Multi-modal risk factors differentiate suicide attempters from ideators in military veterans with major depressive disorder.

BACKGROUND: The suicide rate for United States military veterans is 1.5× higher than that of non-veterans. To meaningfully advance suicide prevention efforts, research is needed to delineate factors that differentiate veterans with suicide attempt/s, particularly in high-risk groups, e.g., major depressive disorder (MDD), from those with suicidal ideation (no history of attempt/s). The current study aimed to identify clinical, neurocognitive, and neuroimaging variables that differentiate suicide-severity groups in veterans with MDD. METHODS: Sixty-eight veterans with a DSM-5 diagnosis of MDD, including those with no ideation or suicide attempt (N = 21; MDD-SI/SA), ideation-only (N = 17; MDD + SI), and one-or-more suicide attempts (N = 30; MDD + SA; aborted, interrupted, actual attempts), participated in this study. Participants underwent a structured diagnostic interview, neurocognitive assessment, and 3 T-structural/diffusion tensor magnetic-resonance-imaging (MRI). Multinomial logistic regression models were conducted to identify variables that differentiated groups with respect to the severity of suicidal behavior. RESULTS: Relative to veterans with MDD-SI/SA, those with MDD + SA had significantly higher left cingulum fractional anisotropy, decreased attentional control on emotional-Stroop, and faster response time with intact accuracy on Go/No-Go. Relative to MDD + SI, MDD + SA had higher left cingulum fractional anisotropy and faster response time with intact accuracy on Go/No-Go. LIMITATIONS: Findings are based on retrospective, cross-sectional data and cannot identify causal relationships. Also, a healthy control group was not included given the study's focus on differentiating suicide profiles in MDD. CONCLUSIONS: This study suggests that MRI and neurocognition differentiate veterans with MDD along the suicide-risk spectrum and could inform suicide-risk stratification and prevention efforts in veterans and other vulnerable populations.

Smaller rostral cingulate volume and psychosocial correlates in veterans at risk for suicide.

Suicide research/clinical work remain in dire need of effective tools that can better predict suicidal behavior. A growing body of literature has started to focus on the role that neuroimaging may play in helping explain the path towards suicide. Specifically, structural alterations of rostral anterior cingulate cortex (rost-ACC) may represent a biological marker and/or indicator of suicide risk in Major Depressive Disorder (MDD). Furthermore, the construct of "grit," defined as perseverance for goal-attainment and shown to be associated with suicidality, is modulated by rost-ACC. The aim was to examine relationships among rost-ACC gray matter volume, grit, and suicidality in U.S. Military Veterans. Participants were age-and-sex-matched Veterans with MDD: with suicide attempt (MDD+SA:n = 23) and without (MDD-SA:n = 37). Groups did not differ in depression symptomatology. Participants underwent diagnostic interview, clinical symptom assessment, and 3T-MRI-scan. A Group (SA-vs.-No-SA) x Cingulate-region (rostral-caudal-posterior) x Hemisphere (left-right) mixed-model-multivariate-ANOVA was conducted. Left-rost-ACC was significantly smaller in MDD+SA, Group x Cingulate-region x Hemisphere-interaction. Lower grit and less left-rost-ACC gray matter each predicted suicide attempt history, but grit level was a more robust predictor of SA. Both structural alterations of rost-ACC and grit level represent potentially valuable tools for suicide risk assessment.

Cingulate and hippocampal subregion abnormalities in combat-exposed veterans with PTSD.

BACKGROUND: The hippocampus and cingulate gyrus are strongly interconnected brain regions that have been implicated in the neurobiology of post-traumatic stress disorder (PTSD). These brain structures are comprised of functionally distinct subregions that may contribute to the expression of PTSD symptoms or associated cardio-metabolic markers, but have not been well investigated in prior studies. METHODS: Two divisions of the cingulate cortex (i.e., rostral and caudal) and 11 hippocampal subregions were investigated in 22 male combat-exposed veterans with PTSD and 22 male trauma-exposed veteran controls (TC). Cardio-metabolic measures included cholesterol, body mass index, and mean arterial pressure. RESULTS: Individuals with PTSD had less caudal cingulate area compared to TC even after controlling for caudal cingulate thickness. Total hippocampus volume was lower in PTSD compared to TC, accounted for by differences in CA1-CA4, granule cell layer of the dentate gyrus, molecular layer, and subiculum. Individuals with PTSD had higher mean arterial pressure compared to TC, which correlated with hippocampus volume only in the PTSD group. LIMITATIONS: Sample size, cross-sectional analysis, no control for medications and findings limited to males. CONCLUSIONS: These data demonstrate preferential involvement of caudal cingulate area (vs. thickness) and hippocampus subregions in PTSD. The inverse association between hippocampus volume and mean arterial pressure may contribute to accelerated aging known to be associated with PTSD.

Frontotemporal thalamic connectivity in schizophrenia and schizotypal personality disorder.

Schizotypal personality disorder (SPD) resembles schizophrenia, but with attenuated brain abnormalities and the absence of psychosis. The thalamus is integral for processing and transmitting information across cortical regions and widely implicated in the neurobiology of schizophrenia. Comparing thalamic connectivity in SPD and schizophrenia could reveal an intermediate schizophrenia-spectrum phenotype to elucidate neurobiological risk and protective factors in psychosis. We used rsfMRI to investigate functional connectivity between the mediodorsal nucleus (MDN) and pulvinar, and their connectivity with frontal and temporal cortical regions, respectively in 43 healthy controls (HCs), and individuals in the schizophrenia-spectrum including 45 psychotropic drug-free individuals with SPD, and 20 individuals with schizophrenia-related disorders [(schizophrenia (n = 10), schizoaffective disorder (n = 8), schizophreniform disorder (n = 1) and psychosis NOS (n = 1)]. Individuals with SPD had greater functional connectivity between the MDN and pulvinar compared to individuals with schizophrenia. Thalamo-frontal (i.e., between the MDN and rostral middle frontal cortex) connectivity was comparable in SPD and HCs; in SPD greater connectivity was associated with less symptom severity. Individuals with schizophrenia had less thalamo-frontal connectivity and thalamo-temporal (i.e., pulvinar to the transverse temporal cortex) connectivity compared with HCs. Thalamo-frontal functional connectivity may be comparable in SPD and HCs, but abnormal in schizophrenia, and that this may be protective against psychosis in SPD.

Anomalous Amygdala Habituation to Unpleasant Stimuli Among Unmedicated Individuals With Borderline Personality Disorder and a History of Self-Harming Behavior.

Self-harming behavior (SB) is one of the diagnostic criteria for borderline personality disorder (BPD). However, it is not exhibited by all individuals with BPD. Furthermore, studies examining the neural correlates of SB in BPD are lacking. Given research showing that BPD patients have difficulty habituating to affective stimuli, this study investigated whether anomalous amygdala activation is specific to BPD patients with SB. The authors used fMRI to compare amygdala activation in BPD patients with SB (n = 15) to BPD patients without SB (n = 18) and healthy controls (n = 32) during a task involving pleasant, neutral, and unpleasant pictures, presented twice. BPD patients with SB demonstrated greater amygdala activity during the second presentation of unpleasant pictures. Results highlight neurobiological differences in BPD patients with and without SB and suggest that anomalous amygdala habituation to unpleasant stimuli may be related to SB.

Diffusion tensor anisotropy in the cingulate gyrus in schizophrenia.

It has been proposed that schizophrenia results partly from altered brain connectivity. The anterior cingulate cortex in particular has been demonstrated to be affected in schizophrenia, with studies reporting reduced volume, altered neuronal arrangement, decreased anisotropy in diffusion tensor images, and hypometabolism. We used a 3T Siemens scanner to acquire structural and diffusion tensor imaging in age-and sex-matched groups of 41 adults with chronic schizophrenia, 6 adults with recent-onset schizophrenia, and 38 healthy control subjects. We manually traced the anterior and posterior cingulate gyri on all subjects and then compared the volume and anisotropy across groups for the left and right anterior and posterior cingulate gyri. The anterior cingulate gyrus was divided axially into six equal segments, and the posterior cingulate gyrus into two segments. Volume was calculated for the anterior and posterior gyri, and average anisotropy was then calculated for each individual segment, looking separately at gray and white matter. We found decreased overall relative left and right gray matter volume in the anterior cingulate gyrus in persons with schizophrenia compared with healthy controls. Additionally, in both gray and white matter of the cingulate, we found that recent-onset patients had the highest anisotropy, chronic patients had the lowest, and controls were intermediate. These results provide additional evidence for the presence of both white and gray matter abnormalities in the cingulate gyrus, which has been implicated in schizophrenia.

Neuroimaging predictors of response to cognitive remediation and social skills training: A pilot study in veterans with schizophrenia.

Neuroimaging may predict response to cognitive remediation therapy and social skills training (CRT + SST) in schizophrenia. Identifying biological predictors of response is crucial for treatment decision making given not all patients respond to such interventions. Nineteen veterans with schizophrenia enrolled in an 8-week trial of CRT + SST. Ten participants completed diffusion tensor imaging (DTI) at baseline. Baseline fractional anisotropy (FA) in the superior longitudinal fasciculus (SLF) and overall average FA predicted improvements in visual-spatial working memory, and social cognition, respectively. Neuroimaging may be useful in identifying therapeutic targets in schizophrenia.

Short communication: Diffusion tensor anisotropy in the cingulate in borderline and schizotypal personality disorder.

Despite considerable phenomentological differences between borderline personality disorder (BPD) and schizotypal personality disorder (SPD), research increasingly provides evidence that some BPD symptoms overlap with SPD symptoms (e.g., disturbed cognitions). We examined the cingulate, a brain region implicated in the pathophysiology of both disorders, to determine similarities/differences between the groups, and similarities/differences from healthy controls (HC's). 3T structural and diffusion tensor magnetic resonance imaging scans were acquired in BPD (n = 27), SPD (n = 32), HC's (n = 34). Results revealed that BPD patients exhibited significantly lower FA in posterior cingulate white matter compared to HC's (p = 0.04), but SPD patients did not.

Frontal-striatal-thalamic mediodorsal nucleus dysfunction in schizophrenia-spectrum patients during sensorimotor gating.

Prepulse inhibition (PPI) refers to a reduction in the amplitude of the startle eyeblink reflex to a strong sensory stimulus, the pulse, when it is preceded shortly by a weak stimulus, the prepulse. PPI is a measure of sensorimotor gating which serves to prevent the interruption of early attentional processing and it is impaired in schizophrenia-spectrum patients. In healthy individuals, PPI is more robust when attending to than ignoring a prepulse. Animal and human work demonstrates that frontal-striatal-thalamic (FST) circuitry modulates PPI. This study used functional magnetic resonance imaging (fMRI) to investigate FST circuitry during an attention-to-prepulse paradigm in 26 unmedicated schizophrenia-spectrum patients (13 schizotypal personality disorder (SPD), 13 schizophrenia) and 13 healthy controls. During 3T-fMRI acquisition and separately measured psychophysiological assessment of PPI, participants heard an intermixed series of high- and low-pitched tones serving as prepulses to an acoustic-startle stimulus. Event-related BOLD response amplitude curves in FST regions traced on co-registered anatomical MRI were examined. Controls showed greater activation during attended than ignored PPI conditions in all FST regions-dorsolateral prefrontal cortex (Brodmann areas 46, 9), striatum (caudate, putamen), and the thalamic mediodorsal nucleus. In contrast, schizophrenia patients failed to show differential BOLD responses in FST circuitry during attended and ignored prepulses, whereas SPD patients showed greater-than-normal activation during ignored prepulses. Among the three diagnostic groups, lower left caudate BOLD activation during the attended PPI condition was associated with more deficient sensorimotor gating as measured by PPI. Schizophrenia-spectrum patients exhibit inefficient utilization of FST circuitry during attentional modulation of PPI. Schizophrenia patients have reduced recruitment of FST circuitry during task-relevant stimuli, whereas SPD patients allocate excessive resources during task-irrelevant stimuli. Dysfunctional FST activation, particularly in the caudate may underlie PPI abnormalities in schizophrenia-spectrum patients.

Internal capsule, corpus callosum and long associative fibers in good and poor outcome schizophrenia: a diffusion tensor imaging survey.

BACKGROUND: Prior voxelwise studies of white matter anisotropy found widespread reductions involving all major fiber tracts of the schizophrenic brain. We set out to confirm these exploratory findings and evaluate their relation to illness severity using a hypothesis-driven region-of-interest approach. METHODS: 104 schizophrenia patients (51 with good outcomes, 53 with poor outcomes) and 41 matched comparison subjects participated in the study. Regions of interest were selected on the basis of published voxelwise findings and placed within major fiber tracts using Talairach's stereotaxic coordinates. RESULTS: Fractional anisotropy reductions in schizophrenia patients were confirmed in the left cingulum, anterior thalamic radiation, fronto-occipital and inferior longitudinal fasciculi, as well as bilaterally in the corpus callosum, anterior and posterior limbs of internal capsule, superior longitudinal fasciculus, optic radiation, and frontotemporal extrafascicular white matter. Anisotropy reductions were more extensive in patients with poor outcomes ("Kraepelinian"), particularly in the posterior corpus callosum, fronto-occipital fasciculus, left optic radiation and frontotemporal white matter. Lower anisotropy in the right hemisphere tracts was associated with more prominent positive symptomatology, whereas negative symptoms were inversely associated with anisotropy values in both hemispheres. CONCLUSIONS: These results support a global neural disconnectivity in schizophrenia patients, which is more severe in those with poor clinical outcomes.

The effect of doxapram on brain imaging in patients with panic disorder.

Administration of doxapram hydrochloride, a respiratory stimulant, is experienced by panic disorder patients to be similar to panic attacks but has reduced emotional effect in normal volunteers, thus providing a laboratory model of panic for functional imaging. Six panic patients and seven normal control subjects underwent positron emission tomography with (18)F-deoxyglucose imaging after a single-blinded administration of either doxapram or a placebo saline solution. Saline and doxapram were administered on separate days in counterbalanced order. Patients showed a greater heart rate increase on doxapram relative to saline than controls, indicating differential response. On the saline placebo day, patients had greater prefrontal relative activity than controls. In response to doxapram, patients tended to decrease prefrontal activity more than controls, and increased cingulate gyrus and amygdala activity more than controls. This suggests that panic disorder patients activate frontal inhibitory centers less than controls, a tendency that may lower the threshold for panic.

Diffusion tensor imaging in schizophrenia.

BACKGROUND: Alignment of white matter axons as inferred from diffusion tensor imaging has indicated changes in schizophrenia in frontal and frontotemporal white matter. METHODS: Diffusion tensor anisotropy and anatomical magnetic resonance images were acquired in 64 patients with schizophrenia and 55 normal volunteers. Anatomical images were acquired with a magnetization prepared rapid gradient echo sequence, and diffusion tensor images used a pulsed gradient spin-echo acquisition. Images were aligned and warped to a standard brain, and anisotropy in normal volunteers and patients was compared using significance probability mapping. RESULTS: Patients showed widespread areas of reduced anisotropy, including the frontal white matter, the corpus callosum, and the frontal longitudinal fasciculus. CONCLUSIONS: These findings, which are consistent with earlier reports of frontal decreases in anisotropy, demonstrate that the effects are most prominent in frontal and callosal areas and are particularly widespread in frontal white matter regions.

White matter fractional anisotropy and outcome in schizophrenia.

OBJECTIVE: Disparate white matter fractional anisotropy (FA) findings have been reported in patients with schizophrenia in recent years. This may in part reflect heterogeneity of subjects in the studies, including differences in outcome and severity of the illness. We examined whether there is a relationship between white matter FA and outcome in patients with schizophrenia. METHOD: Diffusion-tensor images were obtained in 41 normal subjects and 104 patients with schizophrenia, divided into good-outcome (n=51) and poor-outcome (Kraepelinian; n=53) subtypes based on their ability for self-care. White matter FA and its relationship to regional tissue volumes were evaluated across 40 individual Brodmann's areas using a semi-automated parcellation technique. RESULTS: Overall white matter FA was lower in schizophrenia patients than normal subjects, with regional reductions in widespread temporoparietal and selected prefrontal white matter regions. In schizophrenia patients, lower regional white matter FA was associated with lower regional gray matter volumes. In comparison to normal subjects, overall white matter FA was reduced in patients with poor outcomes in both hemispheres, but to a lesser extent and only in the right hemisphere in good-outcome patients. Lower regional FA was associated with larger regional white matter volumes in good-outcome group. CONCLUSIONS: Global FA reductions implicate white matter as tissue type in the pathophysiology of schizophrenia. In contrast to poor outcome, good outcome in schizophrenia patients may be associated with less extensive FA reductions, higher FA in regional frontal and cingulate white matter, and correlated increases in regional white matter volumes, particularly in the left hemisphere.

Diffusion tensor imaging of frontal lobe white matter tracts in schizophrenia.

We acquired diffusion tensor and structural MRI images on 103 patients with schizophrenia and 41 age-matched normal controls. The vector data was used to trace tracts from a region of interest in the anterior limb of the internal capsule to the prefrontal cortex. Patients with schizophrenia had tract paths that were significantly shorter in length from the center of internal capsule to prefrontal white matter. These tracts, the anterior thalamic radiations, are important in frontal-striatal-thalamic pathways. These results are consistent with findings of smaller size of the anterior limb of the internal capsule in patients with schizophrenia, diffusion tensor anisotropy decreases in frontal white matter in schizophrenia and hypothesized disruption of the frontal-striatal-thalamic pathway system.

Correlations between MRI-assessed volumes of the thalamus and cortical Brodmann's areas in schizophrenia.

BACKGROUND: We compared the thalamic-cortical volumetric correlational patterns in patients with schizophrenia and normal comparison subjects, and evaluated their relations to outcome. METHODS: High-resolution MR images were acquired in patients with schizophrenia (n=106) and normal comparison subjects (n=42). Patients were divided into good-outcome (n=52) and poor-outcome (Kraepelinian, n=54) subtypes based on their ability for self-care. Correlations between the relative gray and white matter volumes of the individual cortical Brodmann's areas and five dorsoventral levels of the thalamus were assessed. RESULTS: Compared to normal subjects, schizophrenia patients lacked significant thalamic gray matter volume correlations with the prefrontal and medial temporal cortical regions in the right hemisphere, and with frontal, cingulate, posterior parietal and occipital regions in the left hemisphere, while normal white matter volume cortical-thalamic correlations along the cingulate gyrus and in the temporal lobe were not found in schizophrenia patients in both hemispheres. In contrast to both normal comparison subjects and good-outcome group, schizophrenia patients with poor outcomes showed significant bilateral gray matter volume correlations between the dorsal thalamus and ventral prefrontal cortex, while the group differences in the white matter volume correlations were mostly restricted to the cingulate arch. CONCLUSIONS: Whereas patients with schizophrenia exhibit deficiencies in cortical-thalamic correlational patterns, poor outcome is associated with abnormal interregional correlations not observed in either normal subjects or patients with good outcomes. This latter finding may be explained by a core neurodevelopmental disturbance that results in aberrant cortical-thalamic connectivity in poor-outcome schizophrenia.

Corpus callosum size and diffusion tensor anisotropy in adolescents and adults with schizophrenia.

The corpus callosum has been implicated as a region of dysfunctional connectivity in schizophrenia, but the association between age and callosal pathology is unclear. Magnetic resonance imaging (MRI) and diffusion-tensor imaging (DTI) were performed on adults (n=34) and adolescents (n=17) with schizophrenia and adult (n=33) and adolescent (n=15) age- and sex-matched healthy controls. The corpus callosum was manually traced on each participant׳s MRI, and the DTI scan was co-registered to the MRI. The corpus callosum was divided into five anteroposterior segments. Area and anisotropy were calculated for each segment. Both patient groups demonstrated reduced callosal anisotropy; however, the adolescents exhibited reductions mostly in anterior regions while the reductions were more prominent in posterior regions of the adults. The adolescent patients showed greater decreases in absolute area as compared with the adult patients, particularly in the anterior segments. However, the adults showed greater reductions when area was considered relative to whole brain white matter volume. Our results suggest that the initial stages of the illness are characterized by deficiencies in frontal connections, and the chronic phase is characterized by deficits in the posterior corpus callosum; or, alternatively, adolescent-onset schizophrenia may represent a different or more severe form of the illness.

White matter abnormalities in schizophrenia and schizotypal personality disorder.

Prior diffusion tensor imaging (DTI) studies examining schizotypal personality disorder (SPD) and schizophrenia, separately have shown that compared with healthy controls (HCs), patients show frontotemporal white matter (WM) abnormalities. This is the first DTI study to directly compare WM tract coherence with tractography and fractional anisotropy (FA) across the schizophrenia spectrum in a large sample of demographically matched HCs (n = 55), medication-naive SPD patients (n = 49), and unmedicated/never-medicated schizophrenia patients (n = 22) to determine whether (a) frontal-striatal-temporal WM tract abnormalities in schizophrenia are similar to, or distinct from those observed in SPD; and (b) WM tract abnormalities are associated with clinical symptom severity indicating a common underlying pathology across the spectrum. Compared with both the HC and SPD groups, schizophrenia patients showed WM abnormalities, as indexed by lower FA in the temporal lobe (inferior longitudinal fasciculus) and cingulum regions. SPD patients showed lower FA in the corpus callosum genu compared with the HC group, but this regional abnormality was more widespread in schizophrenia patients. Across the schizophrenia spectrum, greater WM disruptions were associated with greater symptom severity. Overall, frontal-striatal-temporal WM dysconnectivity is attenuated in SPD compared with schizophrenia patients and may mitigate the emergence of psychosis.

A manual, semi-automated and automated ROI study of fMRI hemodynamic response.

This study is a method comparison of three region-of-interest (ROI) tracing approaches. fMRI images acquired during an event-related frequency discrimination task were used in this study. Three [(1) manual, (2) semi-automated, (3) automated] approaches were applied to generate the ROI in the caudate nucleus and extract fMRI hemodynamic response (HR) from the ROI. Less activation with weak and delayed fMRI HR in the caudate were observed in patients than controls by the 3 approaches, but the manual and automated approaches were more sensitive in detecting such fMRI abnormalities. High correlations of the HR measures were found between the manual and semi-automated ROI approaches, suggesting that the semi-automated approach could be used as an alternative to the manual approach in detecting fMRI experimental effect.

fMRI assessment of thalamocortical connectivity during attentional performance.

Functional magnetic resonance imaging (fMRI) studies have shown dysfunction in key areas associated with the thalamocortical circuit in patients with schizophrenia. This study examined the functional connectivity involving the frontal-thalamic circuitry during a spatial focusing-of-attention task in 18 unmedicated patients with schizophrenia and 38 healthy controls. Functional connectivity was analyzed by assigning seed regions (in the thalamic nuclei (mediodorsal nucleus (MDN), pulvinar, anterior nucleus (AN)), the dorsolateral prefrontal cortex (Brodmann areas 9 and 46), and the caudate), and correlating their respective activity with that in the non-seed regions voxel-wise. Functional connectivity analysis demonstrated that functional connectivity was significantly impaired in patients, e.g., between the right pulvinar and regions such as the prefrontal and temporal cortices and the cerebellum. On the other hand, enhanced functional connectivity was found in patients, e.g., between the AN and regions such as the prefrontal and temporal cortices. In addition, the patients had significantly lower task performance and less (but non-significant) brain activation than those of controls. These results revealed disturbed functional integration in schizophrenia, and suggested that the functional connectivity abnormalities in the thalamocortical circuitry, especially the frontal-thalamic circuitry, may underlie the attention deficits in schizophrenia patients. Further, this study suggested that functional connectivity analysis might be more sensitive than brain activation analysis in detecting the functional abnormalities in schizophrenia.

Larger putamen size in antipsychotic-naïve individuals with schizotypal personality disorder.

OBJECTIVE: To (a) compare the size of the dorsal and ventral striatum (caudate and putamen) in a large sample of antipsychotic-naïve individuals with schizotypal personality disorder (SPD) and healthy control participants; (b) examine symptom correlates of striatal size in SPD. METHODS: The left and right caudate and putamen were hand-traced on structural MRI at five dorsal to ventral slice levels in 76 SPD and 148 healthy control participants. A Group×Region (caudate, putamen)×Slice (1-5: ventral, 2, 3, 4, dorsal)×Hemisphere (left, right) mixed-model MANOVA was conducted on size relative to whole brain. RESULTS: Primary results showed that compared with the controls, the SPD group showed (a) larger bilateral putamen size overall and this enlargement was more pronounced at the most ventral and dorsal levels; in contrast, there were no between-group differences in caudate volume; (b) larger bilateral size of the striatum ventrally, averaged across the caudate and putamen. Among the SPD group, larger striatal size ventrally, particularly in the left hemisphere was associated with less severe paranoid symptoms. CONCLUSIONS: Striatal size is abnormal in SPD and resembles that of patients with schizophrenia who respond well to antipsychotic treatment. The results suggest that striatal size may be an important endophenotype to consider when developing new pharmacological treatments and when studying factors mitigating psychosis.