Sensorimotor Gating in Cocaine-Related Disorder with Comorbid Schizophrenia or Antisocial Personality Disorder

Aggressive behaviour in antipsychotic-naive first-episode schizophrenia patients, their unaffected siblings and healthy controls

AIM

While patients with schizophrenia are more likely to be victims rather than perpetrators of aggressive behaviour, prior research has shown increased rates of aggressive behaviours in these patients that appear very early in the course of illness. We aimed to assess aggression in antipsychotic-naive first-episode schizophrenia patients, their healthy siblings, and controls; and to investigate correlates of aggression in the patients group.

METHODS

Patients (N = 55), siblings (N = 55) and healthy controls (N = 71) were evaluated on Buss and Perry Aggression Questionnaire (AQ), Life History of Aggression (LHA), Barratt Impulsiveness Scale, and Levenson Self-Report Psychopathy Scale. Age, gender and substance use were regarded as covariates, and differences between the three groups were evaluated using analysis of covariance. Hierarchical regression was performed to determine which variables were associated with aggression level in the patients group.

RESULTS

The Tukey multiple comparison test showed that both patients (p < .001) and siblings (p = .023) scored higher on the LHA Aggression than controls. Siblings scored higher than controls (p = .010) for the Anger subscale of the AQ. Patients scored significantly higher than controls in the three impulsiveness dimensions; whereas siblings scored higher than controls in the motor (p = .023) and non-planning (p = .004) dimensions. Multivariate analyses showed that, after controlling for confounders, only attentional impulsiveness (β = .446, p = .0244) and psychopathy traits (β = .359, p = .010) helped predict AQ total scores among patients.

CONCLUSION

Aggression and some of its risk factors including impulsiveness are likely to be trait variables that might provide important vulnerability markers for people at heightened risk of developing psychosis.

Cocaine Increases Sensorimotor Gating and is Related to Psychopathy

OBJECTIVE

Prepulse inhibition regulates sensorimotor gating and is a marker of vulnerability to certain disorders. We compared prepulse inhibition, psychopathy, and sensitivity to punishment and reward in patients with cocaine-related disorder without psychiatric comorbidities and a control group.

METHODS

This was an observational study of a sample of 22 male cases with cocaine-related disorder and 22 healthy male controls. We used the Psychiatric Research Interview for Substance and Mental Disorders and Mini International Neuropsychiatric Interview; the Sensitivity to Punishment and Sensitivity to Reward Questionnaire; and the Levenson Self-Report Psychopathy Scale and Hare Psychopathy Checklist-Revised. Prepulse inhibition was evaluated at 30, 60, and 120 ms.

RESULTS

Cocaine-related disorder group had a higher overall score (t = 12.556, p = .001) and primary psychopathy score (t = 3.750, p = .001) on Levenson Self-Report Psychopathy Scale, a higher score on both Hare Psychopathy Checklist-Revised factors, sensitivity to rewards (t = 3.076, p = .005) and prepulse inhibition at 30 ms (t = 2.859, p = .008).

CONCLUSIONS

Cocaine use in patients without psychiatric comorbidities seems to increase sensorimotor gating. Therefore, these patients likely have an increased sensitivity to rewards, causing them to focus more on cocaine-boosting stimuli, thus explaining the psychopathic traits of these individuals.

Prepulse Inhibition in Cocaine Addiction and Dual Pathologies

Cocaine addiction is frequently associated with different psychiatric disorders, especially schizophrenia and antisocial personality disorder. A small number of studies have used prepulse inhibition (PPI) as a discriminating factor between these disorders. This work evaluated PPI and the phenotype of patients with cocaine-related disorder (CRD) who presented a dual diagnosis of schizophrenia or antisocial personality disorder. A total of 74 men aged 18–60 years were recruited for this research. The sample was divided into four groups: CRD (n = 14), CRD and schizophrenia (n = 21), CRD and antisocial personality disorder (n = 16), and a control group (n = 23). We evaluated the PPI and other possible vulnerability factors in these patients by using different assessment scales. PPI was higher in the CRD group at 30 ms (F(3, 64) = 2.972, p = 0.038). Three discriminant functions were obtained which allowed us to use the overall Hare Psychopathy Checklist Revised score, reward sensitivity, and PPI at 30 ms to predict inclusion of these patients in the different groups with a success rate of 79.7% (42.9% for CRD, 76.2% for CRD and schizophrenia, 100% for CRD and antisocial personality disorder, and 91.3% in the control group). Despite the differences we observed in PPI, this factor is of little use for discriminating between the different diagnostic groups and it acts more as a non-specific endophenotype in certain mental disorders, such as in patients with a dual diagnosis.