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Aims: The purpose of the present study was to assess patterns of temperament and character in a clinical sample of Korean children with attention-deficit hyperactivity disorder (ADHD) and to investigate the relationship between patterns of temperament and character and the severity of ADHD symptoms.
Methods: Fifty-one children who met DSM-IV criteria for ADHD and 51 age- and sex-matched healthy comparison subjects completed the Junior Temperament and Character Inventory (JTCI) and the DuPaul's ADHD Rating Scale (ARS-IV).
Results: Children with ADHD had significantly higher scores of Novelty Seeking and lower scores of Self-directedness in both parents' rating and children's self-rating. In addition, low Self-directedness scores predicted higher total scores of ARS-IV.
Conclusions: In a clinical sample of Korean children with ADHD, a distinct pattern of temperament and character was found. The current findings suggest that low Self-directedness may be related to the severity of ADHD symptoms.
ATTENTION-DEFICIT HYPERACTIVITY disorder (ADHD) is characterized by developmentally inappropriate inattention, impulsivity, and hyperactivity.1 It has been considered as a highly heritable but clinically heterogenous disorder with earlier onset of symptoms before 7 years of age, suggesting the continuity between temperament and ADHD.2 Moreover, considering its persistence into adulthood and developmental outcome,3 exploring the relationship between character and ADHD may be needed.
The biosocial model of Cloninger's temperament and character is based on biogenetic hypotheses underlying human behaviors. Temperament dimensions of Novelty Seeking, Harm Avoidance, Reward Dependence, and Persistence have been reported to be genetically independent from one another, moderately heritable and stable across time.4,5 Each represents specific stimulus–response characteristics. Character dimensions include Self-directedness, Cooperativeness, and Self-transcendence. Each refers to individual differences in self-concepts, goals, and values. In contrast to temperament, character has been regarded as being more influenced by social learning rather than by genetic factors. It is expected to mature during the developmental stages throughout the lifespan.4
Several studies have investigated patterns of temperament and character in subjects with ADHD. McIntosh reported that children with ADHD had temperaments with higher activity levels, higher distractibility, and lower persistence compared to healthy peers using the Temperament Assessment Battery for Children.6 Recently, lower task orientation and higher activity were related to ADHD versus controls using the Revised Dimensions of Temperament Scale–Child.7 In addition, adults with ADHD had high scores in extraversion and neuroticism among the big five personality traits,8 which were thought to correlate with Novelty Seeking and Harm Avoidance, respectively.9,10
In line with this finding, Downey et al. reported that adults with ADHD scored higher on Novelty Seeking and Harm Avoidance scales using the Tridimensional Personality Questionnaire (TPQ).4,11,12 Using the Junior Temperament and Character Inventory (JTCI),13 Tillman et al. found that patterns of temperament and character in children with bipolar disorder were similar to those in children with ADHD.14 However, although major depressive disorder was excluded, other concurrent comorbidities including anxiety disorder, which may also influence patterns of temperament and character,15 were not sufficiently considered in that study. In addition, sociocultural differences across ethnicity or sample source should be considered in interpreting these findings. Our group has recently reported on the patterns of temperament and character in Korean children with higher ADHD symptoms in the community,16 which also needs to be confirmed in a clinical sample of children with ADHD.
Until now, the relationship between temperament and character or personality and the severity of ADHD symptoms has been studied in the adult population.17,18 In addition, the associations between temperament and the diagnosis of ADHD or other related conditions have been suggested in children.15 Recently, in a community sample of Korean children with higher ADHD symptoms, our group found some correlation between temperament and character and the severity of ADHD symptoms including inattention and hyperactivity–impulsivity.16 But the correlation has not been investigated in a clinical sample of children with ADHD.
The aim of the present study was to evaluate biogenetic temperament and character in a clinical sample of Korean children with ADHD, using a Korean version of the JTCI.19 In addition, a specific relationship between patterns of temperament and character and the severity of ADHD symptoms was investigated. Based on prior reports, we hypothesized that ADHD children will have higher Novelty Seeking, lower Reward Dependence, and lower Persistence in temperament (hypothesis 1) and lower Self-directedness and lower Cooperativeness in character (hypothesis 2) relative to healthy comparison subjects. As an auxiliary hypothesis, we expected that there would be correlations between characteristics of temperament and character and the severity of ADHD symptoms in the present sample (hypothesis 3).
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Demographic and clinical characteristics are presented in Table 1. Forty-four children (86.3%) with ADHD had never taken any psychotropic medication and seven children (13.7%) were not treated with psychotropic drugs in at least 2 weeks preceding evaluation.
Table 1. Characteristics of children with ADHD and healthy comparison subjects
| ||Children with ADHD (n = 51) Mean ± SD||Healthy comparison subjects (n = 51) Mean ± SD|
|Age (years)||10.0 ± 2.0||10.3 ± 0.7|
| Male, n (%)||46 (90.2)||46 (90.2)|
| Female, n (%)||5 (9.8)||5 (9.8)|
| Combined type||22||–|
| Predominantly inattentive type||15||–|
| Predominantly hyperactive-impulsive type||4||–|
| Not otherwise specified||10||–|
| Oppositional defiant disorder||10 (1, past)||–|
| Enuresis||6 (3, past)||–|
| Total score||26.1 ± 11.9||–|
| Inattention subscale score||15.7 ± 7.1||–|
| Hyperactivity-impulsivity subscale score||10.4 ± 6.1||–|
Scores of the JTCI are presented in Fig. 1. Overall correlations of JTCI scores between children's self-rating and parents' rating were significant in all dimensions (r = 0.252–0.338, P < 0.05). In parents' rating, children with ADHD had higher scores in Novelty Seeking and lower scores in Persistence, Self-directedness, and Cooperativeness than healthy controls (independent t-test: d.f. = 100, t = 5.810, P < 0.001; d.f. = 100, t = −4.347, P < 0.001; d.f. = 100, t = −5.559, P < 0.001; d.f. = 100, t = −3.917, P < 0.001, respectively; Fig. 1a). In addition, on children's self-rating, children with ADHD had higher scores in Novelty Seeking and Self-transcendence and lower scores in Reward Dependence and Self-directedness than healthy controls (d.f. = 100, t = 2.555, P = 0.012; d.f. = 100, t = 2.942, P = 0.004; d.f. = 100, t = −2.073, P = 0.041; d.f. = 100, t = −2.312, P = 0.022, respectively; Fig. 1b). In parents' rating of Reward Dependence and Self-transcendence and children's self-rating of Persistence, there were tendencies toward lower scores in children with ADHD (d.f. = 100, t = −1.906, P = 0.060; d.f. = 100, t = −1.689, P = 0.094; d.f. = 100, t = −1.763, P = 0.081, respectively).
Figure 1. Comparison of Junior Temperament and Character Inventory (JTCI) Scores reported by (a) parents and (b) children. (▪) Children with ADHD; (□) healthy control subjects. ADHD, attention-deficit hyperactivity disorder; C, Cooperativeness; NS, Novelty Seeking; HA, Harm Avoidance; P, Persistence; RD, Reward Dependence; SD, Self-directedness; ST, Self-transcendence. Results are reported as mean with 95% confidence interval otherwise indicated. *P < 0.05; **P < 0.01; ***P < 0.001.
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Hierarchical multiple regression was performed to examine the influence of temperament and character on symptoms in children with ADHD controlling for age and sex (Tables 2,3). In both parents' rating and children's self-rating, only low Self-directedness scores significantly predicted higher total scores in ARS-IV, indicating more severe symptoms, controlling for age and sex (in parents' rating, multiple regression analysis, β, standardized regression coefficients = −0.356, t = −2.164, P = 0.036; in children's self-rating, β = −0.342, t = −2.041, P = 0.048). In detailed analysis, Self-directedness scores had negative correlations with both hyperactivity–impulsivity scores and inattention scores (parents' rating, β = −0.312, t = −1.878, P = 0.067; β = −0.327, t = −1.976, P = 0.055; children's self-rating, β = −0.333, t = −2.001, P = 0.052; β = −0.286, t = −1.687, P = 0.099, respectively). But scores of other scales in the JTCI (Novelty Seeking, Persistence, and Cooperativeness in parents' rating and Novelty Seeking, Reward Dependence, and Self-transcendence in children's self-rating) could not predict any scores including total scores, hyperactivity–impulsivity scores, and inattention scores in ARS-IV.
Table 2. Influences of temperament and character on symptom severity in children with ADHD (parent's report)
|Total score||Novelty seeking||−0.082||−0.483||0.632|
|Inattention subscale score||Novelty seeking||−0.057||−0.332||0.742|
|Hyperactivity–impulsivity subscale score||Novelty seeking||−0.094||−0.544||0.589|
Table 3. Influences of temperament and character on symptom severity in children with ADHD (children's self-report)
|Total score||Novelty seeking||0.007||0.040||0.968|
|Inattention subscale score||Novelty seeking||−0.052||−0.292||0.772|
|Hyperactivity–impulsivity subscale score||Novelty seeking||0.074||0.422||0.675|
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In the present study we found that children with ADHD had higher Novelty Seeking and lower Self-directedness relative to healthy controls in both parents' and children's self-rating. In addition, lower Persistence and lower Cooperativeness in parents' rating and lower Reward Dependence and higher Self-transcendence in children's self-rating were found in children with ADHD. The patterns in the current study are in partial accord with those in previous studies regarding the biogenetic temperament and character in both children and adults with ADHD.11,12,14,16
Downey et al. reported that adults with ADHD scored higher Novelty Seeking11,12 and Harm Avoidance12 than the established US norm using the TPQ. In their detailed analysis, ADHD adults with comorbidity scored lower than those without comorbidity on the TPQ, including pessimism and fatigability subscales in Harm Avoidance and dependence subscale in Reward Dependence. In addition, ADHD adults without comorbidity scored lower than 1 SD below the established US norm only on the TPQ pessimism subscale. Therefore, the higher Harm Avoidance seems to be due to the higher rate of comorbid anxiety or depressive disorders in the Downey et al. sample (47.4% of total ADHD subjects).
In the Tillman et al. study parent-reported data showed that children with ADHD were more Cooperative than children with bipolar disorder.14 In addition, while there were no differences in their child-reported data; children with ADHD had higher Novelty Seeking, less Reward-dependence less Persistence, less Self-directed, and less Cooperativeness than normal controls in the parent-report data.
Our group has recently reported that community children with higher ADHD symptoms, whose ARS-IV score were above the 90th percentile of the total study population, had higher Novelty Seeking and lower Self-directedness and Cooperativeness in both parents' and children's rating as well as lower persistence in parents' rating only.16 In summary, the current results support the idea that specific patterns of temperament and character may exist in children with ADHD across ethnicity and sample source.
Although the patterns in the parent rating were the same as the current results, a few different patterns were also found in children's rating in our prior reports in the community.16 The differences in the children's rating may be partly explained by the following reasons. The current study was based on clinically referred subjects, who represent a subgroup of greater symptoms and subjective distress. In addition, in our previous study the formal diagnosis was not made because subject selection was based on ARS-IV score only; risks for false-positive diagnosis and influences of other comorbid psychopathology could be inevitable. Although overall correlations were maintained satisfactorily (r = 0.252∼0.338, P < 0.05), there were statistical discordances between parent–child report of temperament and character other than Novelty-Seeking, Harm Avoidance, and Self-directedness. The statistical discordances between children's and parents' report in the current study are consistent with previous studies.14,27 And because the Cronbach alpha for the subscales of the Korean version of the JTCI is relatively low compared to the adult TCI,19 readers should be cautious in interpreting the present findings.
High Novelty Seeking has consistently been reported in children and adults with ADHD,11,12,14,16 as well as in parents with a history of ADHD who had an ADHD-affected sib pair.18 Novelty Seeking is linked to behavioral activation and describes a genetic disposition towards being excitable, impulsive, exploratory, and quick tempered.5 It has been considered to be related to monoaminergic neurotransmitters.28 Currently the associations among Novelty Seeking, DRD4, and ADHD have been a topic of interest and debate.11,29 Future studies are needed to investigate to what extent these monoamine-related genes including DRD4, play a role in the genetic liability to ADHD, Novelty Seeking, or both.
The present results also indicate that greater severity of ADHD symptoms may be explained by low Self-directedness of children with ADHD. Self-directedness refers to self-determination and willpower, or the ability of an individual to control, regulate, and adapt behavior to fit the situation in accord with individually chosen goals and values.5 Low Self-directedness has been associated with various mental health problems including juvenile delinquency and eating disorder as well as ADHD in children and adolescents, and is expected to exist across externalizing disorders.16,30–32 The symptom severity in the present clinical sample might be outcomes of low self-directedness in character, along with adverse environmental influences associated with children with ADHD even in childhood.
Limitations of the current study are as follows. First, it was not possible to test developmental changes of the association between temperament and character and the severity of ADHD symptoms due to the cross-sectional nature of the symptoms. Second, although the results were in partial accord with those in previous studies, they may not be easily generalizable to other sociocultural environments. Third, we recruited children from clinical settings for ADHD who might have different patterns of temperament and character and symptom severity, which limits the use of these findings in the community. Fourth, because of the small sample size, the current findings may not be replicated in the future, large-scale studies.
In summary, the present study reports specific patterns of temperament and character and their association with symptom severity in children with ADHD. In the future, in order to investigate the association among patterns of temperament and character, symptom severity in childhood and adolescence, and the later psychosocial outcome in adulthood, recruitment of cohorts with longitudinal follow-up on a large scale are needed.