Person. inditrd. D$ Vol. IO, No. I. pp. 43-50. 1989 Printed in Great Britain. All rights reserved

0191-8869’89 53.00 + 0.00 Copyright c 1989 Pergamon Press plc

HYPERACTIVE BEHAVIOR IN CHILDHOOD AND ADULT IMPULSIVITY: A LONGITUDINAL

STUDY OF MALE SUBJECTS

BRITT AF KLINTEBERG,‘.’ DAVID MAGNUSSON’* and DAISY SCHALLING’.’ ‘Department of Psychology, University of Stockholm. 10691 Stockholm. Sweden

?Department of Psychiatry and Psychology, Karolinska Institute, Stockholm. Sweden

(Receiaed I December 1987)

Summnry-Lately there has been an increasing interest in whether. and to what extent. school age behavior problems have implications for adult personality. In order to elucidate this problem. impulsivity was studied, using the Karolinska Scales of Personality (KSP) Impulsiveness scale. for 77 male Ss at age 2627 years, who had been observed and rated at age 13 years with respect to Aggressiveness. Motor Restlessness, and Concentration Difficulties. Impulsiveness was significantly and positively correlated with Aggressiveness, Motor Restlessness and Concentration Difficulties, and with the sum of the latter two. used as an indicator of Hyperactive Behavior. The association between Hyperactive Behavior and Impulsiveness persisted when Aggressiveness was partialled out from the relationship. Furthermore. in a stepwise regression analysis Hyperactive Behavior was highly related to Impulsiveness, with the motor restlessness component significantly contributing to the prediction. The results are discussed in terms of a model for impulsivity as related to behavioral disinhibition.

INTRODUCTION

In epidemiological surveys of school age behavior problems, about one third of the boys have been described by their teachers as overactive and easily distracted (Rutter, Tizard and Whitmore, 1970). In extreme degrees, these behaviors are the main components of the Hyperactive Syndrome/Attention Deficit Disorder (ADD). This syndrome is one of the most common behavior disorders in boys. Prevalence estimates have varied, at least partly due to the lack of precise definitions of the term hyperactivity and the lack of reliable methods for assessment. In recent years the operational criteria for hyperactivity, “Attention Deficit Disorder with Hyperactivity”, published in the third edition of Diagnostic and Statistical Manual of Mental Disorders (DSM III. American Psychiatric Association, 1980), have been increasingly used. The criteria are (1) excessive general hyperactivity or motor restlessness (poorly organized, differing from the norm for age both in quality and quantity); (2) difficulty in sustaining attention, especially in unstructured situations, frequent ‘forgetting’ of demands made or tasks assigned; (3) impulsive behavior (sloppy work, frequently making a noise, frequently interrupting, difficulty in waiting for one’s turn, low frustration tolerance); and (4) duration of at least 1 year.

In early analyses, aggressive behavior has sometimes been regarded as one aspect of the hyperactive syndrome (Morrison and Stewart, 1971; O’Malley and Eisenberg, 1973). However, later studies have presented support for separating hyperactivity and aggressiveness (McGee, Birbeck and Silva, 1985a; Fuhrman and Kendall, 1986).

Dimensionality of hyperactivity and aggressitleness

Both hyperactivity and aggressiveness may be observed in various degrees in normal school children and may be conceptualized as traits or dimensions (Schachar and Taylor, 1986). McGee and co-workers (McGee, Williams and Silva, 1984; McGee, Williams, Bradshaw, Chapel, Robins and Silva, 1985b) distinguished between children with what they diagnosed as ‘pure’ hyperactive behavior, children with ‘pure’ aggressive behavior, and children with both hyperactive and aggressive behaviors in a study of a large sample of 7-year-old children. They investigated cognitive, behavioral, and developmental characteristics of boys in these subgroups and found that ‘pure’ hyperactive behavior was associated with a more general, long-term, cognitive deficit, while ‘pure’

*To whom correspondence should be sent.

43

44 BRITT AF KLINTEBERG er al

aggressiveness did not appear to be associated with impaired cognition. ‘Pure’ aggressive behavior also tended to be more situation-specific than did hyperactive behavior.

These results suggest a differentiation between the aggressive and hyperactive behavior dimen- sions. the importance of which has been emphasized by several researchers (Loney. Langhorne and Paternite, 1978; Langhorne and Loney, 1979; Milich, Loney and Landau, 1982) and which has received support (Magnusson, 1988; af Klinteberg and Magnusson. 1988) in a study of the differential relationships of ratings of aggressiveness and aspects of hyperactivity to adrenaline excretion in two different situations. Both aggressive behavior and hyperactivity showed a significant negative relationship to adrenaline excretion. However, when hyperactivity was partialled out from aggressiveness, the correlation between ‘pure’ aggressiveness and adrenaline was almost zero in both situations. When aggressiveness was partialled out from hyperactivity the correlation between ‘pure’ hyperactivity and adrenaline was still significant.

Follow-up studies of hyperacticit>v and aggressiveness

Previously, childhood hyperactivity was assumed to disappear at adult age. There is now, however, an increasing interest in whether or not early hyperactivity is related to behavioral disturbances later in life. Robins (1966) found, in a 30-year follow-up study of children seen in a child guidance clinic, that approximately one third of those children showing hyperactive symptoms, including impulsive behavior, were later diagnosed as psychopathic (see also Stewart, Pitts, Graig and Dieruf, 1966; Mendelson, Johnson and Stewart, 1971). On the basis of a review of 17 follow-up and seven follow-back studies. with sample sizes from 9 to 150 Ss and with age range from 10 to 31 years, Thorley (1984) reported that the key symptomatic features of hyperactivity-restlessness, overactivity, and cognitive difficulties-persisted over time. Most studies were at least 5-year follow-ups.

The idea that young hyperactives might be a risk-group for later delinquency problems is suggested by results presented by Magnusson (1987) and Stattin and Magnusson (1984) in a study relating ratings of motor restlessness at the age of 13 years to official records of criminal offences at adulthood. This prognostic implication of the concept confirmed the results in a study by Weiss, Minde, Werry, Douglas and Nemeth (1971). who found a high percentage of serious delinquent behavior in teenage hyperactive children (see also Weiss and Trokenberg Hechtman, 1986; Satterfield, Hoppe and Schell, 1982). In another study August, Stewart and Holmes (1983) compared over 4 years the development of a group of boys with ‘pure’ hyperactivity with that of boys who had both hyperactive and aggressive symptoms. It was found that the ‘pure’ hyperactivity group continued to show mainly inattentive and impulsive behaviors at follow-up, while aggressive and antisocial problems continued in the latter group.

Impulsivity is accordingly one central aspect of the general hyperactivity syndrome. It has been suggested (Rothenberg and Nachson. 1979) that impulsivity rather than aggression against others is the predominant aspect of individual functioning characterizing psychopathic behavior and delinquency. The role of impulsivity in the structure of adult personality has been increasingly discussed (Schalling. Edman and Asberg, 1983; Schalling and Asberg, 1985; Gray, Owen, Davis and Tsaltas, 1983; Barrat and Patton. 1983) and Gray et al. (1983) have proposed that the concept of impulsivity should be studied with and without including aggressive components.

A relevant question is whether or not any particular component of the behavioral dimensions studied in childhood is more related than are other components to adult behavioral disturbances. If so, such information would provide valuable assistance in choosing appropriate therapeutic interventions as well as enhancing the theoretical understanding of adult behavior disorders. Therefore, the aim of the present study is to investigate the long-term relationship, controlling for aggressiveness, between childhood hyperactive behavior and adult impulsivity, an important indicator of adult behavior problems.

METHOD

Subjects

Within the longitudinal research program ‘Individual Development and Adjustment’ the main cohort consists of all boys and girls from one community, who attended grade 3 (about IO years

Hyperactive behavior 45

of age), at the time of the first data collection and comprised a group of about 1100 boys and girls (Magnusson, Dun& and Zetterblom, 1975). At adult age a comprehensive follow-up has been performed (Magnusson, 1987). In the follow-up, a sample of Ss, who can be considered as representative of all school children in the study cite, was studied intensively. Data for the study presented here refer to this sample.

The specific investigation group employed in the following analyses is defined as those boys from whom data were collected at the age of 13 years (behavior ratings) as well as at adult age (self-reported personality). A self-report questionnaire was answered by 86 male Ss at age 26-27 years and of them 77 Ss had complete data from both points in time. A study of the drop out at adult age has not indicated any drop-out bias (Bergman and Magnusson, 1983).

Variables

Data in the study presented in this report concerned Motor Restlessness and Concentration Difficulties (as aspects of the hyperactive syndrome), and Aggressiveness from the age of 13, and Impulsiveness from the age of 26-27.

Ratings on behavior at the age of 13 were obtained from the teachers. Behavior was rated on 7-point scales with verbal descriptions of the extreme manifestations as follows:

Aggressiveness. (A) They are aggressive against teachers and classmates. They may, for example, be impertinent and impudent, actively obstructive or incite to rebellion. They iike disturbing and quarrelling with classmates. (B) They work in harmony with the teacher and have positive contacts with classmates. Their relations to others easily become warm and affectionate.

Motor Restlessness. (A) They find it very difficult to sit still during lessons. They fidget uneasily in their seats or wish to move about in the classroom, even during lessons. They may also be talkative and noisy. (B) They have no difficulty at all in satisfying even great demands on silence and quietness.

Concentration Difficulties. (A) They cannot concentrate on their work, but are occupied with irrelevant things, or sit daydreaming. For a few moments they may work but are soon lost in other thoughts again. They usually give up quickly, even when the work is suited to their level of intelligence. (B) They have a marked ability to concentrate on a task and persevere with it. They never allow themselves to be distracted, and do not give up as long as a task suits their level of intelligence.

Each definition was followed by the following definition: “Most children are between these extremes. The rating scale was constructed as follows: most like behavior B (l--3), mean of class (4) and most like behavior A (5-7)“. The teachers were requested to bear in mind the normal distribution of pupils for the rated variable, and they were instructed to use the boys in their own class as reference group. They were then allowed to adjust for what they judged as normal behavior for boys at this age. This instruction has the effect of lowered between-group variation and possibly weaker correlation coefficients. In most cases the teachers had known and observed the Ss for 3 years and had taught their classes in almost all subjects (Magnusson et al., 1975).

The intercorrelations among the three rating variables are all positive and significant at the 0.001 level, suggesting that these rating variables share a common variance, and test-retest reliability over 3 years has shown relatively high stability over time within the variables (Backteman and Magnusson, 1981). The reliability for the rating variables based on the whole sample in the longitudinal study is conservatively estimated at 0.80 (Magnusson et al., 1975). In a series of other studies within the longitudinal project, the teachers’ ratings have demonstrated high validity.

Hyperactive Behavior. In the regression analyses presented here, the rating scores for Motor Restlessness and Concentration Difficulties were summarized and used as an indicator of Hyperactive Behavior. For further analyses the distributions of scores were dichotomized in each of the two hyperactivity-related rating variables. Boys with scores 5-7 were classified as ‘high’, and those with scores I-4 as ‘low’ on the variable, respectively, yielding four groups. Boys classified as ‘low’ on both Motor Restlessness and Concentration Difficulties formed the non-hyperactive group (cell A in Fig. 1) and boys classified as ‘high’ on both these variables the hyperactive group (cell D in Fig. 1).

Zmpulsivity. Adult impulsivity was assessed by means of the Impulsiveness scale from the KSP (Schalling and Edman, 1987; Schalling, Asberg, Edman and Oreland, 1987; af Klinteberg, Schalling

46 Brurr AF KLINTEBERG el ai.

and Magnusson, 1986), administered to the sample at the age of 2627 years. The item content of the KSP Impulsiveness scale is close to the one of the ‘narrow impulsivity’ factor (Eysenck and Eysenck, 1977) and reflects a tendency to act on the spur of the moment, to make rapid decisions. to display lack of planning, and to exhibit carefreeness (Schalling and Asberg. 1985), all of which are in line with the concept of impulsivity described by Shapiro (1965). The KSP Impulsiveness scale has shown high correlations with other impulsivity scales (see Schalling and .&berg. 1985; Schalling et al., 1983).

Data analysis

Product-moment correlations between ratings of behavior at age 13 years and self-reported adult Impulsiveness, as well as partial correlations between the rating variables and adult Impulsiveness with the other rating variables respectively partialled out, were computed. Furthermore. a 2-way analysis of variance (ANOVA) was carried out to analyze the effects of Motor Restlessness and Concentration Difficulties on adult Impulsiveness. Finally. a stepwise multiple regression analysis, with Motor Restlessness and Concentration Difficulties and their interactions (expressed as dummy variables) as independent variables and adult Impulsiveness as the dependent variable, was performed.

RESULTS

Correlations between behavior ratings and adult impulsivity

The behavior ratings at the age of 13 years were all positively correlated with adult KSP Impulsiveness scale scores, the correlation being for Aggressiveness r = 0.37, P < 0.001, for Motor Restlessness r = 0.37, P < 0.001, and for Concentration Difficulties r = 0.33, P < 0.003. The correlation between the combined Hyperactive Behavior variable and adult Impulsiveness was r = 0.40, P < 0.001.

Hyperactive and aggressive behavior us adult impulsivity

When partial correlations were calculated, the association between Hyperactive Behavior and adult Impulsiveness persisted when Aggressiveness was partialled out (r = 0.20, P < 0.04), whereas there was no relationship between Aggressiveness and Impulsiveness (r = 0.12, NS), when Hyperactive Behavior was controlled.

Eflects of hyperactive behavior ratings on adult impulsivity

The distribution of scores in the variables related to hyperactive behavior was dichotomized, yielding four groups (see Fig. 1). In the ANOVA there was a significant main effect of Motor Restlessness [F(1,73) = 5.04, P < 0.031, not of Concentration Difficulties [F( 1,73) = 2.04, NS], for the KSP Impulsiveness scale, and there was no interaction [F(1,73) = 0.03, NS]. Thus, the higher Impulsiveness scores were found in the groups rated high in Motor Restlessness (cells B and D). The result of a 2-tailed t-test comparison indicated that Ss in the Hyperactive Behavior group (with a combination of high scores in Motor Restlessness and in Concentration Difficulties, cell D) had significantly higher Impulsiveness scores at adult age (t(51) = 3.18, P < 0.01) than did the non-hyperactive group (low scores in both Motor Restlessness and in Concentration Difficulties, cell A).

In a stepwise multiple regression analysis with Motor Restlessness, Concentration Difficulties, and their interactions used as independent variables and adult Impulsiveness as the dependent variable, Motor Restlessness, on the first step of the analysis, was the most important variable, contributing significantly to the prediction of adult Impulsiveness [F( 1,73) = 10.81, P < 0.011. Since Motor Restlessness entered on the first step it takes all of what is unique and in common with that of Concentration Difficulties, entering on the second step in the analysis. This explains a non-significant contribution of Concentration Difficulties [F(2,72) = 2.16, NS]. None of the interaction terms increased prediction. The total multiple regression coefficient was 0.40, explaining 15.4% of the total variance. Corrected for attenuation (with an estimated reliability for the Impulsiveness scale of r = 0.80) the regression coefficient was high (multiple R = 0.49).

47 Hyperactive behavior

? 2L.9 26.8 :0.9 *1 .s

6 (n-15) D (n=13)

22.5 24.0

to.6 r2.0

A (n=bO) C (n-9)

1-L 5-7

CONCENTRATION DIFFICULTIES

Fig. 1. Mean Impulsiveness scale scores at adult age (k standard errors) in four groups of male Ss. yielded by dichotomized rating scores in Motor Restlessness and

Concentration Difficulties at age 13 years.

DISCUSSION

A large body of evidence, both retrospective and prospective, has shown high impulsivity in groups with patterns of biological, behavioral, and psychological deviance (Blackburn, 1969; Lahey, Stempniak, Robinson and Tyroler, 1978; Schalling, 1978). This makes it reasonable to consider high impulsivity an important indicator of susceptibility to antisocial behavior and psychopathology (Schalling, Asberg, Edman and Levander, 1984). Many recent studies of the correlates of the impulsivity dimension imply that it may reflect a vulnerability for ‘disinhibitory’ psychosocial disorders (Schalling et al., 1983; Gorenstein and Newman, 1980).

The correlational pattern and results of the multivariate analyses in the present study give support to the assumption of a connection between early hyperactive behavior and self-reported adult impulsivity. The size of the coefficients is noteworthy, considering the long time, 13-14 years, that passed between the two data collection occasions. This is interesting in view of the results by Conley (1984) who, in a longitudinal study of adult personality, found (1) high stability over time for some personality traits, among which was a combination of impulsivity, psychopathy, and psychoticism, and (2) that a basic personality structure including a factor of impulse control was essentially the same in middle as in early adulthood (Conley, 1985). Furthermore, the present results give some support to the assumption that measures of hyperactive behavior should be studied separately from measures of aggressiveness, since ‘pure’ hyperactive behavior was significantly related to impulsivity in a longitudinal perspective, which was also found by August er al. (1983). The results are interesting from a psychobiological point of view, as it might be assumed that the biological bases for the two variables are different.

Hyperactive behavior has been found to be connected with psychophysiological signs of low cortical arousal (Satterfield, 1978) and low platelet monoamine oxidase (MAO) activity (Shekim, Davis, Bylund, Brunngraber, Fikes and Lanham. 1982), both biological indicators of vulnerability for psychopathy (Schalling, 1978; Lidberg, Modin, Oreland, Tuck and Gillner, 1985). An association has been found between low activity of the platelet MAO enzyme and high self-reported impulsivity in groups of normal Ss (Schalling, Edman, Asberg and Oreland, 1988; af Khnteberg, Schalling, Edman, Oreland and Asberg, 1987) as well as low levels of the serotonin metabolite 5hydroxyindoleacetic acid (SHIAA) in cerebrospinal fluid (CSF) and high scores in scales related to impulsivity, sensation seeking and psychopathy in non-depressed patients (Schalling et al., 1984). This observation is in line with Soubril’s assumption that reduced activity in the serotonergic system is connected with an increase in motor activity level, a shift from control over behavior to impulsivity (Soubrit, 1986). PA,” !“I--u

48 BRITT AF KLINTEBERG et al

The main findings in the present study were that (I) the motor activity component of the Hyperactive Behavior indicator was the important predictor of adult impulsivity and (2) a combination of high scores in Motor Restlessness and in Concentration Difficulties characterized the group with the higher adult impulsivity. The group with high rating scores only in Concentration Difficulties did not differ from the non-hyperactive Ss in impulsivity at adult age. Thus, despite the fact that some researchers have regarded inattention as the core dysfunction of hyperactivity (McGee, Williams and Silva, 1985~) and its maintenance over time as the greater risk factor for development of antisocial behavior (Gittelman, Mannuzza, Shenker and Bongura, 1985) in the present study it does not per se predict self-reported impulsivity in adult life.

In conclusion, the results in this study suggest that early hyperactive behavior is an important antecedent of adult impulsivity, which in turn has been shown to be connected with criminal behavior, alcohol abuse, and other disorders in adults (see Schalling and Holmberg, 1970; Schalling et al., 1984; Rydelius, 1983; Blackburn, 1969; Barrat and Patton, 1983). Boys rated high in hyperactivity-related variables may constitute a potential risk-group for disinhibitory psycho- pathology and delinquency at adult age. The present results also underscore the importance of a pattern approach in the study of developmental issues.

Acknowledgements-The research has been financially supported by grants from the Bank of Sweden Tercentenary Foundation and from the Swedish Council for Research in the Humanities and Social Sciences.

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