Controlling test specificity for auditory evoked response detection using a frequency domain bootstrap.

BACKGROUND: Statistical detection methods are routinely used to automate auditory evoked response (AER) detection and assist clinicians with AER measurements. However, many of these methods are built around statistical assumptions that can be violated for AER data, potentially resulting in reduced or unpredictable test performances. This study explores a frequency domain bootstrap (FDB) and some FDB modifications to preserve test performance in serially correlated non-stationary data. METHOD: The FDB aims to generate many surrogate recordings, all with similar serial correlation as the original recording being analysed. Analysing the surrogates with the detection method then gives a distribution of values that can be used for inference. A potential limitation of the conventional FDB is the assumption of stationary data with a smooth power spectral density (PSD) function, which is addressed through two modifications. COMPARISONS WITH EXISTING METHODS: The FDB was compared to a conventional parametric approach and two modified FDB approaches that aim to account for heteroskedasticity and non-smooth PSD functions. Hotelling's T2(HT2) test applied to auditory brainstem responses was the test case. RESULTS: When using conventional HT2, false-positive rates deviated significantly from the nominal alpha-levels due to serial correlation. The false-positive rates of the modified FDB were consistently closer to the nominal alpha-levels, especially when data was strongly heteroskedastic or the underlying PSD function was not smooth due to e.g. power lines noise. CONCLUSION: The FDB and its modifications provide accurate, recording-dependent approximations of null distributions, and an improved control of false-positive rates relative to parametric inference for auditory brainstem response detection.

Risk factors of violent offending in mentally ill prisoners with autism spectrum disorders.

BACKGROUND: Results of research regarding a possible causal relation between autism spectrum disorders (ASDs) and violence are mixed. Several explanations have been proposed. AIMS: To assess prevalence rates of comorbid disorders in a large sample of mentally ill offenders diagnosed with ASD. Offenders with and without comorbid mental disorders were compared on several characteristics. To better understand the relationship between ASD and violent criminal behavior, the predictive value of several proposed risk factors (comorbidity, negative social network/influenceability, and childhood trauma/victimization) on violent offending was investigated. METHOD: Data of 394 male offenders with a diagnosis of ASD were included. Prevalence rates of comorbid mental disorders next to ASD were calculated, and characteristics were compared using chi-square or t-tests. The predictive value of the risk factors was assessed using a binary logistic regression (n = 357). RESULTS: High rates of comorbidity were found (78.9%), specifically for substance use disorders (39.8%), schizophrenia spectrum disorders (31.7%), and neurodevelopmental disorder other than ASD (24.1%). Offenders with and without comorbidity differed significantly in their criminal and mental health care history. Both comorbidity (OR = 1.68; 95% CI 1.27-2.18) and a negative social network/influenceability (OR = 1.49; 95% CI 1.11-1.99) showed to be significant predictors of violent offending within this sample. CONCLUSIONS: The highest rates of comorbid disorders found were disorders that have been previously linked to violent offending, and the risk of violent offending could be unrelated to ASD. However, the role of social functioning indicates a risk specific to the symptoms of ASD.

A group sequential test for ABR detection.

Objective: To detect the auditory brainstem response (ABR) automatically using an innovative sequentially applied Hotelling's T 2 test, with the overall goal of optimising test time whilst controlling the false-positive rate (FPR). Design: The stage-wise critical decision boundaries for accepting or rejecting the null hypothesis were found using a new approach called the Convolutional Group Sequential Test (CGST). Specificity, sensitivity, and test time were evaluated using simulations and subject recorded data. Study sample: Data consists of click-evoked ABR threshold series from 12 normal hearing adults, and recordings of EEG background activity from 17 normal hearing adults. Results: Reductions in mean test time of up to 40-45% were observed for the sequential test, relative to a conventional "single shot" test where the statistical test is applied to the data just once. To obtain these results, it will occasionally be necessary to run the test to a higher number of stimuli, i.e. the maximum test time needs to be increased. Conclusions: The CGST can be used to control the specificity of a sequentially applied ABR detection method. Doing so can reduce test time, relative to the "single shot" test, when considered across a cohort of test subjects.

Objective measures for detecting the auditory brainstem response: comparisons of specificity, sensitivity and detection time.

OBJECTIVE: To evaluate and compare the specificity, sensitivity and detection time of various time-domain and multi-band frequency domain methods when detecting the auditory brainstem response (ABR). DESIGN: Simulations and subject recorded data were used to assess and compare the performance of the Hotelling's T2 test (applied in either time or frequency domain), two versions of the modified q-sample uniform scores test and both the Fsp and Fmp, which were evaluated using both conventional F-distributions with assumed degrees of freedom and a bootstrap approach. STUDY SAMPLE: Data consisted of click-evoked ABRs and recordings of EEG background activity from 12 to 17 normal hearing adults, respectively. RESULTS: An overall advantage in sensitivity and detection time was demonstrated for the Hotelling's T2 test. The false-positive rates (FPRs) of the Fsp and Fmp were also closer to the nominal alpha-level when evaluating statistical significance using the bootstrap approach, as opposed to using conventional F-distributions. The FPRs of the remaining methods were slightly higher than expected. CONCLUSIONS: In this work, Hotelling's T2 outperformed the alternative methods for automatically detecting ABRs. Its promise as a sensitive and efficient detection method should now be tested in a larger clinical study.

Symptom Profile of Psychiatric Patients With Psychosis or Psychotic Mood Disorder in Prison.

There is evidence that psychiatric patients with psychotic or manic disorders who are incarcerated suffer from the same symptoms as psychiatric patients who are treated in the community. There are also indications that their symptoms might be more severe. The aim of this study was to examine the severity of psychotic and manic symptoms, as well as to collect information about the emotional functioning of patients admitted to a prison psychiatric ward. Incarcerated patients with a diagnosis of psychotic or a manic disorder were examined with the Brief Psychiatric Rating Scale-Expanded (BPRS-E). With the scores of 140 assessments, a symptom profile was created using the domains of the BPRS-E. This profile was compared with the clinical profile of three nonincarcerated patient groups described in literature with a diagnosis in the same spectrum. We found high scores on positive and manic psychotic symptoms and hostility, and low scores on guilt, depression, and negative symptoms. High scores on manic and psychotic symptoms are often accompanied by violent behavior. Low scores on guilt, depression, and negative symptoms could be indicative of externalizing coping skills. These characteristics could complicate treatment in the community and warrant further research along with clinical consideration.

Differences in executive functioning between violent and non-violent offenders.

BACKGROUND: A growing body of neuropsychological and neurobiological research shows a relationship between functioning of the prefrontal cortex and criminal and violent behaviour. The prefrontal cortex is crucial for executive functions such as inhibition, attention, working memory, set-shifting and planning. A deficit in these functions - a prefrontal deficit - may result in antisocial, impulsive or even aggressive behaviour. While several meta-analyses show large effect sizes for the relationship between a prefrontal deficit, executive dysfunction and criminality, there are few studies investigating differences in executive functions between violent and non-violent offenders. Considering the relevance of identifying risk factors for violent offending, the current study explores whether a distinction between violent and non-violent offenders can be made using an extensive neuropsychological test battery. METHOD: Male remand prisoners (N = 130) in Penitentiary Institution Amsterdam Over-Amstel were administered an extensive neuropsychological test battery (Cambridge Automated Neuropsychological Test Battery; CANTAB) measuring response inhibition, planning, attention, set-shifting, working memory and impulsivity/reward sensitivity. RESULTS: Violent offenders performed significantly worse on the stop-signal task (partial correlation r = 0.205, p = 0.024), a task measuring response inhibition. No further differences were found between violent and non-violent offenders. Explorative analyses revealed a significant relationship between recidivism and planning (partial correlation r = -0.209, p = 0.016). CONCLUSION: Violent offenders show worse response inhibition compared to non-violent offenders, suggesting a more pronounced prefrontal deficit in violent offenders than in non-violent offenders.

[The nature, extent and judicial response to aggression and violence directed against care workers in psychiatry]. / Agressie en geweld tegen hulpverleners in de psychiatrie; aard, omvang en strafrechtelijke reactie.

BACKGROUND: The Dutch government and the Council for public prosecutions consider aggression against and violence directed against public officers and care workers as unacceptable. But what is the attitude of these official bodies to violence directed against mental health care workers? AIM: To examine the nature and the prevalence of violence against mental health care professionals and the possible judicial consequences of this violence. METHOD: Dutch mental health professionals who work in the psychiatric hospitals and clinics were asked to fill in an online questionnaire about their experiences, over the past five years, of violence perpetrated by patients. RESULTS: The 1534 respondents had encountered violence regularly in the course of their work. Some of the violence was of a very serious nature and sometimes had severe consequences. Only a small number of the violent incidents were reported to the police and ultimately brought to court. The victims were poorly informed about the possible judicial consequences of the violence they had encountered. CONCLUSION: Not only should the mental health institutes counsel and inform the employees who have been victims of violence, they should also promote the development and implementation of an effective prosecution policy.

Violence against care workers in psychiatry: is prosecution justified?

The number of (severe) violent incidents against staff caused by psychiatric inpatients is high. Victims often do not report these incidents to the police, because of various reasons. But if they do report these incidents, the judicial authorities are often reluctant in prosecuting and convicting these patients. The central question in this article is 'in which cases is it appropriate to prosecute assaultive psychiatric patients?' In order to identify the influential factors in the decision in respectively reporting, prosecuting and convicting psychiatric patients who assault staff, a literature review has been performed. On the basis of this literature it is advised to report and investigate a case when the incident resulted in severe injury, the incident is a sexual offence, or when a patient repetitively causes violent incidents. Moreover, it appears that, although large amount of studies has been published on violence in psychiatry, the prosecution of violent psychiatric patients has hardly received any attention in the international literature. Empirical studies on this subject are suggested, in order to develop a uniform policy, which is embraced by all parties involved.

Body mass index of tannery workers in Kanpur, India.

During two cross sectional surveys in 1988 and 1994 the body mass index among tannery workers in Kanpur, India and its association with exposure to chemicals, dust and awkward ergonomic conditions, socio-economic and health status were studied. Fifty six per cent of the workers had in 1988 a BMI of less than 18.50, the cut-off value for malnutrition. In 1994 the proportion of malnourished workers had decreased to 41 per cent, being statistically significant lower than in 1988. Workers with a high exposure to lifting weights of more than 20 kg had significantly lower BMI than workers without this exposure. No other differences in mean BMI were found between workers without exposure to chemicals, dust and other awkward ergonomic conditions and workers with high or very high exposures, nor did the mean BMI of workers with occupational related conditions such as dermatitis, work related respiratory symptoms and low back pain differ from those without these conditions. There was no association between mean BMI and industrial modifications. In the 1994 survey workers who took sick leave in the year prior to the survey, workers of small/medium sized tanneries and workers without an ESI card had significantly lower BMI than workers without sick leave, workers of large tanneries and workers with an ESI card. Mean BMI of labourers with a monthly income of less than Rs 550 was significantly lower than that of tannery staff not engaged in leather work in this income group. No association was found between mean BMI and smoking, use of alcohol, educational level and income. The nutritional status of labourers in developing countries deserves more attention within the field of occupational health and safety.