Research reportVolumetric structural brain abnormalities in men with schizophrenia or antisocial personality disorder
Introduction
Violent behaviour is disproportionately over-represented in individuals with certain mental disorders compared with the general population [15]. Schizophrenia and antisocial personality disorder (APD) are the disorders most implicated in violence [15], [47]. Existing psycho-physiological and neuropsychological studies have demonstrated similar impairments in APD and the related dimensional concept of psychopathy, as well as in schizophrenia [4], [22], [36]. These overlapping deficits include impairment in the ability to correctly interpret and recognise facial affect [4], [5], [22] and decreased executive functioning capacity, when compared to healthy control subjects [12], [36].
Although the role of biological factors in relation to mental disorder remains uncertain, these functional impairments have been used as evidence of neural pathology, which may be directly or indirectly involved in the expression of violent behaviour. Animal studies and theoretical accounts suggest that aggression is elicited by neurological trauma or lesions to the prefrontal cortex (PFC), temporal lobes and hypothalamus [49], [41]. These areas are associated with higher intellectual functioning and goal-directed behaviour but are also implicated in mediating emotion and inhibitory mechanisms [8]. Although many studies refer to ‘aggression’; a catchall category likely to refer to attitude or angry affect as well as physical acts, the current study is concerned with actual physical violence, independently recognised as serious in all cases.
The advent of neuroimaging techniques such as magnetic resonance imaging (MRI) has helped investigators to uncover structural neural characteristics and abnormalities occurring in people who have a propensity for violence. Reviews of structural MRI investigations among people with schizophrenia [40], [52] have consistently concluded that schizophrenia appears to be associated with reduction in whole brain size, cortical grey matter, thalamus, temporal and frontal lobe volume, as well as increased cerebral ventricle and basal ganglia volume. Studies specifically examining individuals with schizophrenia and a history of violence have reported reductions in whole brain and hippocampal volume [7], temporal lobe volume reductions [50] and frontal lobe white matter abnormalities [24].
There are fewer neuroimaging studies of people with APD. One recent review of APD research [8] noted consistent findings of reductions in the temporal lobe (particularly the amygdala) and frontal lobes. A structural MRI study [13] that examined antisocial and borderline personality disordered sample reported reductions in temporal lobe volume when compared to healthy controls, but did not find any significant frontal lobe volume decrease. Other investigations of personality-disordered samples (including APD) have reported ventricular enlargement [51] and reductions in prefrontal cortex grey matter [37] when compared to healthy individuals. Additionally, a study of psychopathy in APD conducted by Laakso et al. [29] demonstrated a strong negative correlation between antisocial traits and posterior hippocampus volume, where higher trait scores were linked to lower volume. Such reductions in temporal lobe size (in addition to the hippocampus and amygdala) are linked to impaired emotional processing in APD [28], increases in impulsivity and predisposition towards violent behaviour [9]. These regions have also been implicated in schizophrenia populations, where similar observations of fronto-temporal abnormalities have been associated with hallucinations and delusions, and the onset of psychosis [30], [45]. Impaired emotional processing is a problem also for many people with schizophrenia, although delusions are the features that have been most consistently related to violent acts [47].
Previous structural MRI investigations among people with mental disorder who have been violent have grouped together diverse psychiatric conditions under the common factor of ‘violence’, or have included subjects with co-morbid mental disorders [8]. With these limitations in mind, in the current study we sought, using structural MRI methods, to compare neural differences in groups of men diagnosed with APD or with schizophrenia, in the latter case with and without history of violence, as well as healthy controls. The study focussed on men due to the relative scarcity of women in forensic secure settings that would fulfil the study's inclusion criteria, as well as the fact that a purely male sample would eliminate confounding factors that may be related to sex.
Based on the existing literature, it was hypothesised that: (i) the APD group would have smaller temporal lobes, pre-frontal cortex and constituent limbic system components (amygdala and hippocampus) compared to controls, (ii) both violent and non-violent groups with schizophrenia would display a reduction in whole brain volume as well as in limbic structures and the thalamus but increased volumes of lateral ventricles, caudate nucleus and putamen compared to controls, and (iii) the violent men with schizophrenia would show more extensive abnormalities in structural volumes than their non-violent peers, due to the combination of violence and pre-existing mental illness.
Section snippets
Subjects
The violent men with mental disorder were recruited from one high security hospital (Broadmoor) and one medium security hospital unit (Denis Hill Unit, Bethlem Royal Hospital). The non-violent men with schizophrenia were recruited from open psychiatric settings in the South London and Maudsley Trust, London, and the healthy control men were recruited by advertisement and employment agencies local to the latter Trust. An attempt was made to recruit violent men without either personality disorder
Demographic and clinical data
Means and standard deviations and ANOVA comparisons for demographic and clinical variables are provided in Table 1. Chi-square analysis of ethnicity (χ2 = 13.932, p = 0.53), education (χ2 = 9.76, p = 0.37) or socio-economic status (χ2 = 28.35, p = 0.06) did not reveal any significant group differences. The VS and APD groups did not statistically differ in the subtypes of violent crimes they committed (χ2 = 0.397, p = 0.98). On other demographic and clinical measures, the four groups were similar but they did
Discussion
This study investigated structural abnormalities in brain regions specifically implicated as anomalous in men with schizophrenia and APD that are violence prone. The findings revealed differential as well as shared abnormalities in the two violent groups and the two schizophrenia groups, in addition to revealing certain features specific to individual groups.
Specifically, compared to controls, the APD group displayed reductions in whole brain volume, temporal lobe and increases in putamen
Acknowledgments
We express our appreciation to the staff of Broadmoor Special Hospital and the Denis Hill Unit of the Royal Bethlem Hospital for assistance with this study. We would also like to thank Prof. Sheilagh Hodgins for her comments on an earlier draft of this paper. This study was funded by grants from The Zito Trust and the Community Fund, UK, and the Stanley Medical Research Institute, USA. Veena Kumari holds a Wellcome Trust Senior Research Fellowship in Basic Biomedical Science.
References (51)
- et al.
The relationship between brain structure and neurocognition in schizophrenia: a selective review
Schizophr Res
(2004) - et al.
Improving stereological estimates for the volume of structures identified in three-dimensional arrays of spatial data
J Neurosci Meth
(1997) A cognitive developmental approach to mortality: investigating the psychopath
Cognition
(1995)- et al.
Ventricular enlargement in schizophrenia: a primary change in the temporal lobe?
Schizophr Res
(2003) - et al.
A prospective follow-up study of brain morphology and cognition in first-episode schizophrenic patients: preliminary findings
Biol Psychiat
(1995) - et al.
Quantitative frontal and temporal structural MRI studies in personality-disordered offenders and control subjects
Psychiat Res
(2002) - et al.
Dissociable executive functions in the dynamic control of behaviour: inhibition, error detection, and correction
Neuroimage
(2002) - et al.
Impairment in basal limbic function in schizophrenia during affect recognition
Psychiat Res
(2003) - et al.
Caudate, putamen, and globus pallidus volume in schizophrenia: a quantitative MRI study
Psychiat Res
(1995) - et al.
Frontal white matter microstructure, aggression, and impulsivity in men with schizophrenia: a preliminary study
Biol Psychiat
(2002)