Schizotypal Personality Disorder Symptoms Research Articles

An Overview of Schizotypal Personality Disorder: Etiology Treatment

The article summarizes and analyzes some of the previous studies on schizotypal personality disorder to explain the etiology, genetic aspect such as Catechol-O-methyltransferase (COMT which is situated on chromosome 22q11) and calcium voltage-gated channel subunit alpha1 C (CACNA1C rs1006737); environmental aspect such as risky factors affecting an unnormal brain development like and psychological trauma, and chronic stress, and the treatment (Metacognitive treatment; RuminationFocused Cognitive Behavioral Therapy; Medication treatment) of schizotypal personality disorder are also discussed. Both methods, Metacognitive treatment, and RuminationFocused Cognitive Behavioral Therapy, in their respective cases, improved symptoms in schizotypal personality disorder patients. However, although research on medication treatment shows that although some medicines, like Risperidone and Haloperidol, can also improve schizotypal personality disorder symptoms, they are also accompanied by the side effects. Moreover, the analysis shows that the present research on managing schizotypal personality disorder encounters issues such as insufficient sample size and absence of repeated experiments. These results of prior studies still need further verification before they can be used in practice.

A German translation and validation of the sense of agency scale.

Sense of agency refers to the experience of controlling one's actions and through them events in the outside world. General agency beliefs can be measured with the Sense of Agency Scale (SoAS), which consists of the sense of positive agency subscale (i.e., feeling of being in control over one's own body, mind, and environment) and the sense of negative agency subscale (i.e., feeling existentially helpless). The aim of the present study was to validate a German version of the SoAS. Using factor analyzes, we replicated the two-factor structure of the original version of the SoAS. Further, the German SoAS showed good model fits, good internal consistency, and moderate test-retest reliability. Construct validity was supported by significant low to moderate correlations of the German SoAS with other conceptually similar, but still distinct constructs such as general self-efficacy. Additionally, the German SoAS has an incremental value in explaining variance in the extent of subclinical symptoms of schizotypal personality disorder that goes beyond variance explained by constructs that are conceptually similar to sense of agency. Taken together, the results indicate that the German SoAS is a valid and suitable instrument to assess one's general agency beliefs.

Positive schizotypy, maladaptive openness, and openness facets.

Positive schizotypy includes magical beliefs and unusual perceptual experiences and is highly correlated with the cognitive-perceptual symptoms of schizotypal personality disorder. Increased openness to experience is associated with increased genetic risk for schizophrenia, and it has been commonly thought that positive schizotypy might also be related to increased openness. However, much previous research has failed to identify a sizable association between positive schizotypy and openness. The current research examined whether associations between positive schizotypy and openness might be higher (a) when using measures that more effectively assess the maladaptively high end of openness and (b) for distinct aspects of openness. Participants (n = 672) completed two measures of openness, the Big Five Aspects Scale (BFAS) and Experiential Permeability Index (EPI). We found that associations between positive schizotypy and BFAS-Open were small. However, in item response theory analyses, there was evidence that one facet of the EPI Oddity subscale highly associated with BFAS-Open was more sensitive to the maladaptively high end of openness than BFAS-Open. Further, positive schizotypy was more strongly associated with this EPI facet than with BFAS-Open. In addition, positive schizotypy was especially associated with a second facet of the EPI Oddity subscale. Hence, our study provides further evidence that associations between positive schizotypy and openness increase when assessing the maladaptively high end of openness and that positive schizotypy is most highly associated with particular facets of openness. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

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.

Maternal personality disorder symptoms in primary health care: associations with mother\u2013toddler interactions at one-year follow-up

BackgroundResearch is scarce on how mothers’ symptoms of personality disorders are linked to the mother-toddler relationship. In this study we have explored the extent to which these symptoms are associated with mutual mother-toddler interactions assessed 1 year after the initial assessment.MethodsMothers and their 0–24-month-old children (n = 112) were recruited by nurses at well-baby clinics due to either self-reported or observed mother–toddler interaction problems. At inclusion (T1), mothers filled out the DSM-IV and ICD-10 Personality Questionnaire (DIP-Q), which measures symptoms of ten personality disorders. A year later (T2), mother-toddler interactions were video-recorded and coded using a standardised observation measure, the Emotional Availability Scales.ResultsOnly maternal schizotypal personality disorder symptoms predicted both the mothers’ and the toddlers’ interactional styles. Mothers with schizotypal personality symptoms appeared less sensitive, less structuring and more intrusive in their interactions with their toddlers, while mothers’ borderline personality disorder symptoms were associated with increased hostility. Furthermore, toddlers who had mothers with schizotypal personality symptoms were less responsive towards their mothers.ConclusionMeasured dimensionally by self-report, maternal schizotypal personality symptoms were observed to predict the interaction styles of both mothers and their toddlers in the dyad, while borderline personality disorder symptoms predicted mothers’ interactional behaviour only.Trial registrationCurrent Controlled Trials ISRCTN99793905, retrospectively registered. Registered on (04/08/2014).

Representing schizotypal thinking with dimensional traits: A case for the Five Factor Schizotypal Inventory.

Building on support for the five-factor model (FFM) of personality disorder, the Five Factor Schizotypal Inventory (FFSI) was developed to assess maladaptive traits relevant to schizotypal personality disorder. While the development of the FFSI supports a continuity between schizotypal thinking and perception (STAP) and the FFM domain of Openness to Experience, other studies show inconsistent findings concerning the strength of this relationship. The current study evaluates these relationships by investigating specific components of a short-form of the FFSI (e.g., the FFSI-SF) and 2 other measures of maladaptive traits with the lower order components within commonly employed measures of Openness to Experience. Nomological network similarities were evaluated for the relation of these scales with a series of conceptually relevant variables including intelligence, creativity, and positive schizotypy in a sample of 403 undergraduates, including 102 that were prescreened for elevated symptoms of schizotypal personality disorder (PD). These analyses revealed strong relations across the 3 measures of traits relevant to STAP, supporting the validity of the FFSI-SF. Most notably, 2 specific scales-Multidimensional Personality Questionnaire (MPQ) Absorption and Openness to Fantasy appeared to best capture the core variance across these measures. Furthermore, a nuanced pattern of relations suggested that specific components of STAP (e.g., oddity and fantasy proneness) matched closely with components of Openness to Experience. The results provide additional support for view that schizotypal thinking can be well-captured by personality dimensions that run continuously across normal and pathological levels. (PsycINFO Database Record

PM460. Association between increased resting-state functional connectivity and reduced symptoms of schizotypal personality disorder: neural evidence for compensatory brain responses

PM460. Association between increased resting-state functional connectivity and reduced symptoms of schizotypal personality disorder: neural evidence for compensatory brain responses

Ten-year stability of self-reported schizotypal personality features in patients with psychosis and their healthy siblings

Schizotypal personality disorder (SPD) symptoms or features are common in patients with psychosis and their healthy relatives. However, the long-term stability of these SPD features and therefore their constituting enduring traits underlying vulnerability to psychosis remain to be clarified. Thirty-two patients with psychotic disorders and 29 of their healthy siblings were included from the long-term follow-up study of 89 nuclear families. Participants were clinically assessed by means of a semi-structured diagnostic interview, whereas the Schizotypal Personality Questionnaire-Brief (SPQ-B) was applied for the self-assessment of SPD symptoms. The assessments were carried out upon admission to the study and at follow-up, about 10 years later. The patients had higher scores than their siblings on the SPQ-B both at baseline and follow-up. In addition, self-reported SPD symptoms remained stable over time in total scores and in all the SPQ-B subscores, except for the SPQ-B Disorganization subscale. Self-reported SPD symptoms were stable over the long term among patients with psychotic disorders and their healthy siblings. This finding provides new support for including the SPD construct as a trait measure for studies addressing both vulnerability to psychosis in first-degree relatives of patients with psychosis and long-term persistence of symptoms in patients suffering from psychosis.

Developing psychosis and its risk states through the lens of schizotypy.

Starting from the early descriptions of Kraepelin and Bleuler, the construct of schizotypy was developed from observations of aberrations in nonpsychotic family members of schizophrenia patients. In contemporary diagnostic manuals, the positive symptoms of schizotypal personality disorder were included in the ultra high-risk (UHR) criteria 20 years ago, and nowadays are broadly employed in clinical early detection of psychosis. The schizotypy construct, now dissociated from strict familial risk, also informed research on the liability to develop any psychotic disorder, and in particular schizophrenia-spectrum disorders, even outside clinical settings. Against the historical background of schizotypy it is surprising that evidence from longitudinal studies linking schizotypy, UHR, and conversion to psychosis has only recently emerged; and it still remains unclear how schizotypy may be positioned in high-risk research. Following a comprehensive literature search, we review 18 prospective studies on 15 samples examining the evidence for a link between trait schizotypy and conversion to psychosis in 4 different types of samples: general population, clinical risk samples according to UHR and/or basic symptom criteria, genetic (familial) risk, and clinical samples at-risk for a nonpsychotic schizophrenia-spectrum diagnosis. These prospective studies underline the value of schizotypy in high-risk research, but also point to the lack of evidence needed to better define the position of the construct of schizotypy within a developmental psychopathology perspective of emerging psychosis and schizophrenia-spectrum disorders.

Openness to Experience, Intellect, Schizotypal Personality Disorder, and Psychoticism: Resolving the Controversy

Section III of DSM-5 includes an alternative model for personality disorders comprising five higher-order pathological personality traits, four of which resemble domains from the Big Five/Five-Factor Model of Personality (FFM). There has, however, been considerable debate regarding the association of FFM Openness-to-Experience/Intellect (OE/I) with DSM-5 Psychoticism and Schizotypal Personality Disorder (STPD). The authors identify several limitations in the literature, including inattention to (a) differences in the conceptualization of OE/I in the questionnaire and lexical traditions and (b) the symptom heterogeneity of STPD. They then address these limitations in two large patient samples. The results suggest that OE/I per se is weakly associated with Psychoticism and STPD symptoms. However, unique variance specific to the different conceptualizations of OE/I demonstrates much stronger associations, often in opposing directions. These results clarify the debate and the seemingly discrepant views that OE/I is unrelated to Psychoticism and contains variance relevant to Psychoticism.

Early cannabis use and Schizotypal Personality Disorder Symptoms from adolescence to middle adulthood

BackgroundWhile increasing evidence suggests that cannabis use may play a role in the development of schizophrenia in some young people, less is known about the strength and specificity of its relationship to latent schizophrenia liability, i.e., schizotypal personality disorder traits. AimsDetermine the predictive value of cannabis use during childhood and early adolescence on schizotypal personality disorder (SPD) symptoms projecting into adulthood, using a community-based longitudinal cohort from upstate New York. MethodProspective data from 804 participants was used to determine associations between early cannabis use and later schizotypal symptoms, accounting for important potential confounds (e.g., adolescent schizotypal symptoms). ResultsCannabis use with onset prior to age 14 strongly predicted SPD symptoms in adulthood, independent of early adolescent SPD symptoms, major depression, anxiety disorder, other drug use, and cigarette use. There was no interaction effect of early cannabis use and early adolescent SPD symptoms on SPD symptoms into adulthood. ConclusionsOur data provide further support for a strong association of early cannabis use with the development of symptoms characteristic of schizophrenia spectrum disorders. As with studies in schizophrenia, early SPD symptoms could not fully explain the association of early cannabis use with later schizotypal symptoms. The mechanisms that underlie the association of cannabis use and schizotypal symptoms in a developmental context deserve further exploration.

The differential effects of child abuse and posttraumatic stress disorder on schizotypal personality disorder

Objective Previous findings suggest a relation between trauma exposure and risk for schizotypal personality disorder (SPD). However, the reasons for this relationship are not well understood. Some research suggests that exposure to trauma, particularly early trauma and child abuse, as well as posttraumatic stress disorder (PTSD) may play a role. Methods We examined subjects (n = 541) recruited from the primary care clinics of an urban public hospital as part of an National Institute of Mental Health-funded study of trauma-related risk and resilience. We evaluated childhood abuse with the Childhood Trauma Questionnaire and the Early Trauma Inventory and SPD with the Schedule for Nonadaptive and Adaptive Personality. We assessed for lifetime PTSD using the Clinician-Administered PTSD Scale. Results We found that of the 3 forms of abuse analyzed (emotional, physical, and sexual), only emotional abuse significantly predicted SPD ( P < .001, R = 0.28) when all 3 abuse types were simultaneously entered into a regression model. Lifetime PTSD symptoms also significantly predicted SPD ( P < .001, R = 0.26). Posttraumatic stress disorder was specifically predictive of 4 of the 8 SPD symptoms ( P ≤ .001): excessive social anxiety, a lack of close friends or confidants, unusual perceptual experiences, and eccentric behavior or appearance. Using a Sobel test, we also found a partial mediation effect of PTSD on the relation between emotional abuse and SPD ( z = 3.45, P < .001). Conclusions These findings point to the important influence of emotional abuse on SPD and suggest that PTSD symptoms may provide a link between damaging childhood experiences and SPD symptoms in traumatized adults.

P02-243 - Neurocognition and temperament in borderline and schizotypal personality disorder

ObjectiveExplore the neurocognitive and temperament profile of borderline personality disorder (BPD) and schizotypal personality disorder (SPD) to better understand their underlying neurobiology for improved treatment.Methods17 BPD, 16 SPD, and 15 healthy controls (HCs) were given a comprehensive neuropsychological battery (CANTAB), the Iowa Gambling Task, a time perception task, and questionnaires of impulsivity, temperament, emotion, and frontal behavior (measures orbitofrontal cortex (OFC) dysfunction).ResultsBPD and SPD patients performed significantly worse on the delayed match to sample (DMS) task compared to HCs, but had preserved function on decision-making, planning, time perception and attention tasks. SPD patients performed significantly worse on spatial working memory (SWM) tasks, and had higher religious commitment scores than HC and BPD groups, which correlated with their SWM deficits. BPD patients had significantly more frontal behaviors and emotions than both groups, which correlated with their emotionality, impulsivity, BPD symptoms, and temperament traits.ConclusionsBoth BPD and SPD groups had a deficit on the DMS task, sensitive to medial temporal lobe (MTL) dysfunction, but only SPD patients had SWM deficits, indicative of dorsolateral frontal cortex (DLFC) dysfunction, which correlated with their high religious commitment in line with their odd beliefs and magical thinking. Only BPD patients had frontal behavior deficits, related to OFC dysfunction, which positively correlated with their emotionality, impulsivity, and temperament traits. While both disorders may have a deficit in MTL function, DLFC dysfunction may contribute to SPD symptoms, and OFC dysfunction to BPD symptoms, suggesting treatment should target unique prefrontal cortex regions respectively.

The relationship between interview-based schizotypal personality dimension scores and the continuous performance test

The existing research that has examined cognitive performance in samples with subclinical schizotypal personality features has been largely limited to psychometric self-report questionnaires, which may be biased by distorted self-awareness of symptoms. The present study examined the relationship between performance on a degraded-AX continuous performance test (CPT) and continuous dimension scores created from a structured clinical interview for schizotypal personality disorder (SPD), which reflected both the breadth and severity of schizotypal personality symptoms, in 52 undergraduate students. Only one participant met full diagnostic criteria for SPD. The overall dimension score from the SPD clinical interview showed a positive correlation with both omission (rs=.47) and false alarm (rs=.41) errors on the CPT. Interpersonal symptoms were positively correlated with omission errors (rs=.47), while Disorganized symptoms were positively correlated with false alarm errors (rs=.40). Results suggest that higher SPD interview-based dimension scores are associated with lower levels of performance on the CPT, even when examining a relatively subclinical sample of young adults. In contrast, scores from the psychometric Abbreviated Schizotypal Personality Questionnaire in the same sample did not correlate with accuracy measures on the CPT, suggesting that the interview-based measure of schizotypal personality may have a stronger relationship with CPT accuracy. Findings also add to a growing literature suggesting that Interpersonal SPD symptoms are primarily related to omission errors, while Disorganized SPD symptoms are primarily related to false alarm errors.

Aripiprazole in Schizotypal Personality

Sir: Schizotypal personality disorder (SPD) is characterized by odd, eccentric behavior; inappropriate or constricted affect; odd beliefs or magical thinking; circumstantial, metaphorical, or stereotyped thinking manifested by odd speech; anxiety in social situations; and cognitive or perceptual distortions.1 Studies have been conducted on the efficacy of haloperidol,2 thiothixene,3 olanzapine,4 and risperidone5 in SPD. However, efficacy of aripiprazole in SPD has not been reported. Aripiprazole is a novel antipsychotic with a unique mechanism of action. It is a partial agonist of D2 and D3 dopamine receptors and 5-HT1A serotonin receptors, which are, respectively, responsible for its efficacy on positive, negative, and cognitive symptoms of schizophrenia and its antidepressant and antianxiety actions.6–8 Hence, it is called a dopamine-serotonin system stabilizer.9,10 Aripiprazole has been approved by the U.S. Food and Drug Administration in the treatment of schizophrenia. A search of English-language publications in PubMed using the keywords schizotypal personality disorder and aripiprazole retrieved no published reports or articles. Herein, we describe a patient with SPD of 5 years’ illness duration who had never been treated with any medications and who responded to treatment with aripiprazole. Case report. Mr. A, a 22-year-old engineering student of middle-class socioeconomic status and urban background, presented to our hospital in August 2007 with an insidious onset and continuous course of illness of 5 years’ duration characterized by odd and eccentric behavior, oddities in speech, avoidance of social situations, deteriorating academic performance, idiosyncratic repetitive behaviors, and magical thinking. His family members were concerned about his odd and eccentric behavior, social dysfunction, and academic decline. The above symptoms could not be attributed to any clear-cut psychotic disorders, mood disorders, substance use disorders, or general medical conditions. He had never received treatment for the symptoms. The patient's history and family history were noncontributory. Structured assessment conducted at baseline using the Structured Clinical Interview for DSM-IV Axis I Disorders11 and Structured Clinical Interview for DSM-IV Axis II Personality Disorders12 revealed that Mr. A had schizotypal personality disorder. The Schizotypal Personality Questionnaire (SPQ)13 revealed social anxiety, odd beliefs, odd behaviors, blunted affect, suspiciousness, lack of close friends, and magical thinking. A baseline score of 4 on the Clinical Global Impressions-Severity of Illness scale (CGI-S)14 was noted. Other baseline psychodiagnostic assessments were also conducted, such as the Object Sorting Test, Thematic Apperception Test, and Rorschach Inkblot Test, which revealed the absence of pathognomonic signs of psychosis. After giving informed consent, Mr. A was started on treatment with aripiprazole 10 mg at night. At 2-month (week 8) follow-up, the patient reported a 70% decrease in his symptoms, started attending his engineering college regularly, and showed interest in his studies. His family members reported marked improvement in his social and academic functioning. They also reported that his odd ideas, eccentric behaviors, magical thinking, and suspiciousness were reduced to minimal. His interaction with friends and his mood also improved. His CGI-S score was 3 (mildly ill), and his CGI-Improvement score was 2 (showing much improvement). This patient with SPD had a 5-year duration of untreated illness and was assessed with structured instruments. He responded to treatment with 10 mg of aripiprazole. Currently, thiothixene, haloperidol, risperidone, and olanzapine have been documented to be effective in treatment of SPD. This case report assumes importance in the light of the paucity of aripiprazole studies in SPD. However, the choice of antipsychotic medications is largely based on side effect profile. Available data on aripiprazole reveal that it is an effective medication with a benign adverse effect profile.9,10 Aripiprazole, being a dopamine- serotonin system stabilizer, is hence an ideal drug to target the odd and eccentric behavior, stereotyped thinking, social anxiety symptoms, and obsessive symptoms of SPD. Future double-blind, placebo-controlled studies examining the effectiveness of aripiprazole in the treatment of SPD are needed. Ajay Kumar, M.Phil. Ravikant Pinjarkar, M.Phil. Nitin Anand, M.A., M.Phil. M. Manjula, M.Phil., Ph.D. Department of Mental Health and Social Psychology Suresh Bada Math, M.D., D.N.B., P.G.D.M.L.E. Department of Psychiatry, National Institute of Mental Health and Neurosciences, (Deemed University), Bangalore, India

Eighteen months of drug treatment for depression: Predicting relapse and recovery

Background The clinically relevant outcomes in treating depression are persistent recovery, relapse, and treatment resistance. Method 175 outpatients treated with antidepressants for 6 months were assessed for major depression. Those who had recovered were prospectively monitored for one year to study rates of relapse (at least two weeks of major depression). Those who were depressed at 6 months were monitored for rates of recovery (at least 8 weeks of no major depression). Results 94% of the sample was monitored for one year. Of the 123 patients who were not depressed at 6 months 57 (46%) relapsed. Patients who relapsed were more likely to have a history of recurrent depression, to have residual depressive symptoms, to have a less sustained response to initial treatment, to have avoidant personality disorder symptoms, schizotypal personality disorder symptoms, higher harm avoidance (HA) scores and lower self directedness (SD) scores. Of the 38 patients who were depressed at 6 months 13 (34%) recovered. There were no patient characteristics associated with recovery. Limitations The findings apply to moderately depressed outpatients. There was no placebo control. Conclusion Most patients with depression will recover but many become unwell again within a year. Clinically long term monitoring and sustained efforts to treat patients with major depression seem warranted.

Duration of early maternal separation and prediction of schizotypal symptoms from early adolescence to midlife

Early childhood experiences influence the capacity for healthy social and emotional development. The present study uses longitudinal data to determine whether early maternal separation predicted the subsequent development of schizotypal personality disorder (SPD) symptoms assessed repeatedly from early adolescence over the following 20 years. Within this community sample (N=766), multilevel linear regression analyses revealed the duration of separation from mother in the first 2 years of life predicted elevated SPD symptoms. This relationship was specific to children with mother-reported early angry emotional behavior. These results provide support for the role of early childhood psychosocial risk factors in the development of subsequent schizophrenia spectrum symptoms in emotionally vulnerable children.

Interpersonal problems and emotional intelligence in compulsive hoarding

There is some evidence that compulsive hoarding is associated with social impairment, which may contribute to poor functional outcomes among hoarding patients. In this study, individuals with compulsive hoarding (n = 30) were compared to nonhoarding anxious or depressed patients (n = 30) and nonclinical community participants (n = 30) with respect to clinical characteristics, interpersonal difficulties, and emotional intelligence. All participants were diagnosed using a semi-structured interview and completed self-report measures. Participants with compulsive hoarding endorsed more depression and schizotypal personality disorder symptoms than participants in both comparison groups. Hoarding participants also reported more interpersonal difficulties than community volunteers, but they did not differ significantly from nonhoarding participants with an anxiety or mood disorder. Multiple regression analyses demonstrated that hoarding-related beliefs were marginally related to increased interpersonal problems over and above the effect of depression and anxiety. The groups did not differ significantly with respect to emotional intelligence.

Relative Impact of Young Adult Personality Disorders on Subsequent Quality of Life: Findings of A Community-Based Longitudinal Study

Little is known about long-term prognostic implications of personality disorder (PD) for quality of life (QOL) in the young adult population not selected for psychiatric treatment. The purpose of this study was to determine the association of PDs with QOL assessed after an 11-year interval. PDs were assessed in 1991-1994 at mean age 22, and indicators of QOL were assessed in 2001-2004 at mean age 33 based on a community sample of 588 young adults. Findings indicated that any PD, or a cluster A, B, or C PD each were independently associated with elevated impairment in overall QOL after adjusting for demographic variables, co-occurring Axis I disorder, and physical illness, and PDs in other clusters. Cluster B PD had a greatest adverse impact on QOL. Symptoms of antisocial, borderline, and schizotypal PD symptoms were independently associated with significant reductions in QOL; avoidant, paranoid, and dependent PD symptoms were associated with smaller reductions, not reaching statistical significance. Symptoms of other individual PDs were not associated with reduced QOL. PDs in young adults in the community have an enduring and adverse impact on subsequent QOL that cannot be attributed to physical illness or Axis I psychiatric disorder.

Endophenotypes in the personality disorders

The identification of endophenotypes in the personality disorders may provide a basis for the identification of underlying genotypes that influence the traits and dimensions of the personality disorders, as well as susceptibility to major psychiatric illnesses. Clinical dimensions of personality disorders that lend themselves to the study of corresponding endophenotypes include affective instability, impulsivity, aggression, emotional information processing, cognitive disorganization, social deficits, and psychosis. For example, the propensity to aggression can be evaluated by psychometric measures, interview, laboratory paradigms, neurochemical imaging, and pharmacological studies. These suggest that aggression is a measurable trait that may be related to reduced serotonergic activity. Hyperresponsiveness of amygdala and other limbic structures may be related to affective instability, while structural and functional brain alterations underlie the cognitive disorganization in psychotic-like symptoms of schizotypal personality disorder. Thus, an endophenotypic approach not only provides clues to underlying candidate genes contributing to these behavioral dimensions, but may also point the way to a better understanding of pathophysiological mechanisms.