulsivity of the BIS and disinhibition of SSS-V. In addition, there was a difference in trend level between the circadian typology and response inhibition elicited by the GO/NO-GO test. Regarding circadian preference, evening types were significantly associated with higher impulsivity on the BIS, disinhibition on the SSS-V and lower rate of successful inhibition on the GO/NO-GO task compared to morning types. The present results showed significant relationships between circadian preference and impulsivity and sensation-seeking personality traits. In particular, our findings suggest that high impulsivity, disinhibition and impaired response inhibition are more related to evening types. Circadian preference might be associated with psychiatric problems interacting with some aspects of personality traits such as inhibitory control. Keywords: Circadian preference, disinhibition, evening type, impulsivity, response inhibition, sensation-seeking
INTRODUCTION
daily activities (Adan et al., 2012). The circadian preference is thought to follow a normal distribution and individuals can be generally classified into morning, intermediate and evening types. One extreme end of the continuum are the morning types who prefer to wake up early in the morning and find it difficult to remain awake beyond their usual bedtime. In contrast, the other extreme are the evening types who prefer to fall asleep late and have trouble waking up in the morning. Over the last two decades, there has been increased interest in the relationships between the circadian preference and personality dimensions (Adan et al., 2012). In Cloninger’s temperaments, evening type was associated with higher novelty seeking (Adan et al., 2010a; Caci et al., 2004). In addition, morning type subjects have significantly higher conscientiousness among the Big Five personality domains (i.e. extraversion,
Circadian rhythms refer to cyclic fluctuations in many aspects of fundamental physiological functions which play a key role in determining human complex behaviors as well as daily rhythms including sleep regulation. Interest in the associations between circadian rhythms and human neuropsychiatric variables including personality traits and psychiatric vulnerabilities has increased (Hasler & Clark, 2013; Santhi et al., 2007; Schmidt et al., 2007). Although the disruption of circadian rhythms is recognized as an important feature of numerous psychiatric disorders, the exact mechanisms of this process are poorly understood (Wulff et al., 2010). A well-known individual difference in circadian rhythms is circadian preference which is expressed over favorite periods of diurnal activities including timing of sleep and wakefulness and working hours in
Submitted May 2, 2014, Returned for revision August 22, 2014, Accepted September 8, 2014
Correspondence: Professor Se Joo Kim, Department of Psychiatry, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea. Tel: +82-2-2228-1620. Fax: +82-2-313-0891. E-mail: [email protected]
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agreeableness, conscientiousness, neuroticism and openness) than evening types (Randler et al., 2014; Tonetti et al., 2009). Recent research of the Alternative Five Factor Model (AFFM) with a strong biological basis of personality showed that morning types had significant higher scores in Activity dimension than evening and intermediate types (Muro et al., 2009, 2011). These previous reports support that prominent inter-individual variations in the circadian timing system may be linked to differences in the personality dimensions, poor lifestyle choices and vulnerabilities to mental illnesses (Adan et al., 2012). Impulsivity is one of the most widely studied personality dimension in the research on the role of personality traits in psychiatric disorders such as alcohol use disorders (Lejuez et al., 2010) and affective disorders (Johnson et al., 2013). Impulsivity is conceptualized as a predisposition toward rapid, unplanned and unexpected reactions to stimuli with diminished regard to negative consequences (Moeller et al., 2001). High impulsivity is a critical factor contributing to enhanced vulnerability to psychiatric disorders (Swann et al., 2008; VerdejoGarcia et al., 2008) as well as a core feature of various psychiatric illnesses including bipolar disorders (Moeller et al., 2001; Swann et al., 2003). Several reports have suggested relationships between circadian preference and impulsivity. Morning type subjects showed lower scores in dysfunctional impulsivity related to psychoticism and poor behavioral inhibition than evening types, which reflects a protective role of morning type against psychiatric illnesses such as impulse control disorders (Adan et al., 2010b). Additionally, according to a review paper (Schlarb et al., 2014), evening type was associated with elevated vulnerability toward aggression and antisocial behavior in children and adolescents. A research on the AFFM personality and circadian typology showed that evening type women had a significantly higher score on Aggression-Hostility and Impulsive SensationSeeking than morning type women (Muro et al., 2011). Sensation-seeking, defined as a strong need for varied, novel and stimulating experiences and willingness to take risks for the sake of such experiences (Zuckerman et al., 1972), is another personality trait related to impulsivity (Zuckerman et al., 1993). A recent study in which major personality dimensions, impulsivity and sensation-seeking were considered together, showed that impulsivity and sensation-seeking traits were significantly associated with evening type and furthermore, no significant direct effects of the Big Five personality traits were detected once the effects of impulsivity and sensation-seeking were considered (Russo et al., 2012). Human behaviors such as lifestyle choice and biological vulnerability to mental illnesses may be linked to the relationship between impulsivity/sensation-seeking traits and circadian rhythm that are influenced by sleeping and waking cycles in daily activities. Thus, exploring the association between circadian preference and impulsivity and sensation-seeking traits may be
helpful in understanding human behaviors and psychiatric disorders. The present study aimed to extend and clarify the literature on circadian rhythms and impulsivity and sensation-seeking in healthy young adults and cultural difference. We evaluated the relationship between circadian typology and impulsivity measured by Barratt Impulsivity Scale (BIS), sensation-seeking measured by the Sensation-Seeking Scale - Form V (SSS-V), and response inhibition elicited by the GO/NO-GO paradigm. We hypothesized the evening type would be associated with high impulsivity, sensation-seeking traits and deficit of response inhibition.
MATERIALS AND METHODS Subjects A total of 552 healthy Korean college student volunteers (316 males and 236 females) were recruited through advertisements for the study. Subjects with any neurological and current or lifetime Axis I psychiatric disorders according to the DSM-IV (American Psychiatric Association, 1994) criteria were excluded. The Structured Clinical Interview for the DSM-IV (SCID) (First et al., 1997) was assessed by two trained psychiatrists (S.J. KIM and J.I. KANG). In addition, subjects with a family history of mental disorders in first-degree relatives were excluded using the family history method by the two psychiatrists. The study protocol was approved by the Institutional Review Board at Severance Hospital of Yonsei University Health System and every subject gave written informed consent before participating in the study. A subset of subjects was excluded from analysis due to unanswered responses on the questionnaires and cases with outliers identified as an extreme value in the SPSS were also excluded. The outliers were identified (±3 standard deviations (SD) away from the mean) and removed from the data for the following variables: subscale and total scores of the BIS and the SSS-V, and the performance of the GO/NO-GO task. In the final analysis, 503 subjects with complete data sets (288 males and 215 females) were included. The mean age of the final sample was 22.55 years (SD ¼ 2.79 years) for males and 22.06 years (SD ¼ 3.43 years) for females. All participants were ethnic Koreans. Among the present sample group, a more homogenous subset of 150 subjects performed additional computerized GO/NO-GO task. The subset sample consisted of students enrolled from the same college assuming similar cognitive function and was recruited during the latter half of the study period. The final data of the GO/ NO-GO test were analyzed for 142 subjects (73 males and 69 females) after removing outliers. Measures Composite Scale of Morningness The circadian typology was measured using the Composite Scale of Morningness (CSM) (Smith et al., Chronobiology International
Circadian preference and impaired inhibition 1989). The CSM is a widely used scale with 13-items, which have high reliability and validity for measuring circadian preference (Di Milia et al., 2013). Korean version of the CSM used in the present study has been validated previously in the Korean population and proven to have acceptable psychometric properties (Ahn et al., 2008; Yoon et al., 1997). Higher CSM scores reflect higher morningness. We considered the 20th and 80th percentiles for the present subjects as the cutoff criteria for morning and evening typologies (Prat & Adan, 2013). Cutoff points corresponding to the 20th and 80th percentiles in our sample were 28 and 38, respectively, thus subjects scoring 27 points were categorized as evening types, between 28 and 37 as intermediate types and 38 as morning types. The internal consistency of the CSM for the present sample was 0.82.
Korean modified Barratt Impulsivity Scale 11th revision The Korean modified Barratt Impulsivity Scale 11th revision (K-BIS-23) (Lee, 2001; Patton et al., 1995) was applied to assess trait impulsivity. The original survey consists of 30 self-report questions to measure the personality/behavioral construct of impulsivity (Barratt, 2000). The Korean version of BIS-11 used in this study consists of 23 items excluding 7 items showing low validity in the Korean population (Lee, 2001). All items are measured on a 4-point Likert scale with 4 generally indicating the most impulsive response (rarely/never ¼ 1, occasionally ¼ 2, often ¼ 3, almost always/always ¼ 4). The questionnaire measures three factors of nonplanning, motor and attention impulsivity; higher scores indicate higher trait impulsivity. Sensation Seeking Scale Form V of the Sensation Seeking Scale (SSS-V), a 40-item forced-choice questionnaire, was used to assess the sensation-seeking traits (Zuckerman, 1990). The SSS-V measures four subdomains, boredom susceptibility, disinhibition, experience-seeking and thrill/adventureseeking. Each subdomain consisted of 10 questions. Boredom susceptibility indicates a tendency to dislike routine activities, boring people and suggests a restless reaction to a lack of stimulus variety. Disinhibition reflects impaired control of a social hedonistic orientation with the pursuit of a sensation such as drinking or sex. Experience-seeking indicates a desire to seek new experiences through the senses and the mind. Thrill/adventure-seeking reflects a desire to engage in certain types of risky physical activities. For each dichotomous choice, a score of 1 was assigned if the sensation-seeking response was chosen and the total scores represented the number of sensation-seeking responses. GO/NO-GO test To measure motor response inhibition, the computerized GO/NO-GO test was performed. The GO/NO-GO !
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test is a direct measurement of inhibitory control assessing the process related to the selective response inhibition in a faster variant of the classical GO/NO-GO paradigm (Penades et al., 2007). The task requires selection of either a response, indicated by a go signal, or a no response, indicated by a no-go signal. Subjects have to respond to go signals (airplanes) appearing on the center of the screen but not to no-go signals (bombs). In 30% of the trials, the bombs appear on the screen and subjects have to inhibit their motor response. Interstimulus-interval (ISI) was 1000 ms, including stimulus duration of 200 ms followed by a blank screen for 800 ms. The task was administered in 2 blocks of 90 practice and 180 testing trials (126 go trials and 54 no-go trials). The stimuli were presented in randomized order and a task length was during 4 min and 30 sec. The stimulus presentation was administered on a laptop (Window XP) with 14-inch LCD screen. The dependent variables of the inhibitory no-go-process were the percentage of successful inhibition trials (Pi %) and the hit reaction time (ms). All subjects performed the task in the afternoon (12:30 pm to 5:00 pm) to control the impact of potential time-of-day fluctuations on performance (Schmidt et al., 2007).
Statistical analyses All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS Inc., Chicago, IL, USA) version 20. The normal distribution of the data was assessed using histograms and skewness and kurtosis statistics by SPSS. The data were considered within the limits of a normal distribution if the calculated z-scores (dividend of the skewness and kurtosis statistics and their respective standard errors) did not exceed ±2.0 (Ghasemi & Zahediasl, 2012; Kim, 2013). Demographics variables between genders were compared using t-tests or the chi-square test. The reliability of the applied scales was assessed using Cronbach’s coefficient. Multivariate analysis of variance (MANOVA) and post-hoc pairwise comparisons using the Least Significant Difference (LSD) test were conducted to compare the impulsivity and sensationseeking of the K-BIS-23 and the SSS-V among the 3 circadian groups of morning, intermediate and evening types. In the MANOVA, subscale scores of the K-BIS-23 and the SSS-V were the dependent variables and the types of circadian preference and gender were the fixed factors. To estimate the effect size in each dependent variable, the partial eta-squared values (p2 ) were calculated, where a value of 0.01 is small, 0.04 is moderate and 0.1 is large (Huberty, 2002). In addition, effect size for post-hoc group comparisons was calculated based on Cohen’s d (Cohen, 1988). For the GO/NO-GO test in a subset of 142 subjects, the Pi % and the reaction time to go trials was compared among circadian groups using MANOVA. The significance level was set at p50.05. All tests were two-tailed.
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RESULTS The present sample consisted of 97 morning (51 males, 46 females), 300 intermediate (186 males, 114 females) and 106 evening (51 males, 55 females) types. The distribution of the 3 chronotypes between genders showed a significant difference ( 2 ¼ 7.25, df ¼ 2, p ¼ 0.027), with a slightly higher proportion of morning type in females than males (Table 1). The histograms of the variables indicated normal distributions. Skewness and kurtosis were 0.071 (z ¼ 0.66) and 0.35 (z ¼ 1.63) for the K-BIS-23 and 0.20 (z ¼ 1.86) and 0.21 (z ¼ 0.98) for the SSS-V, respectively. Because the calculated z-scores did not exceed ± 2.0, we used parametric methods in subsequent analyses. The mean values for the non-planning, motor and attention subscales and total scores of the K-BIS-23, the boredom susceptibility, disinhibition, experience-seeking and thrill/adventure-seeking subscales and total scores of the SSS-V are presented in Table 1. In the MANOVA with two fixed factors (gender and circadian groups), there was no interaction effect between gender and circadian typology for trait impulsivity and sensation-seeking (Wilks’ Lambda F ¼ 1.60, df ¼ 14, 982, p ¼ 0.073). MANOVA showed significant differences between circadian groups in trait impulsivity and sensation-seeking of the K-BIS-23 and SSS-V (Wilks’ Lambda F ¼ 3.11, df ¼ 14, 982, p50.001, p2 ¼ 0.042; Table 2). Post-hoc LSD analyses indicated the evening type subjects had significantly higher impulsivity scores
TABLE 1. Demographics variables and K-BIS-23 and SSS-V subscale scores according to gender. Total sample (n ¼ 503) Age (years) Education (years) Circadian typology Evening type Intermediate type Morning type K-BIS-23 Total score Non-plan Motor Attention SSS-V Total score Boredom susceptibility Disinhibition Experience seeking Thrill Seeking Subsequent sample (n ¼ 142) GO/NO-GO task Pi (%) Hit reaction time (ms)
Male (n ¼ 288)
Female (n ¼ 215)
22.55 ± 2.79 14.21 ± 1.48
22.06 ± 3.43 14.45 ± 1.63
51 (17.7%) 186 (64.6%) 51 (17.7%)
46 (21.4%) 114 (53.0%) 55 (25.6%)
p value 0.081 0.088
0.027
49.52 ± 6.94 20.78 ± 3.22 14.59 ± 3.10 14.15 ± 2.28
50.25 ± 6.74 20.87 ± 3.16 14.94 ± 3.16 14.44 ± 2.24
0.24 0.76 0.20 0.16
19.62 ± 5.80 2.37 ± 1.71 5.18 ± 2.16 5.46 ± 2.09 6.61 ± 2.58
18.52 ± 5.67 2.07 ± 1.66 4.79 ± 2.22 5.48 ± 2.09 6.17 ± 2.68
0.034 0.050 0.053 0.91 0.061
Male (n ¼ 73)
Female (n ¼ 69)
87.42 ± 9.68 279.95 ± 25.10
90.53 ± 9.21 296.41 ± 29.53
0.052 50.001
Data are means ± standard deviation (SD) values. All tests are twotailed. Pi: the percentage of successful inhibition trials
on all subscales and total scores of the K-BIS-23 than morning (all p50.005) and intermediate types (all p50.05). Among the subscales of the SSS-V, there was a significant association between disinhibition subscale and circadian typology (p ¼ 0.038) and subsequent posthoc comparisons showed that morning type subjects had a significantly lower level of disinhibition than evening (p ¼ 0.023) and intermediate types (p ¼ 0.012). The mean scale values and the results from group comparisons among chronotypes are presented in Table 2. In a subset of 142 subjects, significant group differences were observed between circadian groups and GO/ NO-GO performance (F ¼ 3.03, df ¼ 4, 276, p ¼ 0.018; Table 3). Evening type subjects had a lower successful inhibition at trend level (p ¼ 0.058) than morning (Cohen’s d ¼ 0.58) and intermediate types (Cohen’s d ¼ 0.42). In addition, morning types had slower reaction times than evening (Cohen’s d ¼ 0.51) and intermediate (Cohen’s d ¼ 0.46) types (Table 3).
DISCUSSION The present study examined the relationship between circadian preference and impulsivity, sensation-seeking and response inhibition in healthy college students. The results revealed that evening types are related to high impulsivity trait on the BIS, disinhibition measured by the SSS-V and poor response inhibition elicited by the GO/NO-GO paradigm. The present results for Korean population are in line with previous studies in Spanish populations (Muro et al., 2011, 2012). Consistent with these findings, a recent Italian study suggested associations of personality traits and circadian preference are explained by the effects of impulsivity and sensationseeking rather than the Big Five personality traits (Russo et al., 2012). These findings suggest that circadian preference has a modulatory role in certain personality dimensions such as impulsivity and contributes to lifestyle and psychiatric vulnerabilities. While evening types were related to high impulsivity traits based on the BIS as shown in the previous findings, several different aspects of sensation-seeking traits were observed among studies. In the present study, a significant difference among chronotypes was observed only for the disinhibition subscale of the SSSV. Tonetti et al. (2010) reported that evening types scored higher on all subscales of the SSS-V, whereas Prat & Adan (2013) showed that evening types scored higher on the two subscales of disinhibition and boredom susceptibility of the SSS-V than the morning types. Another study with adolescents showed that evening types were significantly related to three subscales except for thrill/adventure-seeking among the SSS-V subscales (Muro et al., 2012). These differential patterns of relationships between the SSS-V subscales and chronotypes may be due to several reasons including different sample sizes, the used measures of circadian preference (Morningness-Eveningness Questionnaire (MEQ) versus Chronobiology International
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TABLE 2. K-BIS-23 and SSS-V subscale scores according to chronotype based on MANOVA (n ¼ 503). Evening type; E Intermediate; I Morning type; M (n ¼ 97) (n ¼ 300) (n ¼ 106) p Value K-BIS-23_Total score K-BIS_Non-planning K-BIS_Motor K-BIS_Attention SSS_Total score SSS_Boredom Susceptibility SSS_Disinhibition SSS_Experience Seeking SSS_Thrill Seeking
52.65 ± 6.38 22.00 ± 2.84 15.80 ± 3.23 14.85 ± 2.33 19.09 ± 5.62 2.36 ± 1.69 5.21 ± 2.24 5.31 ± 2.11 6.22 ± 2.49
49.64 ± 6.71 20.73 ± 3.14 14.60 ± 3.05 14.31 ± 2.19 19.23 ± 5.75 2.28 ± 1.72 5.13 ± 2.13 5.49 ± 2.09 6.33 ± 2.63
47.80 ± 6.93 19.98 ± 3.36 14.17 ± 2.97 13.65 ± 2.28 18.97 ± 6.00 2.02 ± 1.60 4.51 ± 2.23 5.58 ± 2.08 6.87 ± 2.72
Cohen’s d Post-hoc comparisons E4M E4I I4M
p2
50.001 0.052 50.001 0.041 50.001 0.031 0.001 0.028 0.962 50.001 0.352 0.005 0.038 0.014 0.573 0.002 0.099 0.008
E4I4M E4I4M E4I4M E4I4M
0.73 0.65 0.53 0.52
0.46 0.42 0.38 0.24
0.27 0.23 0.14 0.29
E4M, I4M
0.31
0.03
0.28
Data are means ± standard deviation (SD) values. All tests are two-tailed. MANOVA Wilks’ Lambda F ¼ 3.11, df ¼ 14, 982, p50.001
TABLE 3. Differences of the percentage of successful trials and mean reaction time of the GO/NO-GO task according to chronotype (n ¼ 142).
GO/NO-GO task
Evening type; E (n ¼ 26)
Intermediate; I (n ¼ 83)
Morning type; M (n ¼ 33)
Pi (%) Hit reaction time
85.11 ± 10.94 283.27 ± 23.25
89.36 ± 9.20 284.80 ± 23.70
90.85 ± 8.65 299.57 ± 39.07
Cohen’s d
p Value
p2
Post-hoc comparisons
E5M
E5I
I5M
0.058 0.026
0.040 0.051
E5M, E5I E5M, I5M
0.58 0.51
0.42 0.07
0.17 0.46
Data are means ± standard deviation (SD) values. All tests are two-tailed. Pi: the percentage of successful inhibition trials. MANOVA Wilks’ Lambda F ¼ 3.03, df ¼ 4, 276, p ¼ 0.018
CSQ), age differences and the cutoff classification of chronotypes. Nevertheless, the most consistent finding across studies using the SSS-V was the relationship between the disinhibition subscale and the evening types, which was also shown to be significant in the present study. The disinhibition subscale of the SSS-V is more strongly correlated than other subscales to behavioral disinhibition such as alcohol drinking behaviors (Hittner & Swickert, 2006). A core personality trait related to circadian rhythm may be impulsivity related to behavioral inhibition rather than seeking novel stimuli itself. Although impulsivity and sensation-seeking traits may share some personality features and influence each other, they have conceptually and empirically distinct characteristics. Impulsivity is a multifaceted construct consisting of impulsive decision and a lack of inhibitory control (Evenden, 1999). Sensation-seeking, in contrast, refers to the tendency to seek out novel and highly stimulating experiences and the willingness to take risks to attain them (Zuckerman, 1972) which appears to be more related to behavioral approach systems (Poythress et al., 2008). The disinhibition subscale that is typically defined in terms of behavioral disinhibition or undercontrol may reflect a conceptual overlap between the two constructs. A previous study showed that eveningness was associated with impulsivity but not venturesomeness (Caci et al., 2005). Additionally, evening types were related to dysfunctional impulsivity but not functional impulsivity such as extraversion in Dickman’s !
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model (Adan et al., 2010b; Dickman, 1990). Collectively, evening types would rather be involved in impulsivity traits related to behavioral inhibition than seeking novelty or personal gain. Although no single personality dimension is likely associated with psychiatric vulnerability related to circadian rhythms, a core personality trait related to circadian rhythm may be impulsivity of inhibitory control. This can be supported by the present results of GO/ NO-GO paradigm in which evening type subjects had lower level of successful response inhibition (marginal significance, p ¼ 0.058) and morning types had slower reaction times. Deficit of response inhibition is particularly interesting because it is considered a vulnerable marker of bipolar disorders (Roberts et al., 2013) and substance use disorders (Nigg et al., 2006). Impaired response inhibition may mediate dysregulation of circadian rhythms into behavioral disinhibition problems and psychiatric disorders. The present findings need further investigation because they suggest a possible pathophysiological approach to impaired inhibition that may be accessible by circadian interventions such as morning sunlight exposure. The present study had several limitations. First, the classification of circadian preference in the present data relied on self-reported measures of chronotypes. Further replication studies using objective assessments of sleepwake cycles would strengthen the clinical implications of chronotypes on impulsivity traits. Second, the internal consistency of the K-BIS-23 subscales in the
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present sample was not high (Cronbach’s a coefficients: 0.52, 0.70, and 0.46 for non-planning, motor and attention subscales, respectively). As poor fit to the confirmatory model of the factor structures have also been argued in other studies using BIS-11 for other populations (Reise et al., 2013), this may be one limitation and should be interpreted cautiously. Third, the present study with non-experimental cross-sectional design leaves some unanswered questions regarding the links and the underlying mechanisms between chronotypes, and impulsivity and sensation-seeking traits. Finally, our results obtained from healthy volunteers may be difficult to generalize to clinical populations. Future research including clinical samples is needed to reveal the mediating role of chronotypes between dispositional impulsive factors such as inhibitory control and mental illnesses related to impulsivity. Overall, the present results showed significant relationships between circadian preference and the personality traits of impulsivity and sensation-seeking. In particular, high impulsivity, disinhibition of sensationseeking, and impaired response inhibition were related to evening types. Our findings suggest that circadian rhythms might be associated with psychiatric problems interacting with personality traits such as impulsivity and the elevated vulnerability toward impulsivity in evening type subjects supports the need for developing early circadian intervention programs that warn against the consequences of disrupted circadian rhythm and promote healthy sleep hygiene and lifestyle regularity in daily activities. Further clinical and neurobiological studies are needed to demonstrate causality of the effects in question.
DECLARATION OF INTEREST This work was supported by a new faculty research seed money grant of Yonsei University College of Medicine for 2014-32-0009. The authors report no conflict of interest.
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Circadian preference and impaired inhibition Randler C, Baumanna V, Horzumb M. (2014). Morningness– eveningness, Big Five and the BIS/BAS inventory. Pers Individual Differences. 66:64–7. Reise SP, Moore TM, Sabb FW, et al. (2013). The Barratt Impulsiveness Scale-11: Reassessment of its structure in a community sample. Psychol assess. 25:631–42. Roberts G, Green MJ, Breakspear M, et al. (2013). Reduced inferior frontal gyrus activation during response inhibition to emotional stimuli in youth at high risk of bipolar disorder. Biol Psychiatry 74:55–61. Russo PM, Leone L, Penolazzi B, Natale V. (2012). Circadian preference and the big five: The role of impulsivity and sensation seeking. Chronobiol Int. 29:1121–6. Santhi N, Horowitz TS, Duffy JF, Czeisler CA. (2007). Acute sleep deprivation and circadian misalignment associated with transition onto the first night of work impairs visual selective attention. PLoS One. 2:e1233. Schlarb AA, Sopp R, Ambiel D, Grunwald J. (2014). Chronotyperelated differences in childhood and adolescent aggression and antisocial behavior-a review of the literature. Chronobiol Int. 31:1–16. Schmidt C, Collette F, Cajochen C, Peigneux P. (2007). A time to think: Circadian rhythms in human cognition. Cognit Neuropsychol. 24:755–89. Smith CS, Reilly C, Midkiff K. (1989). Evaluation of three circadian rhythm questionnaires with suggestions for an improved measure of morningness. J Appl Psychol. 74:728–38. Swann AC, Pazzaglia P, Nicholls A, et al. (2003). Impulsivity and phase of illness in bipolar disorder. J Affect Disord. 73:105–11.
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Swann AC, Steinberg JL, Lijffijt M, Moeller FG. (2008). Impulsivity: Differential relationship to depression and mania in bipolar disorder. J Affect Disord. 106:241–8. Tonetti L, Adan A, Caci H, et al. (2010). Morningness-eveningness preference and sensation seeking. Eur Psychiatry 25:111–15. Tonetti L, Fabbri M, Natale V. (2009). Relationship between circadian typology and big five personality domains. Chronobiol Int. 26:337–47. Verdejo-Garcia A, Lawrence AJ, Clark L. (2008). Impulsivity as a vulnerability marker for substance-use disorders: Review of findings from high-risk research, problem gamblers and genetic association studies. Neurosci Biobehav Rev. 32:777–810. Wulff K, Gatti S, Wettstein JG, Foster RG. (2010). Sleep and circadian rhythm disruption in psychiatric and neurodegenerative disease. Nat Rev Neurosci. 11:589–99. Yoon JS, Shin SM, Kook SH, Hy L. (1997). A preliminary study on the Korean Translation of Composite Scale (KtCS) to measure morningness–eveningness. J Korean Neuropsychiatr Assoc. 36: 122–30. Zuckerman M, Bone RN, Neary R, et al. (1972). What is the sensation seeker? Personality trait and experience correlates of the Sensation-Seeking Scales. J J Consult Clin Psychol. 39: 308–21. Zuckerman M, Kuhlman DM, Joireman J, et al. (1993). A comparison of three structural models for personality: The big three, the big five, and the alternative five. J Pers Soc Psychol. 65:757–68. Zuckerman M. (1990). The psychophysiology of sensation seeking. J Pers. 58:313–45.
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ORIGINAL ARTICLE
Circadian preference and trait impulsivity, sensation-seeking and response inhibition in healthy young adults Jee In Kang1,2, Chun Il Park1,2, Sung-yun Sohn1,2, Hae Won Kim1,2, Kee Namkoong1,2, and Se Joo Kim1,2 1
Department of Psychiatry, Yonsei University College of Medicine, Seoul, Republic of Korea and 2Institute of Behavioral Science in Medicine, Yonsei University College of Medicine, Seoul, Republic of Korea
Circadian preference has been considered related with impulsivity. The purpose of the present study was to evaluate the relationship between circadian typology and impulsivity measured by the Barratt Impulsivity Scale (BIS), sensation-seeking measured by the Sensation Seeking Scale - Form V (SSS-V) and response inhibition elicited by the GO/NO-GO paradigm. A total of 503 Korean healthy college students (288 males and 215 females) completed the Composite Scale of Morningness (CSM) for circadian typology and the BIS and SSS-V for impulsivity and risk taking, respectively. A subset of 142 subjects additionally performed the computerized GO/NO-GO task for motor response inhibition. A significant association was found between the circadian typology of the CSM and impulsivity of the BIS and disinhibition of SSS-V. In addition, there was a difference in trend level between the circadian typology and response inhibition elicited by the GO/NO-GO test. Regarding circadian preference, evening types were significantly associated with higher impulsivity on the BIS, disinhibition on the SSS-V and lower rate of successful inhibition on the GO/NO-GO task compared to morning types. The present results showed significant relationships between circadian preference and impulsivity and sensation-seeking personality traits. In particular, our findings suggest that high impulsivity, disinhibition and impaired response inhibition are more related to evening types. Circadian preference might be associated with psychiatric problems interacting with some aspects of personality traits such as inhibitory control. Keywords: Circadian preference, disinhibition, evening type, impulsivity, response inhibition, sensation-seeking
INTRODUCTION
daily activities (Adan et al., 2012). The circadian preference is thought to follow a normal distribution and individuals can be generally classified into morning, intermediate and evening types. One extreme end of the continuum are the morning types who prefer to wake up early in the morning and find it difficult to remain awake beyond their usual bedtime. In contrast, the other extreme are the evening types who prefer to fall asleep late and have trouble waking up in the morning. Over the last two decades, there has been increased interest in the relationships between the circadian preference and personality dimensions (Adan et al., 2012). In Cloninger’s temperaments, evening type was associated with higher novelty seeking (Adan et al., 2010a; Caci et al., 2004). In addition, morning type subjects have significantly higher conscientiousness among the Big Five personality domains (i.e. extraversion,
Circadian rhythms refer to cyclic fluctuations in many aspects of fundamental physiological functions which play a key role in determining human complex behaviors as well as daily rhythms including sleep regulation. Interest in the associations between circadian rhythms and human neuropsychiatric variables including personality traits and psychiatric vulnerabilities has increased (Hasler & Clark, 2013; Santhi et al., 2007; Schmidt et al., 2007). Although the disruption of circadian rhythms is recognized as an important feature of numerous psychiatric disorders, the exact mechanisms of this process are poorly understood (Wulff et al., 2010). A well-known individual difference in circadian rhythms is circadian preference which is expressed over favorite periods of diurnal activities including timing of sleep and wakefulness and working hours in
Submitted May 2, 2014, Returned for revision August 22, 2014, Accepted September 8, 2014
Correspondence: Professor Se Joo Kim, Department of Psychiatry, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea. Tel: +82-2-2228-1620. Fax: +82-2-313-0891. E-mail: [email protected]
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agreeableness, conscientiousness, neuroticism and openness) than evening types (Randler et al., 2014; Tonetti et al., 2009). Recent research of the Alternative Five Factor Model (AFFM) with a strong biological basis of personality showed that morning types had significant higher scores in Activity dimension than evening and intermediate types (Muro et al., 2009, 2011). These previous reports support that prominent inter-individual variations in the circadian timing system may be linked to differences in the personality dimensions, poor lifestyle choices and vulnerabilities to mental illnesses (Adan et al., 2012). Impulsivity is one of the most widely studied personality dimension in the research on the role of personality traits in psychiatric disorders such as alcohol use disorders (Lejuez et al., 2010) and affective disorders (Johnson et al., 2013). Impulsivity is conceptualized as a predisposition toward rapid, unplanned and unexpected reactions to stimuli with diminished regard to negative consequences (Moeller et al., 2001). High impulsivity is a critical factor contributing to enhanced vulnerability to psychiatric disorders (Swann et al., 2008; VerdejoGarcia et al., 2008) as well as a core feature of various psychiatric illnesses including bipolar disorders (Moeller et al., 2001; Swann et al., 2003). Several reports have suggested relationships between circadian preference and impulsivity. Morning type subjects showed lower scores in dysfunctional impulsivity related to psychoticism and poor behavioral inhibition than evening types, which reflects a protective role of morning type against psychiatric illnesses such as impulse control disorders (Adan et al., 2010b). Additionally, according to a review paper (Schlarb et al., 2014), evening type was associated with elevated vulnerability toward aggression and antisocial behavior in children and adolescents. A research on the AFFM personality and circadian typology showed that evening type women had a significantly higher score on Aggression-Hostility and Impulsive SensationSeeking than morning type women (Muro et al., 2011). Sensation-seeking, defined as a strong need for varied, novel and stimulating experiences and willingness to take risks for the sake of such experiences (Zuckerman et al., 1972), is another personality trait related to impulsivity (Zuckerman et al., 1993). A recent study in which major personality dimensions, impulsivity and sensation-seeking were considered together, showed that impulsivity and sensation-seeking traits were significantly associated with evening type and furthermore, no significant direct effects of the Big Five personality traits were detected once the effects of impulsivity and sensation-seeking were considered (Russo et al., 2012). Human behaviors such as lifestyle choice and biological vulnerability to mental illnesses may be linked to the relationship between impulsivity/sensation-seeking traits and circadian rhythm that are influenced by sleeping and waking cycles in daily activities. Thus, exploring the association between circadian preference and impulsivity and sensation-seeking traits may be
helpful in understanding human behaviors and psychiatric disorders. The present study aimed to extend and clarify the literature on circadian rhythms and impulsivity and sensation-seeking in healthy young adults and cultural difference. We evaluated the relationship between circadian typology and impulsivity measured by Barratt Impulsivity Scale (BIS), sensation-seeking measured by the Sensation-Seeking Scale - Form V (SSS-V), and response inhibition elicited by the GO/NO-GO paradigm. We hypothesized the evening type would be associated with high impulsivity, sensation-seeking traits and deficit of response inhibition.
MATERIALS AND METHODS Subjects A total of 552 healthy Korean college student volunteers (316 males and 236 females) were recruited through advertisements for the study. Subjects with any neurological and current or lifetime Axis I psychiatric disorders according to the DSM-IV (American Psychiatric Association, 1994) criteria were excluded. The Structured Clinical Interview for the DSM-IV (SCID) (First et al., 1997) was assessed by two trained psychiatrists (S.J. KIM and J.I. KANG). In addition, subjects with a family history of mental disorders in first-degree relatives were excluded using the family history method by the two psychiatrists. The study protocol was approved by the Institutional Review Board at Severance Hospital of Yonsei University Health System and every subject gave written informed consent before participating in the study. A subset of subjects was excluded from analysis due to unanswered responses on the questionnaires and cases with outliers identified as an extreme value in the SPSS were also excluded. The outliers were identified (±3 standard deviations (SD) away from the mean) and removed from the data for the following variables: subscale and total scores of the BIS and the SSS-V, and the performance of the GO/NO-GO task. In the final analysis, 503 subjects with complete data sets (288 males and 215 females) were included. The mean age of the final sample was 22.55 years (SD ¼ 2.79 years) for males and 22.06 years (SD ¼ 3.43 years) for females. All participants were ethnic Koreans. Among the present sample group, a more homogenous subset of 150 subjects performed additional computerized GO/NO-GO task. The subset sample consisted of students enrolled from the same college assuming similar cognitive function and was recruited during the latter half of the study period. The final data of the GO/ NO-GO test were analyzed for 142 subjects (73 males and 69 females) after removing outliers. Measures Composite Scale of Morningness The circadian typology was measured using the Composite Scale of Morningness (CSM) (Smith et al., Chronobiology International
Circadian preference and impaired inhibition 1989). The CSM is a widely used scale with 13-items, which have high reliability and validity for measuring circadian preference (Di Milia et al., 2013). Korean version of the CSM used in the present study has been validated previously in the Korean population and proven to have acceptable psychometric properties (Ahn et al., 2008; Yoon et al., 1997). Higher CSM scores reflect higher morningness. We considered the 20th and 80th percentiles for the present subjects as the cutoff criteria for morning and evening typologies (Prat & Adan, 2013). Cutoff points corresponding to the 20th and 80th percentiles in our sample were 28 and 38, respectively, thus subjects scoring 27 points were categorized as evening types, between 28 and 37 as intermediate types and 38 as morning types. The internal consistency of the CSM for the present sample was 0.82.
Korean modified Barratt Impulsivity Scale 11th revision The Korean modified Barratt Impulsivity Scale 11th revision (K-BIS-23) (Lee, 2001; Patton et al., 1995) was applied to assess trait impulsivity. The original survey consists of 30 self-report questions to measure the personality/behavioral construct of impulsivity (Barratt, 2000). The Korean version of BIS-11 used in this study consists of 23 items excluding 7 items showing low validity in the Korean population (Lee, 2001). All items are measured on a 4-point Likert scale with 4 generally indicating the most impulsive response (rarely/never ¼ 1, occasionally ¼ 2, often ¼ 3, almost always/always ¼ 4). The questionnaire measures three factors of nonplanning, motor and attention impulsivity; higher scores indicate higher trait impulsivity. Sensation Seeking Scale Form V of the Sensation Seeking Scale (SSS-V), a 40-item forced-choice questionnaire, was used to assess the sensation-seeking traits (Zuckerman, 1990). The SSS-V measures four subdomains, boredom susceptibility, disinhibition, experience-seeking and thrill/adventureseeking. Each subdomain consisted of 10 questions. Boredom susceptibility indicates a tendency to dislike routine activities, boring people and suggests a restless reaction to a lack of stimulus variety. Disinhibition reflects impaired control of a social hedonistic orientation with the pursuit of a sensation such as drinking or sex. Experience-seeking indicates a desire to seek new experiences through the senses and the mind. Thrill/adventure-seeking reflects a desire to engage in certain types of risky physical activities. For each dichotomous choice, a score of 1 was assigned if the sensation-seeking response was chosen and the total scores represented the number of sensation-seeking responses. GO/NO-GO test To measure motor response inhibition, the computerized GO/NO-GO test was performed. The GO/NO-GO !
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test is a direct measurement of inhibitory control assessing the process related to the selective response inhibition in a faster variant of the classical GO/NO-GO paradigm (Penades et al., 2007). The task requires selection of either a response, indicated by a go signal, or a no response, indicated by a no-go signal. Subjects have to respond to go signals (airplanes) appearing on the center of the screen but not to no-go signals (bombs). In 30% of the trials, the bombs appear on the screen and subjects have to inhibit their motor response. Interstimulus-interval (ISI) was 1000 ms, including stimulus duration of 200 ms followed by a blank screen for 800 ms. The task was administered in 2 blocks of 90 practice and 180 testing trials (126 go trials and 54 no-go trials). The stimuli were presented in randomized order and a task length was during 4 min and 30 sec. The stimulus presentation was administered on a laptop (Window XP) with 14-inch LCD screen. The dependent variables of the inhibitory no-go-process were the percentage of successful inhibition trials (Pi %) and the hit reaction time (ms). All subjects performed the task in the afternoon (12:30 pm to 5:00 pm) to control the impact of potential time-of-day fluctuations on performance (Schmidt et al., 2007).
Statistical analyses All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS Inc., Chicago, IL, USA) version 20. The normal distribution of the data was assessed using histograms and skewness and kurtosis statistics by SPSS. The data were considered within the limits of a normal distribution if the calculated z-scores (dividend of the skewness and kurtosis statistics and their respective standard errors) did not exceed ±2.0 (Ghasemi & Zahediasl, 2012; Kim, 2013). Demographics variables between genders were compared using t-tests or the chi-square test. The reliability of the applied scales was assessed using Cronbach’s coefficient. Multivariate analysis of variance (MANOVA) and post-hoc pairwise comparisons using the Least Significant Difference (LSD) test were conducted to compare the impulsivity and sensationseeking of the K-BIS-23 and the SSS-V among the 3 circadian groups of morning, intermediate and evening types. In the MANOVA, subscale scores of the K-BIS-23 and the SSS-V were the dependent variables and the types of circadian preference and gender were the fixed factors. To estimate the effect size in each dependent variable, the partial eta-squared values (p2 ) were calculated, where a value of 0.01 is small, 0.04 is moderate and 0.1 is large (Huberty, 2002). In addition, effect size for post-hoc group comparisons was calculated based on Cohen’s d (Cohen, 1988). For the GO/NO-GO test in a subset of 142 subjects, the Pi % and the reaction time to go trials was compared among circadian groups using MANOVA. The significance level was set at p50.05. All tests were two-tailed.
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RESULTS The present sample consisted of 97 morning (51 males, 46 females), 300 intermediate (186 males, 114 females) and 106 evening (51 males, 55 females) types. The distribution of the 3 chronotypes between genders showed a significant difference ( 2 ¼ 7.25, df ¼ 2, p ¼ 0.027), with a slightly higher proportion of morning type in females than males (Table 1). The histograms of the variables indicated normal distributions. Skewness and kurtosis were 0.071 (z ¼ 0.66) and 0.35 (z ¼ 1.63) for the K-BIS-23 and 0.20 (z ¼ 1.86) and 0.21 (z ¼ 0.98) for the SSS-V, respectively. Because the calculated z-scores did not exceed ± 2.0, we used parametric methods in subsequent analyses. The mean values for the non-planning, motor and attention subscales and total scores of the K-BIS-23, the boredom susceptibility, disinhibition, experience-seeking and thrill/adventure-seeking subscales and total scores of the SSS-V are presented in Table 1. In the MANOVA with two fixed factors (gender and circadian groups), there was no interaction effect between gender and circadian typology for trait impulsivity and sensation-seeking (Wilks’ Lambda F ¼ 1.60, df ¼ 14, 982, p ¼ 0.073). MANOVA showed significant differences between circadian groups in trait impulsivity and sensation-seeking of the K-BIS-23 and SSS-V (Wilks’ Lambda F ¼ 3.11, df ¼ 14, 982, p50.001, p2 ¼ 0.042; Table 2). Post-hoc LSD analyses indicated the evening type subjects had significantly higher impulsivity scores
TABLE 1. Demographics variables and K-BIS-23 and SSS-V subscale scores according to gender. Total sample (n ¼ 503) Age (years) Education (years) Circadian typology Evening type Intermediate type Morning type K-BIS-23 Total score Non-plan Motor Attention SSS-V Total score Boredom susceptibility Disinhibition Experience seeking Thrill Seeking Subsequent sample (n ¼ 142) GO/NO-GO task Pi (%) Hit reaction time (ms)
Male (n ¼ 288)
Female (n ¼ 215)
22.55 ± 2.79 14.21 ± 1.48
22.06 ± 3.43 14.45 ± 1.63
51 (17.7%) 186 (64.6%) 51 (17.7%)
46 (21.4%) 114 (53.0%) 55 (25.6%)
p value 0.081 0.088
0.027
49.52 ± 6.94 20.78 ± 3.22 14.59 ± 3.10 14.15 ± 2.28
50.25 ± 6.74 20.87 ± 3.16 14.94 ± 3.16 14.44 ± 2.24
0.24 0.76 0.20 0.16
19.62 ± 5.80 2.37 ± 1.71 5.18 ± 2.16 5.46 ± 2.09 6.61 ± 2.58
18.52 ± 5.67 2.07 ± 1.66 4.79 ± 2.22 5.48 ± 2.09 6.17 ± 2.68
0.034 0.050 0.053 0.91 0.061
Male (n ¼ 73)
Female (n ¼ 69)
87.42 ± 9.68 279.95 ± 25.10
90.53 ± 9.21 296.41 ± 29.53
0.052 50.001
Data are means ± standard deviation (SD) values. All tests are twotailed. Pi: the percentage of successful inhibition trials
on all subscales and total scores of the K-BIS-23 than morning (all p50.005) and intermediate types (all p50.05). Among the subscales of the SSS-V, there was a significant association between disinhibition subscale and circadian typology (p ¼ 0.038) and subsequent posthoc comparisons showed that morning type subjects had a significantly lower level of disinhibition than evening (p ¼ 0.023) and intermediate types (p ¼ 0.012). The mean scale values and the results from group comparisons among chronotypes are presented in Table 2. In a subset of 142 subjects, significant group differences were observed between circadian groups and GO/ NO-GO performance (F ¼ 3.03, df ¼ 4, 276, p ¼ 0.018; Table 3). Evening type subjects had a lower successful inhibition at trend level (p ¼ 0.058) than morning (Cohen’s d ¼ 0.58) and intermediate types (Cohen’s d ¼ 0.42). In addition, morning types had slower reaction times than evening (Cohen’s d ¼ 0.51) and intermediate (Cohen’s d ¼ 0.46) types (Table 3).
DISCUSSION The present study examined the relationship between circadian preference and impulsivity, sensation-seeking and response inhibition in healthy college students. The results revealed that evening types are related to high impulsivity trait on the BIS, disinhibition measured by the SSS-V and poor response inhibition elicited by the GO/NO-GO paradigm. The present results for Korean population are in line with previous studies in Spanish populations (Muro et al., 2011, 2012). Consistent with these findings, a recent Italian study suggested associations of personality traits and circadian preference are explained by the effects of impulsivity and sensationseeking rather than the Big Five personality traits (Russo et al., 2012). These findings suggest that circadian preference has a modulatory role in certain personality dimensions such as impulsivity and contributes to lifestyle and psychiatric vulnerabilities. While evening types were related to high impulsivity traits based on the BIS as shown in the previous findings, several different aspects of sensation-seeking traits were observed among studies. In the present study, a significant difference among chronotypes was observed only for the disinhibition subscale of the SSSV. Tonetti et al. (2010) reported that evening types scored higher on all subscales of the SSS-V, whereas Prat & Adan (2013) showed that evening types scored higher on the two subscales of disinhibition and boredom susceptibility of the SSS-V than the morning types. Another study with adolescents showed that evening types were significantly related to three subscales except for thrill/adventure-seeking among the SSS-V subscales (Muro et al., 2012). These differential patterns of relationships between the SSS-V subscales and chronotypes may be due to several reasons including different sample sizes, the used measures of circadian preference (Morningness-Eveningness Questionnaire (MEQ) versus Chronobiology International
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TABLE 2. K-BIS-23 and SSS-V subscale scores according to chronotype based on MANOVA (n ¼ 503). Evening type; E Intermediate; I Morning type; M (n ¼ 97) (n ¼ 300) (n ¼ 106) p Value K-BIS-23_Total score K-BIS_Non-planning K-BIS_Motor K-BIS_Attention SSS_Total score SSS_Boredom Susceptibility SSS_Disinhibition SSS_Experience Seeking SSS_Thrill Seeking
52.65 ± 6.38 22.00 ± 2.84 15.80 ± 3.23 14.85 ± 2.33 19.09 ± 5.62 2.36 ± 1.69 5.21 ± 2.24 5.31 ± 2.11 6.22 ± 2.49
49.64 ± 6.71 20.73 ± 3.14 14.60 ± 3.05 14.31 ± 2.19 19.23 ± 5.75 2.28 ± 1.72 5.13 ± 2.13 5.49 ± 2.09 6.33 ± 2.63
47.80 ± 6.93 19.98 ± 3.36 14.17 ± 2.97 13.65 ± 2.28 18.97 ± 6.00 2.02 ± 1.60 4.51 ± 2.23 5.58 ± 2.08 6.87 ± 2.72
Cohen’s d Post-hoc comparisons E4M E4I I4M
p2
50.001 0.052 50.001 0.041 50.001 0.031 0.001 0.028 0.962 50.001 0.352 0.005 0.038 0.014 0.573 0.002 0.099 0.008
E4I4M E4I4M E4I4M E4I4M
0.73 0.65 0.53 0.52
0.46 0.42 0.38 0.24
0.27 0.23 0.14 0.29
E4M, I4M
0.31
0.03
0.28
Data are means ± standard deviation (SD) values. All tests are two-tailed. MANOVA Wilks’ Lambda F ¼ 3.11, df ¼ 14, 982, p50.001
TABLE 3. Differences of the percentage of successful trials and mean reaction time of the GO/NO-GO task according to chronotype (n ¼ 142).
GO/NO-GO task
Evening type; E (n ¼ 26)
Intermediate; I (n ¼ 83)
Morning type; M (n ¼ 33)
Pi (%) Hit reaction time
85.11 ± 10.94 283.27 ± 23.25
89.36 ± 9.20 284.80 ± 23.70
90.85 ± 8.65 299.57 ± 39.07
Cohen’s d
p Value
p2
Post-hoc comparisons
E5M
E5I
I5M
0.058 0.026
0.040 0.051
E5M, E5I E5M, I5M
0.58 0.51
0.42 0.07
0.17 0.46
Data are means ± standard deviation (SD) values. All tests are two-tailed. Pi: the percentage of successful inhibition trials. MANOVA Wilks’ Lambda F ¼ 3.03, df ¼ 4, 276, p ¼ 0.018
CSQ), age differences and the cutoff classification of chronotypes. Nevertheless, the most consistent finding across studies using the SSS-V was the relationship between the disinhibition subscale and the evening types, which was also shown to be significant in the present study. The disinhibition subscale of the SSS-V is more strongly correlated than other subscales to behavioral disinhibition such as alcohol drinking behaviors (Hittner & Swickert, 2006). A core personality trait related to circadian rhythm may be impulsivity related to behavioral inhibition rather than seeking novel stimuli itself. Although impulsivity and sensation-seeking traits may share some personality features and influence each other, they have conceptually and empirically distinct characteristics. Impulsivity is a multifaceted construct consisting of impulsive decision and a lack of inhibitory control (Evenden, 1999). Sensation-seeking, in contrast, refers to the tendency to seek out novel and highly stimulating experiences and the willingness to take risks to attain them (Zuckerman, 1972) which appears to be more related to behavioral approach systems (Poythress et al., 2008). The disinhibition subscale that is typically defined in terms of behavioral disinhibition or undercontrol may reflect a conceptual overlap between the two constructs. A previous study showed that eveningness was associated with impulsivity but not venturesomeness (Caci et al., 2005). Additionally, evening types were related to dysfunctional impulsivity but not functional impulsivity such as extraversion in Dickman’s !
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model (Adan et al., 2010b; Dickman, 1990). Collectively, evening types would rather be involved in impulsivity traits related to behavioral inhibition than seeking novelty or personal gain. Although no single personality dimension is likely associated with psychiatric vulnerability related to circadian rhythms, a core personality trait related to circadian rhythm may be impulsivity of inhibitory control. This can be supported by the present results of GO/ NO-GO paradigm in which evening type subjects had lower level of successful response inhibition (marginal significance, p ¼ 0.058) and morning types had slower reaction times. Deficit of response inhibition is particularly interesting because it is considered a vulnerable marker of bipolar disorders (Roberts et al., 2013) and substance use disorders (Nigg et al., 2006). Impaired response inhibition may mediate dysregulation of circadian rhythms into behavioral disinhibition problems and psychiatric disorders. The present findings need further investigation because they suggest a possible pathophysiological approach to impaired inhibition that may be accessible by circadian interventions such as morning sunlight exposure. The present study had several limitations. First, the classification of circadian preference in the present data relied on self-reported measures of chronotypes. Further replication studies using objective assessments of sleepwake cycles would strengthen the clinical implications of chronotypes on impulsivity traits. Second, the internal consistency of the K-BIS-23 subscales in the
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present sample was not high (Cronbach’s a coefficients: 0.52, 0.70, and 0.46 for non-planning, motor and attention subscales, respectively). As poor fit to the confirmatory model of the factor structures have also been argued in other studies using BIS-11 for other populations (Reise et al., 2013), this may be one limitation and should be interpreted cautiously. Third, the present study with non-experimental cross-sectional design leaves some unanswered questions regarding the links and the underlying mechanisms between chronotypes, and impulsivity and sensation-seeking traits. Finally, our results obtained from healthy volunteers may be difficult to generalize to clinical populations. Future research including clinical samples is needed to reveal the mediating role of chronotypes between dispositional impulsive factors such as inhibitory control and mental illnesses related to impulsivity. Overall, the present results showed significant relationships between circadian preference and the personality traits of impulsivity and sensation-seeking. In particular, high impulsivity, disinhibition of sensationseeking, and impaired response inhibition were related to evening types. Our findings suggest that circadian rhythms might be associated with psychiatric problems interacting with personality traits such as impulsivity and the elevated vulnerability toward impulsivity in evening type subjects supports the need for developing early circadian intervention programs that warn against the consequences of disrupted circadian rhythm and promote healthy sleep hygiene and lifestyle regularity in daily activities. Further clinical and neurobiological studies are needed to demonstrate causality of the effects in question.
DECLARATION OF INTEREST This work was supported by a new faculty research seed money grant of Yonsei University College of Medicine for 2014-32-0009. The authors report no conflict of interest.
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