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University of Southern California Dissertations and Theses
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Psychophysiological and behavioral characteristics of individuals with both antisocial personality disorder and schizophrenia-spectrum personality disorder
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Psychophysiological and behavioral characteristics of individuals with both antisocial personality disorder and schizophrenia-spectrum personality disorder
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Content
PSYCHOPHYSIOLOGICAL AND BEHAVIORIAL CHARACTERISTICS OF
INDIVIDUALS WITH BOTH ANTISOCIAL PERSONALITY DISORDER AND
SCHIZOPHRENIA-SPECTRUM PERSONALITY DISORDER
by
Robert August Schug
_____________________________________________________________________
A Thesis Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF ARTS
(PSYCHOLOGY)
December 2006
Copyright 2006 Robert August Schug
Table of Contents
List of Tables iii
List of Figures iv
Abstract v
Introduction 1
Method 5
Participants 5
Diagnostic Measures 5
Criminal Offending 6
Psychophysiological Measures 7
Results 9
Comorbidity 9
Criminal Offending 9
Psychophysiology 11
Discussion 13
References 20
ii
List of Tables
Table 1: Demographic Characteristics 25
Table 2: Criminal Offending 26
iii
List of Figures
Figure 1: Comorbidity Between SSPDs and ASPD 27
Figure 2: Skin Conductance Amplitude: Diagnostic Group Means by 28
Orienting Paradigm Stimuli
Figure 3: Boxplot of Skin Conductance Amplitude Data, Indicating 29
Skewness and Outliers
iv
Abstract
Although there is increasing evidence for comorbidity between schizophrenia-
spectrum personality disorders (SSPDs: paranoid, schizoid, and schizotypal) and
antisocial personality disorder (ASPD), we know surprisingly little about how this
comorbid group differs from either group alone. This study tests the hypothesis that
the comorbid group will be particularly characterized by reduced orienting and
arousal, and increased criminal offending. Self-report crime and skin conductance
data were collected on four diagnostic groups: SSPD only, ASPD only, SSPD with
ASPD, and healthy controls. Results indicated that the comorbid group reported
significantly more crime than the ASPDs, SSPDs, and controls. Additionally, the
comorbid group demonstrated reduced skin conductance orienting and arousal when
compared to controls. It is hypothesized that reduced orienting may represent an
attentional marker of prefrontal impairment predisposing to both antisocial and
schizotypal personality. Taking into account the comorbid relationship between
antisocial and schizotypal personality in future studies could help clarify the
heterogeneity in findings for both these disorders.
v
There is growing empirical evidence to support the existence of a relationship
between schizophrenia and crime. Multiple studies have consistently demonstrated
that higher rates of psychosis and schizophrenia are found in criminal or delinquent
populations, and that schizophrenia patients are more criminal and violent than the
general population (Raine, 2006; Walsh, Buchanan, & Fahy, 2002). International
studies have demonstrated that schizophrenics are at elevated risk for committing
homicide (see Schwartz, Petersen, & Skaggs, 2001), and that the prevalence rates of
homicides committed by persons with schizophrenia are comparatively high (8-20%
for men and 6-44% for women - Taylor & Gunn, 1999). Additionally, positive
psychotic symptoms correlate positively with violence (Bjorkly, 2002a, 2002b,
Krakowski, 2005), homicidal ideation (Schwartz et al., 2001), and homicidal
aggression (Planansky & Johnston, 1977). Despite this, research on this topic tends to
be fixated on reifying the link between crime and schizophrenia rather than pursuing
a second generation of research into possible common etiological factors of
schizophrenia and crime.
The schizophrenia-spectrum personality disorders (SSPDs - schizotypal,
paranoid, and schizoid personality disorders) may be a worthwhile focus for this next
wave of schizophrenia-crime research. Though SSPDs appear conceptually and
genetically related to schizophrenia (Chang et al., 2002; Raine, in press; Tykra,
Haslam, & Cannon, 1995), their relationship with crime has received little direct
attention compared to the larger body of research on schizophrenia. Identification of
SSPD comorbidity with antisocial personality disorder (ASPD) would be a logical
step toward establishing this relationship. While there appear to be few investigations
1
of the comorbidity between SSPDs and ASPD, studies incorporating constructs
related to SSPDs (e.g., prodromal symptoms, schizotypal personality scores) and
ASPD (e.g., aggression, antisociality, criminality, externalizing behavioral problems)
have produced mounting evidence for such comorbidity (Gosden, Kramp,
Gabrielsem, Andersen, & Sestoft, 2005; Raine, 1987; Raine, in press; Raine, Bihrle,
Venables, Mednick, & Pollock, 1999; Raine et al., 2006).
An important question that has received little attention to date concerns
whether there are particular behavioral and psychophysiological characteristics of
those comorbid for SSPD/ASPD. Investigations of comorbid schizophrenia and
ASPD suggest that this may be true, as this comorbidity appears to produce additively
deleterious behavioral effects (i.e., persistent criminality and amplified suffering;
Moran & Hodgins, 2004). Investigations of comorbid SSPD-related and ASPD-
related constructs also support the idea that comorbidity may be associated with more
prominent presentations of behaviors and traits related to criminality. For example,
higher rates of alcoholism have been found in schizotypal criminals (54.8%)
compared to criminals (23.8%), schizotypal noncriminals (13.9%) and controls
(21.7%; Raine et al., 1999). To date, few investigations of rates of comorbidity
between SSPDs and ASPD or their related constructs have been undertaken in
noninstitutionalized/nonincarcerated (i.e., community) populations, and differential
rates of criminality between SSPDs, ASPDs, and comorbid SSPD/ASPDs have not
been assessed. It remains to be seen whether the addition of a SSPD to ASPD
increases the degree of antisocial, criminal behavior over and above ASPD alone.
2
It is also conceivable that the comorbid SSPD/ASPD group differ to those
with only SSPD or only ASPD on psychophysiological markers common to these
conditions. One candidate marker to be considered is an abnormality in skin
conductance orienting—potentially reflecting dysfunctional attentional processes (see
Critchley, 2002, Damasio, 1994, and Raine & Venables, 1984). Schizophrenics,
schizotypals, and antisocials have demonstrated deficits in skin conductance
responding, although schizophrenics have also been characterized by both hyper- and
hyporesponding (Perry, Felger, & Braff, 1998; Raine, 2006). A number of
nondiagnostic studies have addressed this issue, and initial evidence appears to
support the hypothesis that schizophrenia-spectrum antisocials may be a biologically
distinct subgroup. For example, reduced SC amplitudes to orienting stimuli have been
found in secondary schizoid psychopaths relative to primary psychopaths (Blackburn,
1979), and in schizoid antisocial 15-year-old males relative to their nonschizoid
antisocial counterparts (Raine & Venables, 1984). Additionally, reduced SC orienting
response frequencies have been observed in schizotypal criminals (Raine, 1987). In
this context, Fowles (1993) has speculated that there may be a detached schizoid
subgroup of antisocial individuals who are hypothesized to be characterized by
electrodermal hyporeactivity. To date, no diagnostic studies appear to have
investigated electrodermal orienting deficits in those comorbid for ASPD and SSPD
to further test this notion.
Low autonomic arousal may constitute yet another distinct biological
characteristic of the comorbid group. Skin conductance level, a classic indicator of
autonomic arousal (Dawson, Schell, & Filion, 2000), is thought to characterize
3
antisocial behavior (Fowles, 1993). The relationship between skin conductance
arousal and ASPD has not received much attention, although low resting and task
electrodermal arousal were associated with psychopathy and conduct problems in a
recent meta-analysis (Lorber, 2004), and low electrodermal arousal has recently been
associated with serious delinquency and sensation seeking (Gatzke-Kopp, Raine,
Loeber, Stouthammer-Loeber, & Steinhauer, 2002). Evidence for a relationship
between electrodermal arousal and SSPDs is more mixed. Some authors have found
either lower or comparable levels of electrodermal arousal in schizophrenics
compared to controls (Maina, Barzega, Bellino, Bogetto, & Ravizza, 1995; Öhman,
1981), while others have found increased levels of electrodermal arousal in specific
types of schizophrenic and schizotypal individuals (Brekke, Raine, Ansel, Lencz, &
Bird, 1997; Dawson, Neuchterlein, Schell, Gitlin, & Ventura, 1994; Maina et al.,
1995; Raine, Venables, Mednick, & Mellingen, 2002). It is possible that the mixed
nature of these results may be attributed to differences across samples in degree of
comorbid antisocial behavior, and that clarification may be achieved by examining a
specific subgroup of schizophrenia-spectrum antisocials. Additionally, similar to the
previous work on orienting, studies have not employed clinical diagnoses in
investigations of electrodermal arousal deficits in comorbid SSPD/ASPD individuals.
The present study seeks to investigate the following three questions: First, is
there comorbidity between SSPDs and ASPD in a community sample? Second, if
such comorbidity exists, is this comorbid group more antisocial compared with
normal controls or to individuals with each disorder separately? Specifically, would
more criminal behavior be reported among the comorbid group than in each group
4
separately? Third, do SSPD/ASPD individuals demonstrate reduced SC orienting
and/or arousal when compared to ASPD individuals, SSPD individuals, and normal
controls?
Method
Participants
Adult males and females (total N = 101) were recruited from five temporary
agencies in the greater Los Angeles area. Because participation in the larger study
included magnetic resonance brain imaging (see Raine, Lencz, Bihrle, Lacasse, &
Collenti, 2000), participants were excluded if they were under 21 or over 45 years of
age; were nonfluent in English; were claustrophobic; or had a pacemaker, metal
implants, or a history of epilepsy. Qualified participants were informed of the nature
of the study and of the study’s potential risks and benefits. After giving signed,
informed consent, participants were individually tested over three days at a University
of Southern California (USC) research laboratory. All participants were paid. The
study and all its procedures were approved by the Institutional Review Board at USC.
Diagnostic Measures
Participants were administered the Structured Clinical Interviews for DSM-IV
Axis I Disorders (SCID I; First, Spitzer, Gibbon, & Williams, 1997) and Axis II
Personality Disorders (SCID II; First, Gibbon, Spitzer, Williams, & Benjamin, 1995).
The SCID I and II were administered by a clinical Ph.D. graduate student who had
received systematized training in diagnostic assessment (Ventura, Liberman, Green,
Shaner, & Minz, 1998).
5
From the entire sample, participants were classified into four groups, based
upon SCID II diagnoses and availability of self-report crime and skin conductance
data (see below). The schizophrenia spectrum personality disorders (SSPD) group
contained participants diagnosed with paranoid, schizoid, and/or schizotypal paranoid
personality disorders, with no comorbid antisocial personality disorder (n = 9). The
antisocial personality disorder group contained participants with ASPD diagnosis,
with no comorbid SSPDs (n = 14). The comorbid SSPD/ASPD group contained
participants who met diagnostic criteria for both SSPD and ASPD (n = 8). The
control group contained participants with no Axis II diagnoses (n = 48). Groups did
not significantly differ on gender, ethnicity, IQ, or socioeconomic status (see Table
1).
Criminal Offending
Two forms of criminal offending data were collected. First, criminal records
were searched and assessed for total numbers of arrests and convictions for each
participant (Raine et al., 2000). Second, each participant was administered an adult
extension (Raine et al., 2000) of the National Youth Survey self-report delinquency
measure (Elliot, Ageton, Huizinga, Knowles, & Canter, 1983). Self-report criminal
offending was operationalized as the total number of property, violence, and drug
offenses assessed by this 50-item instrument.
To encourage open reporting, a certificate of confidentiality was obtained
from the Secretary of Health, pursuant to Section 303(a) of Public Health Act 42.
Participants were informed that any information they might provide about
uninvestigated crimes could not be subpoenaed by any United States federal, state, or
6
local court. Participants were reminded of confidentiality during administration of the
measure and the limits to the confidentiality certificate.
Psychophysiological Measures
Skin conductance was measured during both rest and orienting conditions.
Apparatus and recording procedures. Participants were tested in a
temperature-controlled, light-and sound-attenuated psychophysiological recording
laboratory. Skin conductance was recorded from the distal phalanges of the first and
second fingers of the both hands (to maximize SC responsivity; Scerbo, Freedman,
Raine, Dawson, & Venables, 1992) using Beckman Ag/AgCl electrodes (1 cm.
diameter) with physiological saline (0.9% NaCl) in Unibase as electrolyte, with skin
contact area delineated using double-sided adhesive masks with a hole of 1 cm
diameter. Recordings were made using a Grass Model 7 polygraph (Quincy, MA) with
a constant 0.5V potential across electrodes to allow direct recording of skin conductance
(Venables and Christie, 1980). Participants were made as comfortable as possible and
asked to keep their hands and fingers as still as possible. They were then instructed that
after a 3 minute rest period they would hear a series of tones that would last about 5
minutes. The amount of time that elapsed from the end of electrode hook-up to the start
of the rest period was approximately two minutes.
Stimuli. A set of ten orienting stimuli were presented with inter-stimulus
intervals randomized between 25 and 40 seconds. Orienting stimuli consisted of a series
of six 75 dB tones of 1000 Hz frequency, 25 ms rise time, and one second duration.
These were followed by four “meaningful” stimuli consisting (in order of presentation)
of a reorienting stimulus (500 Hz tone of 75 dB intensity, one second duration), a
7
consonant-vowel stimulus (“da”, 0.35 seconds duration, 75 dB intensity), one 90 dB
stimulus (1 second duration, 1,000 Hz frequency), and one 90 dB white noise burst (1
second duration, 5 msec rise time).
Scoring. SCRs to each orienting stimulus were defined as increases in
conductivity > .05 microsiemens occurring within a latency window of 1-3 secs. post-
stimulus. The number of non-specific SC responses occurring during the three minute
rest period (using the same amplitude criterion as for SCRs above) was also scored;
while SC levels were recorded in microsiemens at the beginning and end of the rest
period, and at end of the orienting paradigm. Charts were scored blind to group
membership. Amplitudes were transformed using a square root transformation to reduce
skew and kurtosis as recommended by Venables and Christie (1980). Because levels for
the right and left hands were strongly correlated with each other at the respective time
points (i.e., correlations ranged from .77 to .83, ps < .001), the values for the two
hands at each time point were averaged. If data were missing for one hand (which
occurred on five occasions due to equipment failure), then data for the available hand
were used.
Statistical Analyses
In some cases, where within the data distributions there were serious
violations of the assumptions underlying traditional statistical techniques, additional
modern methods were used. It is known that for multiple reasons, conventional
methods for comparing means can have very poor power (e.g., Wilcox, 2005).
Comparing medians can reduce certain problems associated with methods for
comparing means, but a concern about using medians is that they trim too much of
8
the data, which again can result in relatively poor power. By trimming 20%, poor
power due to outliers, skewness, and variance can be reduced substantially, yet good
power is still achieved under standard assumptions. The employment of bootstrapping
techniques (see Wilcox, 2003) also seemed appropriate due to the small sizes of some
of the groups in the present study. Rather than assume normality to determine
appropriate critical values, bootstrap methods estimate appropriate critical values
using the available data.
Results
Comorbidity
Chi square analysis was employed to assess comorbidity between ASPD and
schizophrenia spectrum within the entire sample. Results indicated significant
differences in group diagnostic assignment ( χ
2
= 7.665, p = .006). Among those
diagnosed with SSPDs (n = 17), almost half (47.1%) had a comorbid diagnosis of
ASPD. Among those without SSPDs (n = 84), 16.7% were diagnosed with ASPD
(see Figure 1). Of the total sample, 69.3% were diagnosed with no Axis II condition,
13.9% with ASPD only, 8.9% with SSPDs only, and 7.9% with comorbid
SSPD/ASPD.
Criminal Offending
One-way Analysis of Variance (ANOVA) was employed to assess differences
in self-reported criminal offending among the four groups. Results indicated the
groups differed significantly, F(3) = 15.687, p < .001. Post hoc tests (Bonferroni)
indicated, as expected, that the ASPD group (n = 13, M = 21.62, SD = 12.45) reported
significantly more criminal offending than controls (n = 46, M = 11.34, SD = 5.61, p
9
= .004). However, the SSPD/ASPD group (n = 8, M = 33.75, SD = 17.37) reported
significantly more criminal offending than the ASPD group (p = .026), the SSPD
group (n = 8, M = 14.25, SD = 9.00, p < .001), and the control group (p < .001). A
boxplot of the self-report crime data indicated only minimal outliers and skewness,
thus additional modern bootstrapping methods involving trimmed means were not
employed to augment this analysis.
Additional ANOVAs were employed to assess differences in both the total
number of charges and convictions among the four groups. Results indicated that the
criminal records of the SSPD/ASPD group contained more charges and convictions
than those of the other groups (see Table 2); however, the groups did not differ
significantly on either the total number of charges, F(3) = 1.183, p = .322, or
convictions, F(3) = 1.181, p = .323. Boxplots of these data indicated significant
outliers in some cases, thus the aforementioned modern methods were employed to
augment conventional analyses. A percentile bootstrap method for 20% trimmed
means (see Wilcox, 2005) indicated that the criminal records of both the ASPD group
and the SSPD/ASPD group contained significantly more charges than the SSPD
group and the controls (ps = .0005 and < .0001, respectively, for ASPDs; and ps =
.006 and .003, respectively, for SSPD/ASPDs), though the ASPD and SSPD/ASPD
groups did not differ significantly from each other. An additional percentile bootstrap
method for 20% trimmed means indicated that the criminal records of both the ASPD
group and the SSPD/ASPD group contained significantly more convictions than the
SSPD group and the controls (ps = .0005 and .0010, respectively, for ASPDs; and ps
10
= .006 and .007, respectively, for SSPD/ASPDs), though the ASPD and SSPD/ASPD
groups again did not differ significantly from each other.
Psychophysiology
SC arousal. A repeated measures multivariate analysis of variance
(MANOVA) was employed to assess group differences in skin conductance level
across the initial three minute rest period and orienting paradigm. Results indicated
that the groups differed significantly over the three skin conductance level readings,
F(3) = 3.224, p = .027. Post hoc tests, however, indicated that comparisons were
largely nonsignificant after Bonferroni correction, and that only the SSPD/ASPD
group demonstrated a trend toward significantly lower SC arousal when compared to
controls (p = .069). The aforementioned repeated measures bootstrap method was
subsequently employed, and results confirmed that the SSPD/ASPD group
demonstrated significantly lower skin conductance level than controls (p < .001), and
that all other group differences remained nonsignificant.
SC responsivity: Frequency. An ANOVA was employed to assess the
difference in total number of SCORs during the entire orienting paradigm. Additional
ANOVAs were employed to assess differences in the total number of SCORs during
the first six orienting stimuli only, and then during the four meaningful stimuli only.
Boxplots of these data indicated relatively few outliers but significant skewness in
some cases. Consequently, modern methods were employed to augment conventional
analyses.
Results indicated that the groups differed significantly in number of SCORs
during the entire orienting paradigm, F(3) = 4.104, p = .009. Post hoc tests
11
(Bonferroni-corrected) indicated that only the SSPD/ASPD group (n = 8, M = .500,
SD = .598) demonstrated significantly fewer SCORs over the entire paradigm than
controls (n = 48, M = 2.583, SD = 2.025, p = .024). A bootstrap test of linear contrasts
using 20% trimmed means, however, indicated that both ASPD and SSPD/ASPD
groups demonstrated significantly fewer SCORs over the entire paradigm than
controls (ps = .027 and .002, respectively). Conventional ANOVA results also
indicated that the groups did not differ significantly in number of SCORs during the
first six orienting stimuli, though the same bootstrap linear contrast method revealed
that the ASPD group demonstrated significantly fewer SCORs than controls (p =
.045) during these stimuli. Additionally, conventional results indicated that the
groups differed significantly in number of SCORs during the four meaningful stimuli,
F(3) = 3.442, p = .021. Post hoc tests (Bonferroni) indicated that only the
SSPD/ASPD group (n = 8, M = .375, SD = .582) demonstrated significantly fewer
SCORs over the four meaningful stimuli than controls (n = 48, M = 1.990, SD =
1.435, p = .018). The bootstrap linear contrast method yielded identical results (p <
.0001).
SC responsivity: Amplitude. A repeated measures MANOVA was employed
to assess group differences in skin conductance amplitude across the entire orienting
paradigm (group means are displayed in Figure 2). Results indicated a trend toward
significance (F(3) = 2.033, p = .117). Additional repeated measures MANOVAs
indicated similar trends toward significance for the first six orienting stimuli (F(3) =
1.875, p = .141) and the four meaningful stimuli (F(3) = 1.915, p = .135).
12
A boxplot of the SC amplitude data indicated significant skewness and
numerous outliers (see Figure 3), which again made appropriate the application of
modern statistical methods. A repeated measures bootstrap method using 20%
trimmed means (see Wilcox, 2005) was employed to assess differences in SC
amplitude over the entire orienting paradigm. Results indicated that the SSPD/ASPD
group demonstrated significantly lower SC amplitude than controls (p = .0004).
This same repeated measures bootstrap method was subsequently employed to
assess differences in SC amplitude over the first six orienting stimuli, and over the
four meaningful stimuli. Results indicated that the SSPD/ASPD group demonstrated
significantly lower SC amplitude over the first six orienting stimuli than controls (p =
.0004). Additionally, results indicated that the SSPD group demonstrated significantly
lower SC amplitude over the four meaningful stimuli than controls (p < .0001), and
that the SSPD/ASPD group demonstrated significantly lower SC amplitude over these
stimuli than the ASPD group (p = .0004), the SSPD group (p < .0001), and controls
(p < .0001).
Discussion
This study set out to determine the prevalence of SSPD/ASPD comorbidity in
a community sample, and to determine if the comorbid group differ in socially
meaningful (criminality) and biological (autonomic) ways from individuals with each
condition separately. Results indicated significant comorbidity within this sample,
and that the comorbid group was characterized by more criminal offending and
reduced skin conductance orienting and arousal. Results have potential implications
for identifying a distinct subgroup of schizophrenia-spectrum antisocial individuals,
13
for better understanding the reason for the comorbidity between antisocial behavior
and schizophrenia, and possibly also the differential treatment, care, and management
of these individuals in therapeutic and forensic settings.
Findings suggest that ignoring the comorbid link between SSPDs and ASPD
may obfuscate findings in investigations of either condition separately. Studies of
antisocial populations have produced inconsistent results on electrodermal
responding, findings which may be clarified when schizophrenia-spectrum is
considered as a moderator. For example, it has been observed that while autonomic
underresponsivity does not characterize antisociality in general, a specific subgroup
of schizoid antisocials are characterized by autonomic nonresponding (Raine &
Venables, 1984). Subsequent research has indicated the same pattern of reduced SC
orienting in schizotypal-antisocial schoolboys and schizoid psychopaths (Raine et al.,
1999). Conversely, disparate findings of both reduced and increased orienting in
schizotypals may reflect the need to consider antisociality as a moderating variable,
where autonomic underesponding may characterize those schizotypals with antisocial
tendencies (Raine et al., 1999). One implication of the current study is that future
studies could significantly benefit by assessing both antisocial behavior and
schizotypal personality within the same population in order to elucidate risk factors
specific to each of these conditions.
The finding of reduced orienting particularly in the group comorbid for SSPD
and ASPD can be viewed within a neuroanatomical context predicated on the frontal
cortex. Specifically, SCOR is thought to be a marker for structural and functional
integrity of the prefrontal cortex, and impaired prefrontal structure / function have
14
been associated with both antisocial behavior and schizotypal personality. Structural
MRI and neurological studies on humans have demonstrated that reductions in the
integrity of the prefrontal cortex (lesions or reduction in area / volume) are associated
with reduced SCOR (Critchley, 2002). Functional MRI studies have shown that
SCORs during the Iowa gambling task result in activation of the ventromedial and
orbito-frontal cortex (Critchley, Elliott, Mathias, & Dolan, 2000). Visual orienting is
associated with increased activation in the anterior cingulate while re-orienting is
associated with increased activation in the middle frontal gyrus (Thiel et al., 2004).
Furthermore, stimuli that elicit an SCOR, compared to stimuli that do not, result in
activation in the hippocampus, anterior cingulate, and ventromedial prefrontal cortex
(Williams et al., 2000). Although the circuitry underlying the SCOR is complex and
involves multiple regions including the right inferior parietal cortex and amygdala,
the convergeance of findings from structural with functional imaging studies give rise
to the frontal cortex as a key higher brain area primarily associated with the SCOR.
This linkage of frontal structure / function with the SCOR, and the finding in
this study that reduced SCOR is particularly associated with those comorbid for
SSPD and ASPD, would give rise to the hypothesis that impaired frontal structure and
function would be observed in both SSPD and also ASPD. There is increasing
evidence from both neurocognitive and neuroimaging literatures to support this
hypothesis. There is growing neuropsychological evidence that juvenile delinquency,
antisocial behavior, criminality, and criminal psychopathy are associated with poorer
performance on tasks related to both orbitofrontal and ventromedial functioning
(Brower & Price, 2001; Lapierre, Braun, & Hodgins, 1995; Morgan & Lilienfeld,
15
2000; Yechiam et al., in press). Similarly, poor frontal functioning has been identified
as one of the best-replicated neurocognitive correlates of schizotypal personality
(Raine, 2006). Both structural and functional imaging studies have also observed
prefrontal impairments in both antisocial populations (Raine, 1997, Raine et al. 2000)
and also schizotypal populations (Raine et al. 2002), although there is stronger
evidence for structural impairments in schizophrenics compared to schizotypals.
Consequently, reduced SCOR may particularly characterize the comorbid group
because it is a peripheral marker for prefrontal impairment which in turn represents a
common risk factor to both personality disorders. It is hypothesized that reduced
orienting may represent an attentional marker of prefrontal impairment predisposing
to both antisocial and schizotypal personality. Taking into account the comorbid
relationship between antisocial and schizotypal personality in future studies could
help clarify the heterogeneity in findings for both these disorders.
Findings from the present study underscore the importance of modern
statistical methods such as trimmed means and bootstrapping (Wilcox, 2003), and
demonstrate how these techniques may be used to augment conventional analyses
when the assumptions of these traditional statistics are violated. Additionally, the
present study illustrates how important group differences may be elucidated using
alternative methods when conventional methods fail, and how the nature of data
distributions should be considered when choosing an appropriate statistical strategy.
While it is well-recognized in the literature that Type I errors are problematic, less
well-recognized but of importance in the early stages of an enquiry (in this case,
16
understanding ASPD- SSPD comorbidity) is that Type 2 errors can lead to equally
misleading conclusions.
One discrepancy in findings is that while significant results were observed for
self-report criminal offending, findings for official crime measures (charges and
convictions) were non-significant when comparing the comorbid and ASPD-only
groups. This may reflect a true result, and may be explained by the fact that official
records of charges and convictions are not comprehensive, and do not reflect criminal
offenses that are undetected. Law enforcement clearance rates clearly indicate that the
substantial majority of criminal activity goes unsolved (Seigel, 2006). An alternative
interpretation is that there are genuine differences between the comorbid and ASPD-
only groups, but that the study lacked power to detect these differences. That this
explanation should not be ruled out is suggested by the fact that the comorbid group
showed a 96.9% increase in charges and a 98.2% increase in convictions compared to
the ASPD-only group, differences that exceed the (statistically significant) 56.1%
increase in self-report crime. If correct, this in turn provides an example of how, in at
least some circumstances, modern statistical techniques such as trimmed means
(Wilcox, 2005) cannot entirely compensate for the lack of power in traditional
statistics, although the possibility of genuine null results cannot be discounted.
Additional research in the area of SSPD/ASPD comorbidity is clearly
warranted. Being the first study of its kind, replication of the present study’s findings
is clearly required. More efforts are needed to further validate the existence of
SSPD/ASPD comorbidity, especially in community samples. Future studies should
17
incorporate the use of corroborating information (i.e., collateral interviews, official
crime records) to enhance the quality of self-report data.
Findings may have several implications at basic research, clinical
intervention, and forensic levels. First at a research level, while researchers have
made significant advances in the understanding of both SSPDs and ASPD separately,
conceptualizing those comorbid for SSPD/ASPD as a distinct group may clarify and
strengthen findings for future investigations not only of this group, but also of “pure”
SSPD or ASPD samples. The importance of this type of clarification and the
exploration of an etiologically divergent subgroup of schizophrenia-spectrum
antisocials has been underscored in the literature (Fowles, 1993). Second, at a clinical
treatment level, outcomes of psychopharmacological treatment programs may vary
markedly between comorbids and “pure” cases; techniques which demonstrate
effectiveness in SSPDs and ASPDs separately (see Bilder, 2006, Hirose, 2001, Lösel,
2001, and Walker, Thomas, & Allen, 2003) may be less effective in comorbid
SSPD/ASPD individuals. Ultimately, alternative treatment strategies may need to be
developed for this comorbid group. Third, at a forensic level, comorbidity may have
practical implications in the evaluation of dangerousness and potential for
reoffending. If a particular diagnostic entity (i.e., SSPD/ASPD comorbids) has been
shown to demonstrate increased rates of criminality, an offender with such a
symptom presentation may require alternate sentencing requirements to both ensure
public safety and facilitate more effective rehabilitation.
In conclusion, results of this initial study indicate that those comorbid for both
SSPD and ASPD differ in both behavioral and psychophysiological ways to those
18
with just one or other of these clinical conditions. The finding of reduced
electrodermal orienting in the comorbid group confirms and extends findings of three
prior studies observing this same effect, and may reflect an attentional resource
allocation deficit linked to the prefrontal cortex which is common to both clinical
groups. Further research on this comorbid condition is warranted, particularly because
it presents with significantly higher rates of increased criminal activity.
19
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Table 1. Demographic Characteristics
Diagnostic Group
SSPD ASPD SSPD/ASPD Controls
Gender
Male 8 14 7 39
Female 1 0 1 9
Ethnicity
Asian 0 0 0 2
Black 4 7 4 8
Hispanic 1 1 1 7
White 4 5 3 29
Other 0 1 0 2
Full Scale IQ M = 93.56
SD = 12.739
M = 99.21
SD = 11.233
M = 94.00
SD = 13.763
M = 100.42
SD = 15.941
SES M = 36.11
SD = 13.430
M = 35.29
SD = 7.580
M = 34.38
SD = 11.045
M = 35.32
SD = 11.797
25
Table 2. Criminal Offending
Diagnostic Group
SSPD
M (SD)
ASPD
M (SD)
SSPD/ASPD
M (SD)
Controls
M (SD)
Self-Report Crime 14.25 (9.00)
a
21.62 (12.45)
b
33.75 (17.38)
c
11.35 (5.61)
a
Charges 0.44 (0.88)
a
4.57 (4.00)
b
9.00 (8.82)
b
3.44 (11.54)
a
Convictions 0.11 (0.33)
a
1.64 (1.74)
b
3.25 (3.33)
b
1.25 (4.17)
a
Note. Means in the same row that do not share subscripts differ at p < .05 in the
Bonferroni correction (self-report crime) or the percentile bootstrap method for 20%
trimmed means (charges, convictions).
26
Figure 1. Comorbidity Between SSPDs and ASPD
0
10
20
30
40
50
60
70
80
ASPD Present ASPD Absent
Number of Individuals
SSPD Present
SSPD Absent
27
Figure 2. Skin Conductance Amplitude: Diagnostic Group Means by Orienting
Paradigm Stimuli
0
0.1
0.2
0.3
0.4
0.5
0.6
OS1 OS2 OS3 OS4 OS5 OS6 MS1 MS2 MS3 MS4
Orienting Paradigm Stimuli
SC Amplitude (mS)
ASPD
SSPD
SSPD/ASPD
Controls
Note: OS = Orienting Stimulus. MS = Meaningful Stimulus.
28
Figure 3. Boxplot of Skin Conductance Amplitude Data, Indicating Skewness and
Outliers
0.0 0.1 0.2 0.3
SC Amplitude (mS)
ASPD SSPD Controls SSPD/ASPD
4 Groups X 10 Stimuli
Note. Rectangular boxes represent distribution of data for each stimulus presentation
(arranged side-by-side, in ascending chronological order 1-10, from left to right), for
each diagnostic group. Medians are represented by white bands within the dark-
colored boxes. Upper and lower quartiles (i.e., where the middle half of the data lie)
are represented by the ends of the dark-colored boxes. Adjacent values (i.e., smallest
and largest values not declared outliers) are indicated by the whiskers ( ┌┐). Outliers
are represented by the single dashed lines (see Wilcox, 2003). Distributions centered
at 0.0 mS, with relatively minimal or no variability, appear as the symbol (H).
29
Abstract (if available)
Abstract
Although there is increasing evidence for comorbidity between schizophrenia-spectrum personality disorders (SSPDs: paranoid, schizoid, and schizotypal) and antisocial personality disorder (ASPD), we know surprisingly little about how this comorbid group differs from either group alone. This study tests the hypothesis that the comorbid group will be particularly characterized by reduced orienting and arousal, and increased criminal offending. Self-report crime and skin conductance data were collected on four diagnostic groups: SSPD only, ASPD only, SSPD with ASPD, and healthy controls. Results indicated that the comorbid group reported significantly more crime than the ASPDs, SSPDs, and controls. Additionally, the comorbid group demonstrated reduced skin conductance orienting and arousal when compared to controls. It is hypothesized that reduced orienting may represent an attentional marker of prefrontal impairment predisposing to both antisocial and schizotypal personality. Taking into account the comorbid relationship between antisocial and schizotypal personality in future studies could help clarify the heterogeneity in findings for both these disorders.
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Schug, Robert August
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Core Title
Psychophysiological and behavioral characteristics of individuals with both antisocial personality disorder and schizophrenia-spectrum personality disorder
School
College of Letters, Arts and Sciences
Degree
Master of Arts
Degree Program
Psychology
Publication Date
10/19/2006
Defense Date
10/01/2006
Publisher
University of Southern California
(original),
University of Southern California. Libraries
(digital)
Tag
antisocial,Crime,OAI-PMH Harvest,psychophysioloogy,schizophrenia spectrum
Language
English
Advisor
Raine, Adrian (
committee chair
), Dawson, Michael E. (
committee member
), Wilcox, Rand R. (
committee member
)
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schug@usc.edu
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