David M. Stoff

Subtypes of aggression and their relevance to child psychiatry

OBJECTIVE To review the evidence for qualitatively distinct subtypes of human aggression as they relate to childhood psychopathology. METHOD Critical review of the pertinent literature. RESULTS In humans, as well as in animals, the term aggression encompasses a variety of behaviors that are heterogeneous for clinical phenomenology and neurobiological features. No simple extrapolation of animal subtypes to humans is possible, mainly because of the impact of complex cultural variables on behavior. On the whole, research into subtypes of human aggression has been rather limited. A significant part of it has been conducted in children. Clinical observation, experimental paradigms in the laboratory, and cluster/factor-analytic statistics have all been used in an attempt to subdivide aggression. A consistent dichotomy can be identified between an impulsive-reactive-hostile-affective subtype and a controlled-proactive-instrumental-predatory subtype. Although good internal consistency and partial descriptive validity have been shown, these constructs still need full external validation, especially regarding their predicting power of comorbidity, treatment response, and long-term prognosis. CONCLUSIONS Our understanding and treatment of children and adolescents with aggressive behavior can benefit from research on subtypes of aggression. The differentiation between the impulsive-affective and controlled-predatory subtype as qualitatively different forms of aggressive behavior has emerged as the most promising construct. Specific therapeutic hypotheses could be tested in this context and contribute to a full validation of these concepts.

Neuroendocrine responses to challenge with dl-fenfluramine and aggression in disruptive behavior disorders of children and adolescents

Prolactin (PRL) and cortisol (CORT) responses to a single oral administration (1.0 mg/kg) of the indirect serotonin agonist dl-fenfluramine were assessed in unmedicated prepubertal and adolescent males with disruptive behavior disorders (DBD). Neuroendocrine responses were correlated with scores on aggression rating scales in prepubertal and adolescent DBD patients and compared with those of matched adolescent normal control subjects. Net dl-fenfluramine-induced PRL and CORT release was not correlated with aggression rating scores in prepubertal and adolescent DBD patients and did not differ significantly between adolescent DBD patients and normal control subjects. Although the present study does not demonstrate a serotonergic abnormality in aggression or DBD, this may be more a reflection of limitations of the neuroendocrine challenge test procedures or the methods used than evidence that serotonergic function in the central nervous system is normal in aggression.

Reduction of (3H)-imipramine binding sites on platelets of conduct-disordered children.

Binding characteristics of tritiated imipramine on blood platelets were determined in daytime hospitalized prepubertal children who had mixed diagnoses of conduct disorder (CD) plus attention deficit disorder hyperactivity (ADDH) and in inpatient adolescents who had a history of aggressive behavior. The number of (3H)-imipramine maximal binding sites (Bmax) was significantly lower in the prepubertal patient group of CD plus ADDH; the dissociation constant (Kd) was not significantly different. There were significant negative correlations between Bmax and the Externalizing or Aggressive factors of the Child Behavior Checklist when the CD plus ADDH prepubertal patients were combined with their matched controls and within the adolescent inpatient group. We propose that a decreased platelet imipramine binding Bmax value, as an index of disturbed presynaptic serotonergic activity, is not specific to depression and may be used as a biologic marker for the lack of behavioral constraint in heterogeneous. populations of psychiatric patients.

Instrumental and hostile aggression in childhood disruptive behavior disorders

An analogue task of instrumental and hostile aggression during a competitive game was evaluated in a sample of clinically-referred 8-to 12-year-old aggressive boys. Similar to a prior task in a normative sample (Having, Wallace, & La Forme, 1979), both types of aggression increased during provocation as compared to baseline, indicating the success of the provocation manipulation, with moderate correlations between the two aggressive responses. The aggressive group with attention-deficit hyperactivity disorder (ADHD) and the aggressive group without ADHD each had higher rates of instrumental aggression than controls. Only the aggressive/ADHD group had higher rates of hostile aggression than controls. Parent Child Behavior Checklist ratings indicated a modest but significant unique relationship between instrumental aggression and delinquency. The high rate of both types of aggression in the aggressive/ADHD group suggests that comorbid ADHD and aggression may result in qualitative differences in aggressive behavior. The high rate of hostile aggression in the aggressive-ADHD group supports theoretical assumptions regarding the relationship of hostile aggression to poor impulse control.

Decrease in plasma tryptophan after tryptophan-free amino acid mixtures in man

Male healthy subjects, fasting 12 hours, ingested increasing amounts of a mixture containing a fixed proportion of seven essential amino acids (L-isoleucine 11.5%, L-leucine 18.0%, L-lysine 13.1%, L-methionine 18.0%, L-phenylalanine 18.0%, L-threonine 8.2%, L-valine 13.1%) and lacking tryptophan. The diets produced a rapid fall in plasma tryptophan which was proportional to the total amount of the amino acids ingested. Following the highest dose administered (36.6 g) plasma tryptophan fell to a minimum of about 35% the initial level and remained markedly reduced at 6 hours after treatment. The mechanism of this decrease and its potential clinical relevance are discussed.

Distinguishing instrumental and hostile aggression: does it make a difference?

An analogue task of instrumental and hostile aggression during a competitive game, modified to minimize overlap between aggressive responses, was evaluated in 8- to 14-year-old clinically referred boys (n=33). Postgame interviews indicated that the hostile response, an aversive noise, was perceived by over 80% of subjects as hostile and not instrumental. In contrast, the instrumental response, blocking the opponents game, was perceived about equally as having instrumental and hostile functions. The hostile aggressive response was uniquely correlated with continuous performance task impulsive commission errors (r=51), which supported the theoretical relation of hostile aggression to poor impulse control. These results suggest that instrumental and hostile aggression can be distinguished and when precisely defined are distinct in theoretically important ways.

Platelet imipramine binding and serotonin uptake in obsessive-compulsive patients.

Platelet imipramine binding was measured in 16 drug‐free nondepressed patients (aged 20‐61 years, mean ± SD 35 ± 8) suffering from obsessive‐compulsive disorder (OCD) and in 16 sex‐, race‐ and age‐matched healthy controls. Imipramine binding capacity and affinity were not different in the 2 groups. Platelet serotonin (5‐HT) uptake capacity, Vmax, was also measured in 15 of these patients and their matched controls. Vmax was significantly higher in the patients (309 ± 149 pmol/109 cells/min) than in the controls (181 ± 110). An increase in platelet 5‐HT uptake supports the involvement of 5‐HT in OCD and may suggest that a hyperactive serotonergic system is present in this disorder.

Elevated Platelet MAO is Related to Impulsivity in Disruptive Behavior Disorders

Platelet monoamine oxidase (MAO) activity was measured in 32 drug-free prepubertal boys with externalizing symptoms of disruptive behavior disorders and 47 boys with no DSM-III-R diagnoses, and correlated to questionnaire and laboratory performance measures of impulsivity. A subgroup of boys with high MAO activity exhibited significantly poorer performance (i.e., more impulsivity) than a subgroup of low MAO activity on laboratory tasks requiring response inhibition. High MAO patients were more impulsive than high MAO controls on some performance tasks and elevated platelet MAO was unrelated to personality questionnaire measures of impulsivity or to patient status. These data suggest that biological markers such as MAO activity may correlate better with performance than clinical questionnaire measures. Abnormally high platelet MAO activity may not be sufficient to produce externalizing symptoms in children, perhaps interacting with an underlying behavioral dimension of impulsivity.

Test-retest reliability of the prolactin and cortisol responses to D,L-fenfluramine challenge in disruptive behavior disorders

We examined the intraindividual stability of plasma prolactin (PRL) and cortisol responses to D,L-fenfluramine challenges (1.0 mg/kg, p.o.), at a 1-week interval, in boys with disruptive behavior disorders. Two acute administrations of fenfluramine produced consistent and predictable effects on net prolactin responses (peak delta PRL, area under the curve delta PRL), but variable and unpredictable effects on net cortisol responses. The time course and magnitude of fenfluramine blood levels, not nor-fenfluramine, paralleled net PRL responses to fenfluramine. These data indicate that the PRL response to fenfluramine shows continuity within individuals over the course of 1 week, providing a reliable index to reflect the overall function of the serotonin system in the limbic-hypothalamus.

Platelet 3H-imipramine binding, serotonin uptake, and plasma α1 acid glycoprotein in disruptive behavior disorders ☆ ☆☆

Tritiated imipramine labels with high affinity a recognition site associated with the serotonergic transporter in blood piatelets (Langer and Galzin 1988). Concomitant measurement of platelet 3Himipramine binding (IB) and 3H-5-hydroxytryptamine (5-HT) uptake in various diseases does not usually reveal parallel changes in these parameters. De~ eased platelet 5-HT uptake without accompanying changes in platelet IB has been observed in depression or schizophrenia (Wood et al 1983), panic disorder (Pecknold and Suranyi-Cadotte 1986), alcoholic cirrhosis (Ahtee et al 198 ! ), hypertension (Kamal et al 1984), Alzheimcrs dis~a~ (Suranyi-Cadotte et al 1985), and Parkinsons disease (Suranyi-Cadotte et al 1985). Decreased platelet IB but no corresponding changes in platelet 5-HT uptake has been found in depressed women (Roy et al 1987) and adolescents with obsessive--compulsive disorder (Weizman et al 1986a), anore,da nervosa