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Effect of ethanol on aggression and timidity in mice.

The effects of ethanol (0.4, 0.8, 1.6, and 2.4 g/kg p.o.) on behavior of aggressive, timid, and sociable male mice treated with the drug on paired interactions with non-aggressive males given water were investigated. Under control interactions, aggressive mice attacked their partners, timid mice showed defensive-escape activities though their partners were completely non-aggressive, and sociable mice intensively investigated their partners. A low dose of ethanol (0.4 g/kg) increased while higher doses (0.8 to 2.4 g/kg) reduced aggressive activities in aggressive mice. Ethanol (0.8 g/kg) also evoked aggressive behavior in non-aggressive timid mice but no dose of ethanol stimulated aggression in non-aggressive sociable mice. Ethanol altered timid defensive-escape activities only in the highest dose of 2.4 g/kg: this dose increased defences and escapes in aggressive males while it reduced defensive upright postures in timid mice. However, 2.4 g/kg of ethanol reduced also another upright movement (exploratory rearing) in timid mice. Sociable activities were not increased by any dose of ethanol tested. By contrast, 0.4 g/kg of ethanol reduced sniffing and following partners in sociable mice. Thus, ethanol exhibit relatively strong aggression-stimulating effects in aversively disposed subjects while the drug was not able to supress timid defensive escape behavior and to stimulate active non-aggressive contacts between strange male mice.

Aggression↗

Limbic system seizures and aggressive behavior (superkindling effects).

This study was done to further analyze the neural mechanisms underlying aggressive behavior associated with psychomotor or temporal lobe seizures. The studies revealed that superkindling the aggressive system by sequential stimulations at seizure-inducing thresholds, of two or more sites in the limbic, hypothalamic, and basal ganglia structures facilitated the production of aggressive seizures. Aggressive behavior in the freely moving cat was evaluated in relation to the occurrence of hissing and growling during stimulation, after-discharge and postictal period. The behavior was correlated with the frequency of the elicited seizures and the seizure durations. Aggression did develop as a component behavioral manifestation of the limbic (psychomotor) seizure. Development of aggressive seizures was facilitated by "priming" the aggressive system. Optimum levels of aggressive behavior occurred with seizures of medium duration. Catecholamine blockers tended to attentuate the occurrence of aggression, whereas the agonist tended to facilitate it. Once the aggressive system was rendered hyperexcitable, exteroceptive stimuli also evoked aggressive attack behavior. It was concluded that repeatedly recurring limbic system seizures through superkindling mechanisms can eventually render the limbic-basal ganglia-preoptico-hypothalamic aggressive system hyper-responsive to both recurring seizures and to exteroceptive stimuli with resulting aggressive behavior with or without an accompanying seizure.

Aggression↗

Escalated aggression as a reward: corticosterone and GABA(A) receptor positive modulators in mice.

RATIONALE: Individuals seek out the opportunity to fight, but the mechanisms behind this positively reinforcing effect of aggression have yet to be understood. OBJECTIVES: The aims of this study were to (1) describe behavioral and corticosterone elevations that occur in aggressive mice conditioned to respond for the opportunity to fight another mouse, (2) determine if corticosterone elevations are necessary for operant responding and escalated aggression, and (3) determine if corticosterone elevations alter the aggression-heightening effects of gamma-aminobutyric acid (GABA)(A) receptor positive modulators. METHODS AND RESULTS: Aggressive male CFW mice were conditioned to respond under the control of a fixed-interval 10-min (FI10) schedule that reinforced their operant behavior by the presentation of an intruder mouse into their home cage. After the FI10, aggressive behavior was ca. 75% higher than the species-typical levels of fighting and plasma corticosterone was more than twice as high after briefly fighting and/or responding on the FI10 schedule. Inhibition of corticosterone synthesis by metyrapone (30-100 mg/kg) reduced both conditioned responding as well as the aggressive behavior after the FI. Although the benzodiazepine midazolam (0.3-3 mg/kg) heightened species-typical aggressive behavior, it did not increase the high level of aggression engendered by the FI schedule. However, midazolam (0.3 mg/kg) and the neurosteroid allopregnanolone (17 mg/kg) both heightened aggression when given after corticosterone synthesis inhibition by metyrapone (56 mg/kg). CONCLUSIONS: These data suggest that corticosterone elevations are required for responding that is motivated by aggressive behavior and for escalated aggression that follows this responding. Corticosterone elevations also appear to inhibit the aggression heightening effect of GABA(A) receptor positive modulators.

Aggression↗

Phenotyping of aggressive behavior in golden retriever dogs with a questionnaire.

Reliable and valid phenotyping is crucial for our study of genetic factors underlying aggression in Golden Retriever dogs. A mail questionnaire based on the Canine Behavioral Assessment and Research Questionnaire (CBARQ; Hsu and Serpell, 2003, JAVMA 223(9):1293-1300) was used to assess behavioral phenotypes. Owners of 228 Golden Retrievers completed the questionnaire. These dogs had been referred to our clinic for aggression problems several years earlier or they were related to aggressive dogs. In this paper, three sets of results are presented, which indicate that behavior scores from the CBARQ can be applied to genetic studies. First, factor analysis demonstrated that CBARQ items can be grouped into 10 behavioral traits, including three types of aggression: stranger-directed aggression, owner-directed aggression, and dog-directed aggression. The results were remarkably similar to those reported by Hsu and Serpell. The aggression scores showed considerable variation in our dog families, which is a prerequisite for genetic studies. Second, retrospective questions enabled us to study changes in the aggressive behavior of the dogs in the course of time. After an average time interval of 4.3 years, over 50% of the dogs had become less aggressive. Third, we analyzed data obtained with an aggression test of 83 dogs. Two out of the three CBARQ aggression factors were also found in the aggression test data.

Aggression↗

Neurobiological mechanisms controlling aggression: preclinical developments for pharmacotherapeutic interventions.

Current pharmacotherapeutic approaches to the management of violent and aggressive behavior rely mostly on agents that act as receptor agonists or antagonists at subtypes of brain dopaminergic, GABAergic, and serotonergic receptors. Ethological experimental studies in animals have shown that drugs may modulate aggression by inhibiting motor activity, by distorting aggression-provoking or -inhibiting signals, by fragmenting behavioral sequences or temporal patterning, or by increasing the rate and intensity of aggressive acts. Evidence from animal studies points to large changes in selected brain dopamine, serotonin, and GABA systems during and following aggressive and defensive behavior. However, the specificity of drugs that are currently used to control aggressive behavior through their action as agonists or antagonists at subtypes of dopamine, serotonin or GABA receptors continues to be of concern. Similar to the effects of widely used traditional neuroleptics that nonselectively antagonize dopamine receptors, the range of behaviors which is suppressed by either D1 or D2 receptor antagonists is pervasive. At present, systemic administration of dopamine receptor antagonists in animal preparations does not target aggression-specific mechanisms. The GABAA/Benzodiazepine/Chloride ionophore receptor complex is implicated in the aggression-heightening effects of alcohol and benzodiazepines. Although early reports focused on the "taming" effects of benzodiazepine anxiolytics, low doses may enhance aggression in both animals and humans. Benzodiazepine antagonists block heightened aggression after low doses of alcohol or benzodiazepines. Agonists at certain 5-HT1 receptor subtypes such as eltoprazine are potently effective in reducing aggressive behavior of males and females of various animal species under conditions that promote charging offensive-type aggression, without adversely affecting nonaggressive components of the behavioral repertoire. However, recent reports indicate that eltoprazine and related compounds may potentiate anxiety reactions in rodents, and question the behavioral specificity of these substances. Opioid receptor antagonists modulate primarily physiological and behavioral responses of defense and submission. Defeated animals show tolerance to opiate analgesia and withdrawal responses upon challenge with opioid receptor antagonists. Defensive and submissive vocalizations are potently blocked by opioid peptides. Substances that target specific receptor subtypes at serotonergic, GABAergic and opioidergic synapses are most promising for the selective modification of aggressive, defensive and submissive behavior patterns.

Aggression↗

Chronic treatment with eltoprazine does not lead to tolerance in its anti-aggressive action, in contrast to haloperidol.

The behavioral effects of eltoprazine and haloperidol during a 4 week treatment period were studied in the resident-intruder model of aggression in male rats. Eltoprazine, a serotonergic (5-HT1A/1B) agonist with specific anti-aggressive actions in animals, was compared to haloperidol, a neuroleptic often used to control behavioral disorders. Eltoprazine (1 or 3 mg/kg p.o.) and haloperidol (2 mg/kg p.o.) were given 60 min before a 10 min aggression test. Acutely, eltoprazine reduced aggression, without adversely affecting other behaviors. Eltoprazine (1 or 3 mg/kg p.o.) was subsequently given daily for 4 weeks and aggression tests were performed each week. The anti-aggressive effects of eltoprazine remained stable over the period of 4 weeks whereas exploration was increased. After a wash-out period of 1 week aggression had returned to baseline levels. Acutely given, haloperidol (2 mg/kg p.o.) completely reduced aggression concomitant with massive sedation. Significant tolerance developed to the sedatory actions of haloperidol over the 4 week treatment period. Aggression returned slowly, but remained below baseline values. One week after wash-out a new challenge with haloperidol (2 mg/kg p.o.) revealed significant tolerance. After 2 weeks wash-out aggression had returned to baseline. The data demonstrate persistent and specific anti-aggressive effects after eltoprazine showing no tolerance. In contrast, haloperidol showed tolerance and rebound effects for aggression. The development of tolerance after haloperidol has a different course for sedation than for the anti-aggressive action.

Aggression↗

Steroid hormones and aggression in female Galápagos marine iguanas.

We studied steroid hormone patterns and aggression during breeding in female Galápagos marine iguanas (Amblyrhynchus cristatus). Females display vigorously towards courting males after copulating (female-male aggression), as well as fight for and defend nest sites against other females (female-female aggression). To understand the neuroendocrine basis of this aggressive behavior, we examined changes in testosterone (T), estradiol (E2), corticosterone (CORT), and progesterone (P4) during the mating and nesting periods, and then measured levels in nesting females captured during aggressive interactions. Testosterone reached maximal levels during the mating stage when female-male aggression was most common, and increased slightly, but significantly, during the nesting stage when female-female aggression was most common. However, fighting females had significantly lower T, but higher E2 and P4, than non-fighting females. It remains unclear whether these changes in hormone levels during aggressive interactions are a cause or a consequence of a change in behavior. Our results support the "challenge hypothesis", but suggest that E2 and/or P4 may increase in response to aggressive challenges in females just as T does in males. Females may be rapidly aromatizing T to elevate circulating levels of E2 during aggressive interactions. This hypothesis could explain why non-fighting females had slightly elevated baseline T, but extremely low E2, during stages when aggressive interactions were most common. Although P4 increased rapidly during aggressive encounters, it is unclear whether it acts directly to affect behavior, or indirectly via conversion to E2. The rapid production and conversion of E2 and P4 may be an important mechanism underlying female aggression in vertebrates.

Aggression↗

[Girls are more successful than boys at the university. Gender group differences in models integrating motivational and aggressive components correlated with Test-Anxiety].

It is surprising to note the evolution of success rates in Belgian universities especially in the first Year. Men are less successful than women and the differences are escalating in an alarming way. Dropouts take the same direction and women now represent a majority of the students at the university. In a previous study, we assessed 616 students in the first Year at the university of Liège with Vasev, the English name of which was TASTE, a self report questionnaire constituted of 4 factors: anxiety, self confidence, procrastination and performance value; anxiety particularly concerned somatic expression of students before and during test evaluations; self confidence was a cognitive component close to self efficacy; procrastination was the behavioral component characterizing avoidance when students are confronted with the risk of failure; performance value referred to intrinsic and extrinsic motivations. French validation of TASTE led to an abbreviated version of 50 items (THEE) consisting of 5 factors, the four of TASTE and an additional one, very consistent, at first called depression because of its correlations with this dimension, then called sense of competence on account of its semantic content. Self-competence has been described in the literature of Achievement Motivation and corresponded to expectancy and ability beliefs in performance process which was also relevant to self-efficacy except the particularity of comparison with others, which was not included in the last construct. Self-competence has been considered as an important part of the Worry component of test anxiety. Some Authors didn't hesitate to view causality flowing from self-competence to test anxiety and have conceptualized the latter as a failure of the self where one's sense of competence has been undermined as a result of experienced failure. In our study, only that factor was equally scored in women and men whereas it was scored higher in failed students. In other respects anxiety and performance value were scored higher in women, self-confidence and procrastination higher in men. Because TASTE didn't discriminate the different components of motivation (performance value referred to intrinsic and extrinsic motivations without precise distinction) we decided to use the MPS (Multidimensional Perfectionism Scale) which gave the opportunity to distinguish SOP (Self Oriented Perfectionism) ie, the self-imposed unrealistic standards with inability to accept faults in order to know and master a subject, that corresponded to intrinsic motivation; SPP (Socially Prescribed Perfectionism) ie, the exaggerated expectancies of others which are subjectively believed as imposed and uncontrollable leading to anxiety, feelings of failure or helplessness, that corresponded to extrinsic motivation; POO (Perfectionism Oriented to Others) ie, the unrealistic demands expected from significant others, which especially characterized males. We assumed that women attached more importance to succeed and submitted more to society exigencies. That way extrinsic and intrinsic motivations were probably more combined unlike men who, dreading a loss of self esteem, tried to avoid failure responsibility in using self handicapping or aggressive behaviours, so separating motivation in an extrinsic part turned to performance value and an intrinsic one more concerned by self confidence and sense of competence with the result that the motivational balance was surely disrupted in case of high competition leading to failure or avoidance. In another previous study we established a structural model illustrating, according to gender, correlations between anxiety, sense of incompetence, self-oriented perfectionism and socially prescribed perfectionism. Self-oriented perfectionism was less correlated to socially prescribed perfectionism in boys than in girls; furthermore especially by those who had never failed, it was negatively correlated to sense of incompetence, thus leading to lower scores of anxiety while in girls, by contrast, such a correlation didn't exist, thus involving higher anxiety. That way, on the one hand, intrinsic and extrinsic motivations by female students complementarily operated on the sense of incompetence and consequently on anxiety, the emotional component of test anxiety; on the other hand, by male students, intrinsic motivation had a negative correlation with the sense of incompetence and a lower correlation with extrinsic motivation, thereby shedding some light on the problem of anxiety level differences according to gender. More, that observation corresponded well to the model of self-worth where test anxiety was understood as a manifestation of perceived incompetence and as a defensive way to ward off negative self-evaluation; that model suited particularly well to boys and explained their attempts to maintain self-worth when risking academic failure. The present research assumes that independence or combination of motivation components is also correlated to different expressions of aggressiveness: hostility corresponding to threat and characterizing more girls while physical aggression is corresponding to personal challenge, a more masculine attribution. If fighting against the sense of incompetence actually characterizes men and consequently shows too the competitive aspects of performance strong enough to mobilize intrinsic motivation, what would be expected regarding the notion of threat suspected to be predominant in girls? The idea of using a questionnaire discriminating the specific dimensions of aggressiveness in fact the Aggression Questionnaire should meet the following purposes: At first establish a French version of that aggression questionnaire, perform the factorial analyses and internal consistency, compare them with other previous samples, then differentiate gender in general and in failure versus success situations. Finally include the different components of aggressiveness in the first described model and build a new one liable to define in boys the explicit pathways between test anxiety, perfectionism and aggressiveness. Statistical analyses have confirmed, in a 3 factor solution, the presence of emotional (anger), cognitive (hostility) and behavioural (physical aggression) components. Internal consistency is satisfactory. It is demonstrated that physical aggression characterizes boys (F=12.04, p=0.0001) while hostility (F=5.22, p=0.0015) and anger (F=0.49, p=0.0001) characterizes girls; furthermore it is noted that physical aggression characterizes more failed students (F=13.43, p=0.0003). Four models (see figures 2, 3, 4, 5) have been established, at first focused on the distinction of correlations between motivation and cognitive and emotional components on the samples of boys (n=268) and girls (348), then developed on the samples of successful students, male (n=193) and female (n=271). They describe the differentiated action of intrinsic and extrinsic motivations on the different components of aggressiveness and test-anxiety according to gender and without experience of failure. The dynamic process of the organizational factors is different according to gender and psychopathology resulting from the combinations of behaviors, cognitions and emotions would be assumed, prioritizing physical aggression and psychopathy by boys, anxiety and depression by girls. Anyway more explanation about the evolution of success rates of boys and girls in Belgian universities is proposed.

Adult↗

Paroxetine binding in aggressive schizophrenic patients.

Decreased central serotonergic activity has been associated with aggressive behavior in humans and animals. Whether or not this phenomenon is related to current aggression or to aggressive tendency is debatable. [3H]paroxetine binding in blood platelets represents the activity of serotonin peripheral binding sites. We investigated a possible association between [3H]paroxetine binding in blood platelets and current aggression or homicidal history in schizophrenic patients. Blood platelets of 11 aggressive schizophrenic patients were assayed for [3H]paroxetine binding in blood platelets and compared to findings in 15 non-aggressive schizophrenic patients, 15 presently non-aggressive schizophrenic patients with homicidal history, and 15 healthy volunteers. Clinical evaluation was performed using the Positive and Negative Syndrome Scale, the Hamilton Rating Scale for Depression and the Clinical Global Impression scale. B(max) of [3H]paroxetine binding in blood platelets of currently aggressive schizophrenic patients was significantly higher than that in platelets of non-aggressive schizophrenic patients, presently non-aggressive patients with homicidal history and healthy volunteers. No difference was found between the last three study groups. No significant correlation was found between scores of all rating scales and the investigated biochemical parameters. An association was found between current aggression among schizophrenic patients and high B(max) values of [3H]paroxetine binding in blood platelets. This association is probably related to present state of aggression rather than to tendency towards aggression.

Adult↗

Impulsive and premeditated aggression: a factor analysis of self-reported acts.

Although aggression research in general has been hampered by a lack of objective measurements of aggressive acts, two types of aggressive acts, impulsive vs. premeditated, have been studied extensively in recent years. These two types of aggression have been primarily measured by structured or semi-structured interviews. The current study was designed to assess the construct validity of these two types of aggression using a self-report questionnaire which included items gleaned from the content of interviews used in past studies. For this study, 216 college students assessed their own aggressive acts rather than answering general questions about aggression. The students were not significantly different from normative sample groups on self-report measures of impulsiveness, aggression, and anger/hostility. A PCA factor analysis with a promax rotation of the items on the self-report questionnaire identified four factors: impulsive aggression; mood on the day the act occurred; premeditated aggression; and agitation. Thus, impulsive and premeditated aggression are independent constructs which exist in varying degrees among these 'normal' persons in a non-clinical sample. Impulsive aggression was characterized in part by feelings of remorse following the acts and by thought confusion. Premeditated aggression was related to social gain and dominance.

Adult↗

Aggressive behaviour at first contact with services: findings from the AESOP First Episode Psychosis Study.

BACKGROUND: Aggressive behaviour is increased among those with schizophrenia but less is known about those with affective psychoses. Similarly, little is known about aggressive behaviour occurring at the onset of illness. METHOD: The main reasons for presentation to services were examined among those recruited to a UK-based first episode psychosis study. The proportion of individuals presenting with aggressive behaviour was determined and these individuals were compared to those who were not aggressive on a range of variables including sociodemographic, clinical, criminal history, service contact, and symptom characteristics. Among the aggressive group, those who were physically violent were distinguished from those who were not violent but who were still perceived to present a risk of violence to others. RESULTS: Almost 40% (n=194) of the sample were aggressive at first contact with services; approximately half of these were physically violent (n=103). Younger age, African-Caribbean ethnicity and a history of previous violent offending were independently associated with aggression. Aggressive behaviour was associated with a diagnosis of mania and individual manic symptoms were also associated with aggression both for the whole sample and for those with schizophrenia. Factors differentiating violent from non-violent aggressive patients included male gender, lower social class and past violent offending. CONCLUSIONS: Aggressive behaviour is not an uncommon feature in those presenting with first episode psychosis. Sociodemographic and past offending factors are associated with aggression and further differentiate those presenting with more serious violence. A diagnosis of mania and the presence of manic symptoms are associated with aggression.

Adolescent↗

Victim reactions in aggressive erotic films as a factor in violence against women.

The present study was designed to investigate whether the behavioral characteristics of the people in erotic films and the nature of the targets available for aggression afterward can affect subsequent aggression. In Experiment 1, male subjects were angered by a male or female confederate. They were then shown a neutral film or one of three erotic films. The erotic films differed in terms of their aggressive content (two were aggressive and one was nonaggressive) and the reactions of the female victim in the two aggressive films (positive vs. negative). Subjects were then allowed to aggress against the confederate via electric shock. Results indicated that films had no effect on male targets whereas both types of aggressive erotic films increased aggression toward the female. In Experiment 2, the effects of the above films on nonangry viewers were investigated with only female confederates. Results indicated that angered male subjects were more aggressive toward the female after viewing either aggressive erotic film but that only the positive-outcome aggressive film increased aggression in nonangered subjects. Both the theoretical and applied aspects of aggressive and nonaggressive erotica are discussed.

Aggression↗

Psychopharmacological treatment of aggression in schizophrenic patients.

Aggressive behavior is frequently observed in schizophrenic patients. More than 50 % of all psychiatric patients and 10 % of schizophrenic patients show aggressive symptoms varying from threatening behavior and agitation to assault. The pharmacological treatment of acute, persisting and repetitive aggression is a serious problem for other patients and staff members. Not only is violent behavior from mentally ill patients the most detrimental factor in their stigmatization, aggression is also a considerable direct source of danger for the patients themselves. Based on rather limited evidence, a wide variety of medications for the pharmacological treatment of aggression has been recommended: typical and atypical antipsychotics, benzodiazepines, mood stabilizers, beta-blockers and selective serotonin reuptake inhibitors (SSRIs). Most clinical information on treating aggression has been collected for atypical neuroleptics, particularly for clozapine. Several retrospective and open studies indicate its efficacy. Treatment duration of 6 months is recommended to induce a stable reduction of physical and verbal aggression. Severe side effects have very rarely been seen. At the moment, clozapine seems to be the first choice in aggression treatment. Within the last few years, about 10 articles were published showing that this is the most effective antiaggressive agent in the treatment of aggression and agitation in psychiatric patients, independent of psychiatric diagnosis. However, clozapine, like all the other substances used, does not have an established indication for the treatment of aggressive symptoms. Noncompliance with medication makes it difficult to choose the right preparation for the medication: tablets, liquids, intramuscular injections and readily soluble "FDDFs" are available. Ethical, juridical and methodological problems prevent controlled studies from establishing a reference in the treatment of aggression in mentally ill patients. This review summarizes the current discussion and publications on the pharmacological treatment of aggression in schizophrenic patients of the last 20 years. In addition, we will briefly present studies and case reports concerning the treatment of aggression in other psychiatric patients.

Adrenergic beta-Antagonists↗

Prevalence and precipitants of aggression in psychiatric inpatient units.

OBJECTIVE: Aggression is a significant clinical problem in psychiatric facilities. The present study reviews data on aggression collected from psychiatric inpatient units in order to determine prevalence and causal factors. METHOD: Data on aggressive incidents were gathered from four adult psychiatric units in the Illawarra, Australia. Information obtained included diagnosis, causal factors and patient sociodemographic characteristics. RESULTS: During the 18-month period, a total of 1269 psychiatric patients were admitted and 174 patients (13.7%) were recorded as being aggressive. Patients with bipolar affective disorder and schizophrenia had a 2.81 and 1.96 significantly increased risk of aggression, respectively, while depression and adjustment disorder conferred a significantly lower risk. Aggression was most likely to occur within 2 days of admission and length of stay was greater for aggressive than non-aggressive patients. The greater number of incidents occurred on day shift. Most patients who displayed aggression did so on one occasion, but a small proportion of total patients (6.0%) accounted for a large number of incidents (71.0%). High-risk patients were identified as those who were under 32 years of age, were actively psychotic, detained and known to have a history of aggression and substance misuse. The most frequent form of aggression was physical and staff were most often the victims. CONCLUSIONS: These results have important implications for predicting and thereby reducing inpatient aggression. Organisations need to ensure aggression management strategies are in place and periodically identify and assess the level of risk for workers.

Adolescent↗

Serotonin, aggression, and parental psychopathology in children with attention-deficit hyperactivity disorder.

OBJECTIVE: To explore the relationship between central serotonergic (5-HT) function and history of parental aggression in aggressive and nonaggressive boys with attention-deficit hyperactivity disorder (ADHD). METHOD: History of psychiatric symptoms was assessed in the biological parents of 41 boys with ADHD. The relationship between 5-HT function in aggressive and nonaggressive probands, as assessed via the prolactin response to fenfluramine (FEN) challenge, and parental history of aggression was examined. RESULTS: Aggressive boys with a parental history of aggressive behavior had a significantly lower prolactin response to FEN challenge than aggressive boys without a parental history of aggression. Nonaggressive boys had a prolactin response midway between those of the two aggressive subgroups, and their prolactin response did not vary as a function of parental aggression. Children subdivided on the basis of parental history of other psychiatric symptoms did not differ in their response to the FEN challenge. CONCLUSIONS: These data indicate an association between parent aggressive behavior and lower 5-HT function in aggressive boys with ADHD but do not indicate the extent to which this association is environmentally and/or genetically transmitted. There may be different neurochemical mechanisms in familial and nonfamilial aggressive children, which have clinical implications for pharmacological interventions.

Adult↗

Response decision processes in relational and overt aggression.

Response decision processes of relationally and overtly aggressive children were assessed for both boys and girls. A hypothetical-situation instrument, adapted from past research, was used to assess children's evaluations of relationally aggressive and overtly aggressive responses to both relational and instrumental conflict situations for third-through sixth-grade children (n = 1,166). Findings revealed that both overtly aggressive boys and overtly aggressive girls evaluated overtly aggressive responses to instrumental conflict situations in relatively positive ways. Further, overtly aggressive girls, but not boys, evaluated overtly aggressive responses to relational conflict situations in relatively positive ways. Additionally, relationally aggressive boys evaluated relationally aggressive responses to instrumental conflict situations in relatively positive ways. Gender differences were also obtained. Boys evaluated overt aggression more positively, whereas girls evaluated relational aggression more positively. Implications of these findings for the role of gender, situation type, response type, and aggression type for our understanding of children's social information processing are discussed.

Aggression↗

Effects of drugs on behaviour of aggressive mice.

1 The occurrence of 11 aggressive and non-aggressive activities was observed in aggressive male mice treated with drugs in paired interactions with non-aggressive males given water. Effects of chlordiazepoxide, diazepam, barbitone, chlorpromazine, imipramine, (+)-amphetamine, lysergic acid diethylamide (LSD) all given orally and of intraperitoneal scopolamine were investigated.2 Scopolamine (0.25 and 0.75 mg/kg), (+)-amphetamine (0.25 and 1 mg/kg), chlorpromazine (2.5 mg/kg), diazepam (10 mg/kg) and chlordiazepoxide (50 mg/kg) reduced aggressive activities (attacks, aggressive unrest) without inhibiting walking across the cage or rearing in the aggressive mice. Thus, the inhibition of aggression induced by these drugs does not seem to be due to neuromuscular impairment and seems to this extent specific. On the other hand, imipramine lessened aggressive activities only at a dose (80 mg/kg) which also decreased walking across the cage and rearing. Barbitone or LSD did not change aggression at either dose tested (20 and 60 or 0.01 and 1 mg/kg, respectively). Aggressive activities were increased significantly only by chlordiazepoxide at a dose of 5 mg/kg.3 (+)-Amphetamine (0.25 mg/kg) and scopolamine (0.75 mg/kg) increased escapes and alert postures, respectively, in the aggressive mice.4 Diazepam and chlordiazepoxide decreased tail rattling at 1 and 5 mg/kg, respectively, doses 10 times lower than those inhibiting attacks. The other drugs tested inhibited tail rattling only at doses reducing attacks. Tail rattling appears to be a convenient measure for testing effects of drugs on behavioural conflict.5 Diazepam (5 and 10 mg/kg), chlordiazepoxide (20 and 50 mg/kg), barbitone (60 mg/kg) and scopolamine (0.25 and 0.75 mg/kg) increased sociable activities (sniffing, following partners and climbing over them) whereas (+)-amphetamine, chlorpromazine, imipramine and LSD did not. Effects of the drugs on sociable activities in aggressive mice seem to correlate with their action on punished responding and other types of suppressed behaviour.

Aggression↗

Genetic contributions to subtypes of aggression.

Boys and girls may display different styles of aggression. The aim of this study was to identify subtypes of aggression within the Child Behavior Checklist (CBCL) aggression scale, and determine their characteristics for both sexes. Maternal CBCL ratings of 7449 7-year-old twin pairs were analyzed using principal components analyses to identify subtypes of aggression, and structural equation modeling to carry out genetic analyses. Two aggression subtypes were identified: relational and direct aggression. The correlation between these subtypes was .58 for boys and .47 for girls. Boys had higher mean scores for both subtypes of aggression, but sex differences were largest for direct aggression. For relational aggression, 66% of the variance was due to additive genetic influences, 16% to shared environment and 18% to nonshared environment. For direct aggression, additive genetic effects accounted for 53% of the variance in males and 60% in females, shared environment explained 23% of the variance in males and 13% in females, and nonshared environmental effects explained 24% of the variance in males and 27% in females. Covariance between the aggression subtypes was mostly accounted for by additive genetic (55% for boys, 58% for girls) and shared environmental influences (33% for boys, 30% for girls). Direct and relational aggression were both influenced by one underlying set of shared environmental factors, but only partly by the same genes (the genetic correlation was .54 for boys and .43 for girls). These findings may have implications for how aggressive behavior should be assessed in boys and girls.

Aggression↗