Cerebrospinal fluid GABA concentration: relationship with impulsivity and history of suicidal behavior, but not aggression, in human subjects

The objective of this study was to assess the relationship between cerebrospinal fluid concentrations of the neurotransmitter gamma-aminobutyric acid (GABA) and measures of impulsivity and related behaviors (aggression and suicidality) in healthy volunteer and personality disordered subjects. CSF GABA levels, and measures of impulsivity, aggression, and history of suicidal behavior were obtained by morning lumbar puncture in 57 healthy volunteer subjects and in subjects with personality disorder. CSF GABA levels were not found to correlate with measures of aggression but were found to correlate directly with measures of impulsivity; e.g., a composite measure of impulsivity in all subjects (r = 0.35, df = 46, P = 0.015) and in personality disordered subjects examined separately (r = 0.39, df = 30, P = 0.029). In the personality disorder group, CSF GABA levels were higher among subjects with a history of suicidal behavior compared with those without this history. These data suggest that central GABAergic function correlates directly with impulsiveness and history of suicidal behavior, but not aggressiveness, in personality disordered subjects. This may be consistent with observations that high doses of benzodiazepines can lead to “behavioral disinhibition” in human subjects. Further work assessing this and other aspects of the central GABA system in personality disordered subjects are warranted.     

Inter-relationship between different platelet measures of 5-HT and their relationship to aggression in human subjects

The objective of this study was to explore the inter-relationship of three platelet measures of serotonergic function (5-HT): 5-HT Transporter Binding, 5-HT-2 Receptor Binding and 5-HT Content and to explore their inter-relationship with measures of aggression and impulsivity. 58 male subjects with personality disorder were studied. Numbers of platelet 5-HT Transporter and 5-HT-2 Receptor sites were assessed by examining the Bmax of ³H-Paroxetine Binding and the Bmax of ¹²⁵I-LSD Binding to the blood platelet; 5-HT Content was assessed by measuring the amount of 5-HT in the platelet material. Life history of aggression was assessed by Life History of Aggression. Impulsivity was assessed by the Impulsivity Scale of the Eysenck Personality Questionnaire-II. Platelet 5-HT Transporter Binding correlated with both 5-HT-2 Receptor Binding and 5-HT Content; the latter two variables did not correlate with each other. Only Platelet 5-HT Transporter binding correlated significantly with LHA Aggression. These data suggest that while Platelet 5-HT Transporter binding correlates with both 5-HT-2 Receptor Binding and with 5-HT Content, that only 5-HT Transporter Binding represents a correlate of aggression in male personality disordered subjects.     

Cerebrospinal fluid 5-hydroxyindolacetic acid and homovanillic acid: reciprocal relationships with impulsive aggression in human subjects

While the relationship between cerebrospinal fluid 5-HIAA (CSF 5-HIAA) and aggression is typically reported as inverse, studies of some groups of aggressive individuals demonstrate a positive (or no) relationship, between these two variables. It is possible that simultaneous examination of both CSF 5-HIAA and CSF homovanillic acid (HVA), which co-vary in human subjects may clarify differences in reported findings in different groups of aggressive individuals. CSF 5-HIAA and CSF HVA concentrations were simultaneously examined in 60 healthy human subjects (40 with personality disorder and 20 healthy controls) and were correlated with measures of aggression and impulsivity. CSF 5-HIAA concentrations correlated positively, and CSF HVA concentrations correlated inversely, with a composite measure of impulsive aggression in all subjects as well as in the personality disordered subjects. The CSF 5-HIAA findings are consistent with those demonstrating reduced post-synaptic 5-HT receptor responsiveness to 5-HT agent challenge and suggest differences in the pathophysiology between different groups of subjects with aggressive behavior, particularly with regard to severity of aggressive behavior.     

Serotonergic responsivity and behavioral dimensions in antisocial personality disorder with substance abuse

In order to assess the possibility of altered serotonergic responsivity in antisocial personality disorder with substance abuse (ASP), 15 men with ASP and 12 controls were challenged with the serotonin agonist, m-chlorophenylpiperazine (m-CPP), and prolactin and cortisol responses were evaluated. Psychometric measures of hostility and aggression, impulsivity, cognitive tempo, and various aspects of sociopathy were also obtained. ASP subjects had a significantly reduced prolactin response to m-CPP compared with controls, and a significantly greater cortisol response. The prolactin responses showed a significant inverse correlation with measures of assaultive aggression, hypophoria (negative affects), and increased needs. There was no significant correlation found between cortisol responses and any of the psychometric measures. Impulsivity as characterized either by behavioral self-report or measurement of cognitive tempo did not correlate with either prolactin or cortisol responses. A discriminant function analysis depicted ASP subjects as displaying resentment towards others and having poor test-taking efficiency, heightened irritability, and diminished prolactin response to m-CPP. Using these four criteria, nearly 93% of subjects were successfully classified. These results suggest that altered serotonergic function is associated with assaultiveness and dysphoria but not impulsivity in individuals with ASP.     

Impulsivity,gender, and response to fenfluramine challenge in borderline personality disorder

Behavioral impulsivity in borderline personality disorder (BPD) is associated with indices of diminished central serotonergic function, independent of suicidal behavior, depression or alcohol use disorder. Many of these studies have been conducted among males in specialized settings. Studies of BPD females, who constitute the majority of BPD patients, are generally conducted in community settings and report inconsistent findings. We studied gender differences in behavioral impulsivity and the prolactin response to D,L-fenfluramine (FEN) in BPD subjects in a community setting. A FEN challenge study was conducted with 64 BPD subjects (20 male, 44 female), and 57 controls (36 male, 21 female). Axis I and II disorders, including BPD, and suicidal histories were assessed by structured interviews. Controls were free of Axis I and II disorders. Impulsivity and aggression were assessed by the Buss-Durkee Hostility Inventory, Barratt Impulsiveness Scale, Minnesota Multiphasic Personality Inventory-Psychopathic Deviate subscale, and the Brown-Goodwin Lifetime History of Aggression. Male, but not female, BPD subjects had significantly diminished prolactin responses compared to controls. Impulsivity and aggression each predicted prolactin responses. A significant effect of BPD diagnosis on prolactin response was eliminated when impulsivity was co-varied. Impulsivity and aggression were inversely related to delta-prolactin and peak-prolactin responses among male but not female subjects. Gender differences in central serotonergic function may contribute to variations in impulsivity in BPD.     

Self-mutilation in personality disorders: psychological and biological correlates.

OBJECTIVE: The goal of this study was to determine whether self-mutilators with personality disorders differ from nonmutilators with personality disorders in impulsivity, aggression, and other psychopathology and whether serotonergic dysfunction contributes to self-mutilation. METHOD: Twenty-six self-mutilators with personality disorders were matched to 26 control subjects with personality disorders for gender, age, education, axis I diagnosis of affective disorder, and axis II diagnosis of personality disorder. Numerous indexes of psychopathology as well as CSF 5-hydroxyindoleacetic acid (5-HIAA) levels and platelet imipramine binding sites (Bmax) and affinity (Kd) were determined. RESULTS: Self-mutilators had significantly more severe character pathology, had greater lifetime aggression, and were more antisocial than the control subjects. The self-mutilators scored higher on the Hamilton Rating Scale for Depression but not on the Beck Depression Inventory or the Beck Hopelessness Scale. The two groups did not differ on the Buss-Durkee Hostility and Guilt Inventory or on the Sensation Seeking Scale. The degree of self-mutilation was significantly correlated with impulsivity, chronic anger, and somatic anxiety. Both self-mutilation and impulsivity showed significant negative correlations with Bmax, although the two groups did not differ in CSF 5-HIAA levels or in platelet imipramine binding. CONCLUSIONS: The results demonstrate the contribution of severe character pathology, aggression, impulsivity, anxiety, and anger to self-mutilation and provide preliminary support for the hypothesis of underlying serotonergic dysfunction facilitating self-mutilation.     

Personality and attempted suicide. Analysis of anger, aggression and impulsivity

Suicide is one of the leading causes of death worldwide, mortality from suicide being approximately 2%. Attempted suicide appears to be a major risk factor for suicide completion. Anger, aggression and impulsivity are personality traits associated with suicide attempt. In this study we analysed a part of a previously reported sample in order to test anger, impulsivity and temperament/character scales as predictors of aggression and self-aggression in suicide attempters and to compare anger- and aggression-related traits between impulsive and premeditated suicide attempts as well as between violent and non-violent suicide methods.One-hundred-eleven consecutively admitted inpatients with a lifetime history of attempted suicide were assessed for anger (State-Trait Anger Expression Inventory, STAXI), aggression (Questionnaire for Measuring Factors of Aggression, FAF) and temperament/character (Temperament and Character Inventory, TCI).Higher aggression scores, as measured by FAF, were predicted by being male, meeting criteria for borderline personality disorder and having higher angry temperament scores as assessed by STAXI; low cooperativeness was also associated with aggression but not after controlling for STAXI scales. TCI dimensions associated with self-aggression were high harm avoidance, high impulsivity and low self-directedness; state anger, inwardly directed anger and inhibition of aggression were also predictors of self-aggression.In conclusion, impulsivity and harm avoidance have emerged as temperament dimensions independently associated with self-aggressive tendencies in personality. Such interactions could explain the correlation between temperament and suicidality but further research is needed. Anger and self-directedness appear to have some effects on suicide attempt.     

Evaluation of behavioral impulsivity and aggression tasks as endophenotypes for borderline personality disorder

Borderline personality disorder (BPD) is marked by aggression and impulsive, often self-destructive behavior. Despite the severe risks associated with BPD, relatively little is known about the disorder’s etiology. Identification of genetic correlates (endophenotypes) of BPD would improve the prospects of targeted interventions for more homogeneous subsets of borderline patients characterized by specific genetic vulnerabilities. The current study evaluated behavioral measures of aggression and impulsivity as potential endophenotypes for BPD. Subjects with BPD (N = 127), a non cluster B personality disorder (OPD N = 122), or healthy volunteers (HV N = 112) completed self report and behavioral measures of aggression, motor impulsivity and cognitive impulsivity. Results showed that BPD subjects demonstrated more aggression and motor impulsivity than HV (but not OPD) subjects on behavioral tasks. In contrast, BPD subjects self-reported more impulsivity and aggression than either comparison group. Subsequent analyses showed that among BPD subjects behavioral aggression was associated with self-reported aggression, while behavioral and self-report impulsivity measures were more modestly associated. Overall, the results provide partial support for the use of behavioral measures of aggression and motor impulsivity as endophenotypes for BPD, with stronger support for behavioral aggression measures as an endophenotype for aggression within BPD samples.     

SSRI treatment of borderline personality disorder: a randomized,placebo-controlled clinical trial for female patients with borderline personality disorder

OBJECTIVE: Selective serotonin reuptake inhibitors (SSRIs) are recommended for treatment of affect lability, impulsivity, and aggression in patients with borderline personality disorder. This recommendation is based on positive findings in at least 10 open studies and one small double-blind study of SSRIs for patients with borderline personality disorder and one study of impulsive aggressive patients with different personality disorders. A randomized, placebo-controlled SSRI study with borderline personality disorder patients, however, provided inconclusive results because of a large response to placebo. It was, therefore, decided to conduct a new randomized trial with a larger study group. METHOD: A double-blind, placebo-controlled, randomized trial using the SSRI fluvoxamine for 6 weeks followed by a blind half-crossover for 6 weeks and an open follow-up for another 12 weeks was conducted with 38 nonschizophrenic, nonbipolar female patients with borderline personality disorder. The outcome measures were the rapid mood shift, impulsivity, and aggression subscales from the Borderline Personality Disorder Severity Index. RESULTS: Fluvoxamine but not placebo produced a robust and long-lasting reduction in the scores on the subscale for rapid mood shifts. In contrast, no difference between the fluvoxamine and placebo groups was observed in the effect on the impulsivity and aggression scores. CONCLUSIONS: In this study, fluvoxamine significantly improved rapid mood shifts in female borderline patients, but not impulsivity and aggression. This latter finding may be due to gender-specific differences in impulsivity and aggression.     

Cortisol responses to ipsapirone challenge correlate with aggression, while basal cortisol levels correlate with impulsivity, in personality disorder and healthy volunteer subjects

Background

This study was performed to test the hypothesis that 5-HT-1a receptors, as assessed by the cortisol (post-synaptic) and temperature (pre-synaptic) responses to the 5-HT-1a agonist, Ipsapirone (IPSAP), play a role in the regulation of impulsive aggressive behavior in human subjects.

Methods

Fifty-two healthy subjects (28 with Personality Disorder: PD; 24 Healthy Volunteers: HV) underwent acute challenge with the selective 5-HT-1a agonist, ipsaprione (IPSAP: .3 mg/kg po). Residual Peak Delta Cortisol (ΔCORT[IPSAP]-R; after removal of Basal CORT and IPSAP plasma levels) was used as the primary 5-HT-1a post-synaptic receptor variable. Residual Nadir Delta Temperature (ΔTEMP[IPSAP]-R; after removal of Basal TEMP) was used as the primary 5-HT-1a somatodendritic (pre-synaptic) receptor variable. Measures of trait aggression included the Aggression scales of the Buss-Durkee Hostility Inventory (BDHI) and the Life History of Aggression (LHA); trait impulsivity was assessed with the Impulsivity scale of the Eysenck Personality Questionnaire (EPQ-II).

Results

Correlations between ΔCORT[IPSAP]-R responses and BDHI Aggression scores varied by group. Specifically, BDHI Aggression correlated inversely with ΔCORT[IPSAP]-R values in PD subjects but directly in HV subjects. While EPQ-II Impulsivity did not correlate with ΔCORT[IPSAP]-R responses, this measure of impulsivity correlated directly with Basal CORT levels in all subjects. ΔTEMP[IPSAP]-R responses did not correlate with measures of trait aggression or trait impulsivity.

Conclusion

Physiologic responses of 5-HT-1a post-synaptic receptors may be reduced as a function of trait aggression, but not impulsivity, in PD subjects. In contrast, pre-synaptic 5-HT-1a receptors may not play a role in the regulation of aggression or impulsivity in human subjects.     

CSF 5-HIAA levels are lower in impulsive as compared to nonimpulsive violent suicide attempters and control subjects.

BACKGROUND: We studied CSF 5-HIAA and HVA concentrations in violent suicide attempters and examined their relationship with depression, anxiety, and impulsivity. METHODS: CSF 5-HIAA and HVA concentrations were determined very shortly after hospital admission and compared to those of a matched control population. Clinical evaluation was performed concomitantly; the level impulsivity was evaluated by the Impulsivity Rating Scale (IRS). RESULTS: Twenty-three patients and 23 control subjects were included. According to the IRS, 14 patients were classified as impulsive, including all patients suffering from personality disorders, and 9 as nonimpulsive, with a main DSM-IIIR diagnosis of melancholia. CSF 5-HIAA concentrations in the suicide group were significantly lower than in control subjects. This difference was entirely due to the impulsive suicide attempters. There was an inverse correlation between the IRS score and CSF 5-HIAA (r = -.47, p = .02) and only a trend for HVA (r = -.41, p = .078) levels in the suicide group. CONCLUSIONS: This study of a group of violent suicide attempters distinguished a subgroup of patients diagnosed with personality disorder with high impulsivity scores and a subgroup of patients with the main diagnosis of severe depression. CSF 5-HIAA was significantly lower in impulsive violent attempters than in nonimpulsive violent attempters, therefore desintangling violence from impulsivity and linking this biologic abnormality to impulsivity.     

Growth hormone responses to intravenous clonidine challenge correlate with behavioral irritability in psychiatric patients and healthy volunteers.

To explore the relationship between central noradrenergic receptor responsivity and indices of impulsive aggression, growth hormone responses to infusions with the alpha 2-adrenergic receptor agonist clonidine (GH[CLON]) and responses on the Buss-Durkee Hostility Inventory (BDHI) were examined in healthy male volunteers and male patients with major affective or personality disorder. GH[CLON] values were found to correlate significantly with the BDHI "Irritability" subscale in all subjects, but especially in healthy volunteer and personality disorder patients. GH[CLON] values did not correlate with the BDHI "Assault" subscale. These results suggest a role for central alpha 2-adrenergic receptor responsivity in the personality trait characterized by behavioral irritability, but not overt assaultiveness, in humans.     

Dopamine D2/D3 receptor availability and venturesomeness

The construct of impulsivity is considered as a major trait of personality. There is growing evidence that the mesolimbic dopamine system plays an important role in the modulation of impulsivity and venturesomeness, the two key components within the impulsivity-construct. The aim of the present study was to explore an association between trait impulsivity measured with self-assessment and the dopaminergic neurotransmission as measured by positron emission tomography (PET) in a cohort of healthy male subjects. In vivo D2/D3 receptor availability was determined with [¹⁸F]fallypride PET in 18 non-smoking healthy subjects. The character trait impulsivity was measured using the Impulsiveness-Venturesomeness-Empathy questionnaire (I7). Image processing and statistical analysis was performed on a voxel-by-voxel basis using statistical parametric mapping (SPM) software. The I7 subscale venturesomeness correlated positively with the D2/D3 receptor availability within the left temporal cortex and the thalamus. Measures on the I7 subscale impulsiveness and empathy did not correlate with the D2/D3 receptor availability in any brain region investigated. Our results suggest the involvement of extrastriatal dopaminergic neurotransmission in venturesomeness, a component of impulsivity.     

Borderline personality disorder, impulsivity, and the orbitofrontal cortex

OBJECTIVE: Orbitofrontal cortex lesions produce disinhibited or socially inappropriate behavior and emotional irregularities. Characteristics of borderline personality disorder include impulsivity and affective instability. The authors investigated whether aspects of borderline personality disorder, in particular impulsivity, are associated with orbitofrontal cortex dysfunction. METHOD: Measures of personality, emotion, impulsivity, time perception, sensitivity to reinforcers, and spatial working memory were administered to patients with borderline personality disorder (N=19), patients with orbitofrontal cortex lesions (N=23), patients with lesions in the prefrontal cortex but not in the orbitofrontal cortex (N=20), and healthy comparison subjects (N=39). RESULTS: The patients with orbitofrontal cortex lesions and the patients with borderline personality disorder performed similarly on several measures. Both groups were more impulsive and reported more inappropriate behaviors, borderline personality disorder characteristics, and anger and less happiness than the two comparison groups, and both groups were less open to experience and had a faster perception of time (underproduced time) than the healthy comparison subjects. The patients with orbitofrontal cortex lesions and the borderline personality disorder patients performed differently on other measures. The borderline personality disorder patients were less extraverted and conscientious and more neurotic and emotional than all other groups. Patients with orbitofrontal cortex lesions had deficits in reversing stimulus-reinforcer associations and a faster perception of time (overestimated time) than the healthy comparison subjects. CONCLUSIONS: Orbitofrontal cortex dysfunction may contribute to some core characteristics of borderline personality disorder, in particular impulsivity. Other characteristics of borderline personality disorder, such as high levels of emotionality and personality irregularities, do not appear to be related to the type of dysfunction produced by orbitofrontal cortex damage. The similarities and differences found between the borderline personality disorder patients and the patients with orbitofrontal cortex lesions may lead to a better understanding of the etiology of borderline personality disorder and the functions of the orbitofrontal cortex.     

Relationship of temperament and behaviour measures to the prolactin response to fenfluramine in depressed men

Low central nervous systems (CNS) serotonin has been linked to aggression, impulsivity and disinhibition in both animal and human studies. Low cerebrospinal fluid (CSF) 5-hydroxindoleacetic acid (5HIAA) has been reported in violent criminals, arsonists and violent suicide attempters. Reduced prolactin response to fenfluramine has been found in aggressive patients and criminal offenders. Cloninger's dimension of harm avoidance is hypothesised to be related to CNS serotonin levels, but studies have reported contradictory results. Forty-eight men with major depression received a fenfluramine challenge as well as a number of measures of temperament and behaviour: the Tridimensional Personality Questionnaire (TPQ); the Eysenck Personality Questionnaire (EPQ); the Barratt Impulsivity Scale (BIS); the Hopkins Symptom Checklist (SCL-90); and clinician-rated personality disorder symptoms. The prolactin response to fenfluramine was not related to EPQ or TPQ measures except the TPQ dimension of reward dependence and the EPQ Lie scale. The prolactin response to fenfluramine was not related to BIS measures or to SCL-90 measures except the SCL-90 somatization scale. The prolactin response to fenfluramine was not related to personality disorder diagnoses or to a measure of repeated self-harm. Thus, in a sample of moderately depressed male outpatients, there was very little relationship between personality, behavioural measures and the prolactin response to fenfluramine. We suggest that alterations in serotonin functioning, when measured using the prolactin response to fenfluramine, may be more commonly linked to behavioural abnormalities in personality-disordered or criminal samples.     

The relationship of childhood abuse to impulsivity and suicidal behavior in adults with major depression.

OBJECTIVE: This study investigated whether a higher frequency of reported childhood trauma would be found in depressed adults with higher levels of trait impulsivity, aggression, and suicidal behavior. METHOD: In 136 depressed adult inpatients, the authors assessed trait impulsivity, aggression history, and number of lifetime suicide attempts as well as the medical lethality and the intent to die associated with the most lethal attempt. These variables were then compared between those with and those without a reported history of childhood physical or sexual abuse. RESULTS: Subjects who reported an abuse history were more likely to have made a suicide attempt and had significantly higher impulsivity and aggression scores than those who did not report an abuse history. Impulsivity and aggression scores were significantly higher in subjects with a history of at least one suicide attempt. A logistic regression analysis revealed that abuse history remained significantly associated with suicide attempt status after adjustment for impulsivity, aggression history, and presence of borderline personality disorder. Among those who attempted suicide, there were no significant differences in severity of suicidal behavior between those with and without a childhood history of abuse. CONCLUSIONS: Abuse in childhood may constitute an environmental risk factor for the development of trait impulsivity and aggression as well as suicide attempts in depressed adults. Alternatively, impulsivity and aggression may be inherited traits underlying both childhood abuse and suicidal behavior in adulthood disorders. Additional research is needed to estimate the relative contributions of heredity and environmental experience to the development of impulsivity, aggression, and suicidal behavior.     

Serum testosterone levels, mental disorders and criminal behaviour.

OBJECTIVE: Although previous studies have revealed an association between androgens and aggression, there is a lack of knowledge of this issue in different mental disorders. METHOD: The associations between serum testosterone levels and criminal behaviour in different mental disorders were examined using data collected from forensic psychiatric male patients (20 schizophrenics and 42 subjects with personality disorders). RESULTS: Male criminals with personality disorders had significantly higher serum levels of total and free testosterone than criminal schizophrenics. Among schizophrenics, total (P=0.01) and free testosterone (P=0.01) declined significantly more with age compared to healthy controls and patients with personality disorders, and also correlated with duration of neuroleptic drug use (r=-0.60, P=0.000 for total and r=-0.46, P=0.0001 for free testosterone). The recidivists with personality disorder had higher total (P=0.04) and free testosterone (P=0.05) levels than non-recidivists with personality disorder. CONCLUSION: Personality disordered criminals with multiple offences had high serum testosterone levels. The low testosterone concentrations among schizophrenics may be due either to long-term use of neuroleptic agents or to the mental illness itself and its possible inhibition of the pituitary-gonadal axis.     

High interleukin-6 and impulsivity: determining the role of endophenotypes in attempted suicide

The dysregulation of inflammation has been associated with depression and, more recently, with suicidal behaviors. The reports regarding the relationship between interleukin-6 (IL-6) and suicide attempts are inconsistent. Personality traits such as impulsivity and aggression are considered endophenotypes and important factors that underlie suicidal behaviors. The aim of the current study was to assess whether plasma and cerebrospinal fluid (CSF) levels of IL-6 are associated with personality traits among suicide attempters. We assessed the relationships among personality traits, IL-6 and violent suicide attempts. The plasma and CSF levels of IL-6 were measured in suicide attempters (plasma=58, CSF=39) using antibody-based immunoassay systems. Personality domains were assessed using the Karolinska Scale of Personality (KSP). IL-6 levels in plasma and CSF were used to predict personality domains via regression models. Plasma IL-6 was significantly and positively correlated with extraversion as well as the KSP subscales impulsivity and monotony avoidance. CSF IL-6 was positively correlated with monotony avoidance. Violent suicide attempts tended to be associated with high plasma IL-6 levels. Plasma and CSF levels of IL-6 were not significantly associated with each other. These results indicate that impulsivity and the choice of a violent suicide attempt method might be related to higher levels of IL-6 in individuals who attempt suicide. The neuroinflammation hypothesis of suicidal behavior on the basis of elevated IL-6 levels might be partly explained by the positive association between IL-6 and impulsivity, which is a key element of the suicidal phenotype.     

Human impulsive aggression: a sleep research perspective

Impulsive aggression is commonly associated with personality disorders, in particular antisocial and borderline personality disorders as well as with conduct disorder and intermittent explosive disorder. The relationship between impulsive aggression and testosterone is well established in many studies. One of the aims of this study was to characterize the relationship between earlier-mentioned different categorical psychiatric diagnosis describing human impulsive aggression and sleep using polysomnography and spectral power analysis. Another aim was to study the relationship between serum testosterone and sleep in persons with severe aggressive behaviour. Subjects for the study were 16 males charged with highly violent offences and ordered for a pretrial forensic psychiatric examination. The antisocials with borderline personality disorder comorbidity had significantly more awakenings and lower sleep efficiency compared with the subjects with only antisocial personality disorder. The subjects with severe conduct disorder in childhood anamnesis had higher amount of S4 sleep and higher relative theta and delta power in this sleep stage compared with males with only mild or moderate conduct disorder. The same kind of sleep architecture was associated with intermittent explosive disorder. In subgroups with higher serum testosterone levels also the amount of S4 sleep and the relative theta and delta power in this sleep stage were increased. The study gives further support to the growing evidence of brain dysfunction predisposing to severe aggressive behaviour and strengthens the view that there are different subpopulations of individuals with antisocial personality varying in impulsiveness. The differences in impulsiveness are reflected in sleep architecture as well.     

Two models of impulsivity: relationship to personality traits and psychopathology.

BACKGROUND: Impulsivity is prominent in psychiatric disorders. Two dominant models of impulsivity are the reward-discounting model, where impulsivity is defined as inability to wait for a larger reward, and the rapid-response model, where impulsivity is defined as responding without adequate assessment of context. We have compared the role of these models of impulsivity in human psychopathology, based on the hypothesis that rapid-response impulsivity would be more strongly related to other aspects of psychopathology and to impulsivity as described by questionnaires.METHODS: We investigated relationships between personality and laboratory measures of impulsivity, and between these measures and clinical characteristics, in parents of adolescent subjects with disruptive behavioral disorders (DBDs) and matched control subjects. Diagnoses were rendered using the Structured Interview for DSM-IV. The Barratt Impulsiveness Scale (BIS) was used as a trait measure of impulsivity. Rapid-response impulsivity was assessed using a form of the Continuous Performance Test, the Immediate Memory-Delayed Memory Task (IMT/DMT). Reward-delay impulsivity was measured using two tasks where subjects could choose between smaller immediate or larger delayed rewards.RESULTS: Rapid-response, but not reward-delay impulsivity, was significantly higher in subjects with lifetime Axis I or Axis II diagnoses. Scores on the BIS were elevated in subjects with Axis I diagnoses and correlated significantly with both rapid-response and reward-delay tests, but more strongly with the former. Multiple regression showed that rapid-response, but not reward-delay performance or intelligence quotient, contributed significantly to BIS scores. Correlations were similar in parents of control subjects and of DBD subjects.CONCLUSIONS: These data suggest that measures of rapid-response impulsivity and of reward-delay impulsivity are both related to impulsivity as a personality characteristic. The relationship appears stronger, however, for rapid-response impulsivity, as measured by the IMT/DMT. Laboratory and personality measures of impulsivity appear to be related to risk of psychopathology.