Revisiting the factor structure for positive and negative symptoms: evidence from a large heterogeneous group of psychiatric patients

OBJECTIVE

The factor structures of individual positive and negative symptoms as well as global ratings were examined in a diagnostically heterogeneous group of subjects.

METHOD

Subjects were identified through a clinical and family study of patients with major psychoses at a VA medical center and evaluated with the Scale for the Assessment of Negative Symptoms and the Scale for the Assessment of Positive Symptoms. For the examination of global-level factor structures (N = 630), both principal-component analysis and factor analysis with orthogonal rotation were used. Factor analysis was used for the examination of item-level factor structures as well (N = 549).

RESULTS

The principal-component analysis of global ratings revealed three factors: negative symptoms, positive symptoms, and disorganization. The factor analysis of global ratings revealed a negative symptom factor and a positive symptom factor. The item-level factor analysis revealed two negative symptom factors (diminished expression and disordered relating), two positive symptom factors (bizarre delusions and auditory hallucinations), and a disorganization factor.

CONCLUSIONS

The generation of additional meaningful factors at the item level suggests that important information about symptoms is lost when only global ratings are viewed. Future work should explore clinical and pathological correlates of the more differentiated item-level symptom dimensions.

Sex differences in neuropsychological function in non-psychotic relatives of schizophrenic probands

Some recent studies suggest that men with schizophrenia may have greater neuropsychological deficits than women. It is not known, however, whether similar sex differences may be present in biological relatives of schizophrenic patients. We evaluated neuropsychological functioning of 54 relatives of schizophrenic patients and 72 normal volunteers. It was hypothesized that, if sex differences were present, they would be accounted for largely by deficits in male relatives. We were particularly interested in three neuropsychological functions that we previously identified as putative neuropsychological vulnerability indicators for schizophrenia: (1) abstraction/executive function; (2) verbal memory; and (3) auditory attention. There were significant group x sex interactions for verbal memory and motor function, and trends toward significant interactions for auditory attention and mental control/encoding. However, with the exception of motor function, it was the female relatives who accounted for most of the impairment. A speculative explanation for the findings is that women may have a higher threshold than men for developing schizophrenia. If so, female relatives might be able to withstand greater impairments than men before developing psychotic symptoms. Consequently, in a sample that was limited to non-psychotic relatives--as in the present study--there could be over-representation of both less impaired men and more impaired women. Alternative explanations and limitations of the study are also discussed.

Pregnancy, delivery and infancy complications and attention deficit hyperactivity disorder: issues of gene-environment interaction

We evaluated the role of pregnancy, delivery, and infancy complications (PDICs) in the etiology of attention deficit hyperactivity disorder (ADHD) and addressed issues of comorbidity and familiarity by testing multiple hypotheses. Subjects were 6-17-year-old boys with DSM-III-R ADHD (n = 140) and normal controls (n = 120) and their first-degree biologic relatives. Information on PDICs was obtained from mothers in a standardized manner blind to the proband's clinical status. Using linear and logistic regression models, a positive association was found between ADHD and PDICs in the probands. Additionally, PDICs were associated with the correlates of ADHD (i.e., impaired cognitive functioning and poor school performance). Moreover, it was those specific complications that reflect chronic exposure, such as maternal bleeding, smoking, family problems, and illicit drug use during pregnancy that accounted for these findings. No interaction between genetic factors and PDICs were found. Our findings add to the literature supporting an association between ADHD and PDICs. Our results may help clinicians focus on particular complications rather than the wide range of possible perinatal complications.

The influence of familial and non-familial factors on the association between major depression and substance abuse/dependence in 1874 monozygotic male twin pairs

The co-occurrence of major depression (MD) with alcohol and illicit substance abuse/dependence (A/D) has been repeatedly observed. However, prior research has been unable to determine whether or not the co-occurrence is a result of familial vulnerability or non-familial influences. The present study examines the association of the lifetime diagnosis of MD with alcohol, cannabis, amphetamine, cocaine, and sedative A/D (DSM-III-R criteria) before and after controlling for familial factors in a non-clinical sample of 1874 middle aged, monozygotic male twin pairs. A lifetime diagnosis of MD was significantly associated with lifetime diagnosis of alcohol and illicit substance A/D prior to accounting for familial factors (odds ratios: 1.8-4.5). After employing a co-twin analytical technique to control for familial factors, a lifetime diagnosis of MD remained significantly associated only with lifetime diagnoses of cannabis, amphetamine and sedative A/D (odds ratios: 2.3-10.9). These results suggest that the association between MD and alcohol A/D is influenced by familial factors. In contrast, the association between MD and illicit substances of A/D is largely explained by non-familial factors.

Models of treatment seeking for alcoholism: the role of genes and environment

We investigated the relative influence of genes and environment on the decision to seek treatment for alcoholism under three models of health care utilization. Lifetime alcohol dependence and two measures of treatment seeking for alcohol problems were determined from a 1992 telephone administration of the Diagnostic interview Schedule. Data were analyzed from 1,864 monozygotic and 1,492 dizygotic male twin respondents from the Vietnam Era Twin Registry. Genetic and environmental contributions to the decision to seek treatment for alcoholism were assessed under competing models for the relationship between genetic influences on alcoholism risk and genetic influences on treatment seeking among those who became alcoholics. Under the best-fitting model, genetic influence accounted for 41% of the variance in treatment seeking and 55% of the liability for alcoholism. Shared environment explained none of the variance in liability for alcoholism, but 40% of the variance in treatment seeking. The severity of alcoholism alone is an inadequate model of treatment seeking, because decisions to seek alcohol treatment are also influenced by substantial genetic and or shared environmental factors unrelated to the determinants of alcoholism.

A prospective four-year follow-up study of children at risk for ADHD: psychiatric, neuropsychological, and psychosocial outcome

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is a familial disorder that places the siblings of ADHD children at high risk for ADHD, conduct, mood, and anxiety disorders. Although the pattern of psychiatric risk has been well documented by prior family studies, neither the short- nor long-term outcome of these high-risk siblings has been prospectively examined.

OBJECTIVE

To document the 4-year psychiatric, psychosocial, and neuropsychological outcome of the siblings of children with ADHD.

METHOD

DSM-III-R structured diagnostic interviews and blind raters were used to conduct a 4-year follow-up of siblings from ADHD and control families. The siblings were also evaluated for cognitive, achievement, social, school, and family functioning.

RESULTS

At follow-up, significant elevations of behavioral, mood, and anxiety disorders were found among the siblings of ADHD children. The high-risk siblings had high rates of school failure and showed evidence of neuropsychological and psychosocial dysfunction. These impairments aggregated among the siblings who had ADHD.

CONCLUSIONS

The siblings of ADHD children are at high risk for clinically meaningful levels of psychopathology and functional impairment. In addition to supporting hypotheses about the familial transmission of ADHD, the results suggest that the high-risk siblings might be appropriate targets for primary preventive interventions.

MRI brain abnormalities in chronic schizophrenia: one process or more?

It has been suggested that schizophrenia is primarily a prefrontal-temporal-limbic circuitry disorder. Further, it has been argued that primary neurologic vulnerability to the illness is established only during early stages of brain development and is not progressive. We tested the hypothesis of whether brain volume losses in prefrontal and temporal-limbic regions have occurred either before or after brain growth was hypothesized to be complete in schizophrenia. Nineteen chronic schizophrenic patients and 19 age- and sex-matched normal controls underwent magnetic resonance imaging (MRI). All scans were segmented into gray and white matter and cerebrospinal fluid (CSF) compartments for the frontal and temporal lobes and posterior cerebral hemispheres. Multivariate analysis of variance was used to analyze absolute intracranial cerebrum and subregion volumes, i.e., gray, white and CSF, absolute tissue (i.e., gray plus white) volumes, and tissue to intracranial volume (TCV) ratios. Patients showed significant intracranial volume reductions only in the frontal lobes but highly significantly lower TCV ratios (i.e., greater relative tissue loss) in all three major regions. It is suggested that the observed decreases in frontal intracranial volumes reflect a pathologic process in schizophrenia that impacted the frontal regions before brain growth was complete. We hypothesize that the generalized lower patient TCV ratios are attributable to a process that affected the whole cerebrum over a time period after brain volume had reached its maximum levels.

Genetics of Alzheimer's disease

We briefly reviewed methods of psychiatric genetics and showed how these have elucidated genetic aspects of Alzheimer's disease. Although some cases of Alzheimer's disease are not familial, clinicians and researchers have identified many families in which the disease occurs in multiple generations in approximately 50% of family members. Linkage analyses have implicated several genes as causes or risk factors for Alzheimer's disease in different families: the amyloid precursor protein gene, the apolipoprotein-E gene (E4 subtype) on chromosome 19, the S182 gene on chromosome 14 and the STM2 gene on chromosome 1. These linkage findings have been replicated in independent laboratories and, thus, provide strong evidence for genetic heterogeneity of this disease. The discovery of these genes may lead to a better understanding of the etiology and pathophysiology of Alzheimer's disease and also raises the possibility of genetic counseling for patients with familial Alzheimer's disease.

The association of antisocial personality symptoms with marijuana abuse/dependence. A monozygotic co-twin control study

This study examines the association of symptoms of lifetime antisocial personality disorder (ASP) with marijuana abuse/dependence in Vietnam-era veteran male monozygotic twin pairs. In 1992, 1,874 monozygotic twin pairs responded to a structured psychiatric interview that obtained data on lifetime history of drug use and ASP. Among randomly selected individuals from each twin pair, 8 of 10 ASP symptoms were significantly more prevalent in persons with a lifetime history of marijuana abuse/dependence compared with those who had never abused any drug (p < .001). Among 99 marijuana discordant twin pairs, however, only two ASP symptoms, "failure to conform to social norms" (odds ratio, 2.8; 95% confidence interval, 1.5 to 5.5) and "reckless regard of own or other's personal safety" (odds ratio, 2.4; 95% confidence interval, 1.0 to 5.4) were significantly increased in marijuana abusing/dependent twins compared with their non-abusing/nondependent twin brother. After adjustment for conduct disorder, alcohol abuse/dependence, and exposure to combat in Vietnam, only "failure to conform to social norms of lawful behavior" (odds ratio, 2.42; 95% confidence interval, 1.12 to 5.21) remained significantly increased in twins with marijuana abuse/dependence.

Genetic influences on DSM-III-R drug abuse and dependence: a study of 3,372 twin pairs

Research and clinical experience indicate that drug use disorders tend to run in families. The objective of this study was to distinguish between the family environment and genetic factors as the source of this observed family resemblance. Data were collected by telephone interview from members of the Vietnam Era Twin Registry, comprising male twin pairs who served in the U.S. military between 1965 and 1975. There were 3,372 pairs in which both twins participated. Drug use disorder was defined as receiving a diagnosis of drug abuse or dependence according to DSM-III-R; 10.1% of the sample had abused or been dependent on at least one illicit drug. A significant difference between concordance rates for monozygotic (26.2%) vs. dizygotic (16.5%) twins indicated a genetic influence on drug use disorder. Biometrical modeling indicated that genetic factors (34% of the variance), the environment shared by twins (28% of the variance), and the nonshared environment (38% of the variance) had significant influences of similar magnitudes on the individual's risk of developing a drug use disorder. These results support the application of molecular genetic approaches to elucidate the genetic influence on drug use disorder, as well as the potential efficacy of environmental intervention to reduce risk.

New phenotype definition of attention deficit hyperactivity disorder in relatives for genetic analyses

The goal of the present investigation was to create a phenotype definition in relatives of probands that reflects a more genetic form of attention deficit hyperactivity disorder (ADHD). Logistic regression was applied to the first-degree relatives of ADHD and normal control probands to create a quantitative phenotype that combined information across psychiatric, cognitive, and demographic domains. Models were run separately in mothers, fathers, sisters, and brothers. Although there was some overlap between the variables retained in each model, no two models had exactly the same variables. Our results suggest that the use of fitted logits may be valuable as a potential index of caseness. Since different characteristics were included in different groups of relatives, our results suggest that gender and generation may moderate the expression of ADHD.

Neuropsychological functioning among the elderly nonpsychotic relatives of schizophrenic patients

In our prior work with a young sample (age < 60), we showed that three neuropsychological functions were impaired among relatives of schizophrenic patients: abstraction, verbal memory, and auditory attention. In the present work we show that these results do not generalize to an older sample aged 60 years and greater. Thus, although we and others have put forth measures of neuropsychological function as indicators of the schizophrenia genotype, the present study suggests that conclusions may be limited to non-elderly samples. Further work is needed to address this issue definitively.

Diagnostic accuracy and confusability analyses: an application to the Diagnostic Interview for Genetic Studies

The dominant, contemporary paradigm for developing and refining diagnoses relies heavily on assessing reliability with kappa coefficients and virtually ignores a core component of psychometric practice: the theory of latent structures. This article describes a psychometric approach to psychiatric nosology that emphasizes the diagnostic accuracy and confusability of diagnostic categories. We apply these methods to the Diagnostic Interview for Genetic Studies (DIGS), a structured psychiatric interview designed by the NIMH Genetics Initiative for genetic studies of schizophrenia and bipolar disorder. Our results show that sensitivity and specificity were excellent for both DSM-III-R and RDC diagnoses of major depression, bipolar disorder, and schizophrenia. In contrast, diagnostic accuracy was substantially lower for subtypes of schizoaffective disorder-especially for the DSM-III-R definitions. Both the bipolar and depressed subtypes of DSM-III-R schizoaffective disorder had excellent specificity but poor sensitivity. The RDC definitions also had excellent specificity but were more sensitive than the DSM-III-R schizoaffective diagnoses. The source of low sensitivity for schizoaffective subtypes differed for the two diagnostic systems. For RDC criteria, the schizoaffective subtypes were frequently confused with one another; they were less frequently confused with other diagnoses. In contrast, the DSM-III-R subtypes were often confused with schizophrenia, but not with each other.

Assessing risk for the Tourette spectrum of disorders among first-degree relatives of probands with Tourette syndrome

Previous studies have indicated that genetic investigations of Tourette syndrome (TS) should focus on a phenotype that includes not only TS, but chronic tics (CT) and obsessive-compulsive disorder (OCD) as well. These studies have shown that sex may play a role in determining which of the disorders in the TS spectrum is expressed in a susceptible individual. Female relatives of TS probands far more often express OCD, while male relatives more often express TS or CT. Data from the Yale Family Study of TS were used to model risk to first-degree relatives of probands with TS for a variety of TS disease phenotypes. Risk to relatives was modeled using multivariate Cox regression analysis, a method appropriate for assessing risk when there is correlation among disease onsets. This is the first known application of this method to family data. The study identified two proband characteristics that increase the risk for disease onset among both male and female relatives for all TS spectrum disorders, lending credence to the hypothesis that TS spectrum disorders share a common etiology. These were a relatively younger age-at-onset, and no experience of simple motor tics. The predictive ability of two additional factors varied by both sex and disease phenotype. These characteristics, i.e., proband onset with compulsive tics, and proband onset with range, appear to increase risk primarily in female relatives, and for the OCD part of the spectrum.

Mortality among patients with schizophrenia

Results from a 40-year followup study of psychotic patients are presented to illustrate some of the major findings and unanswered questions about excess mortality in schizophrenia and to suggest analytical approaches that take full account of the potential effects of sample heterogeneity. In this study, hospital-diagnosed schizophrenia patients were at increased mortality risk whether or not they met research criteria for schizophrenia. In addition, mortality outcomes of several major diagnostic groups were similar despite substantial clinical and demographic differences between the groups at baseline. These results suggest that both diagnosis-specific and nondiagnostic factors are needed to account for excess mortality in patients with major psychiatric disorders. The issue of heterogeneity is also crucial for the clinical purposes of predicting and ultimately reducing the mortality risk of psychiatric patients, for example, in delineating profiles of high-risk patients who are not necessarily typical of other patients with the same diagnosis.

Genetic heterogeneity may in part explain sex differences in the familial risk for schizophrenia

The purpose of this study was to attempt, in part, to explain significant sex differences in the familial risk (FMR) for schizophrenia found in previous studies. We hypothesized that, like probands, relatives of male vs. female probands may express different forms or subsyndromal symptoms of schizophrenia, i.e., differential expression of flat affect. Studied were 332 schizophrenic probands defined by Diagnostic and Statistical Manual of Mental Disorders, 3rd ed. (DSM-III), criteria and 725 first-degree relatives from well-known retrospective cohort family studies. Results showed that relatives of male probands were at significantly higher risk for expressing flat affect than relatives of female probands, which did not hold for relatives of normal controls. Logistic regression was used to show that when flat affect was incorporated into the definition of affected among relatives, sex differences in FMR disappeared.

Attention deficit hyperactivity disorder and comorbid disorders: issues of overlapping symptoms

OBJECTIVE

Since some symptoms are shared by both attention deficit hyperactivity disorder (ADHD) and comorbid psychiatric conditions, it is possible that a diagnosis of ADHD is an artifact of the overlapping symptoms. This article focuses on the assessment of the influence of overlapping symptoms on the diagnosis of ADHD.

METHOD

Three groups of subjects were studied: a group of clinically referred children and adolescents, a group of nonreferred adults who were the parents of these children and adolescents, and a group of clinically referred adults with ADHD. The authors assessed the extent of symptom overlap between ADHD and the disorders that frequently co-occur with ADHD; major depression, bipolar disorder, and generalized anxiety disorder. To determine the degree to which this symptom overlap influences these diagnoses, each individual was rediagnosed on the basis of two different techniques that corrected for the overlapping symptoms, a subtraction method and a proportion method.

RESULTS

The majority of subjects who had both ADHD and a comorbid psychiatric disorder maintained their diagnosis of ADHD when the overlapping symptoms were subtracted. Moreover, when overlapping ADHD symptoms were subtracted, on average, 79% maintained their diagnosis of major depression, 56% maintained their diagnosis of bipolar disorder, and 75% maintained their diagnosis of generalized anxiety disorder.

CONCLUSIONS

These findings show that ADHD is not an artifact of symptoms shared with other psychiatric disorders and that the comorbid conditions themselves are not an artifact of overlapping ADHD symptoms.

Differential heritability of adult and juvenile antisocial traits

BACKGROUND

Studies of adult antisocial behavior or criminality usually find genetic factors to be more important than the family environment, whereas studies of delinquency find the family environment to be more important. We compared DSM-III-R antisocial personality disorder symptoms before vs after the age of 15 years within a sample of twins, rather than comparing across studies.

METHODS

We administered the Diagnostic Interview Schedule Version III-revised by telephone to 3226 pairs of male twins from the Vietnam Era Twin Registry. Biometrical modeling was applied to each symptom of antisocial personality disorder and summary measures of juvenile and adult symptoms.

RESULTS

Five juvenile symptoms were significantly heritable, and five were significantly influenced by the shared environment. Eight adult symptoms were significantly heritable, and one was significantly influenced by the shared environment. The shared environment explained about six times more variance in juvenile anti-social traits than in adult traits. Shared environmental influences on adult antisocial traits overlapped entirely with those on juvenile traits. Additive genetic factors explained about six times more variance in adult vs juvenile traits. The juvenile genetic determinants overlapped completely with genetic influences on adult traits. The unique environment (plus measurement error) explained the largest proportion of variance in both juvenile and adult antisocial traits.

CONCLUSIONS

Characteristics of the shared or family environment that promote antisocial behavior during childhood and early adolescence also promote later antisocial behavior, but to a much lesser extent. Genetic causal factors are much more prominent for adult than for juvenile antisocial traits.

The case for heterogeneity in the etiology of schizophrenia

To confirm etiological heterogeneity, it is required that schizophrenic patients may be separated into at least two classes having different known etiologies and, perhaps, different pathophysiological signatures. In contrast, the homogeneity hypothesis asserts that there is a single necessary and sufficient cause or configuration of causes of schizophrenia. Because the link between phenotypic heterogeneity and etiological heterogeneity is tenuous, attempts to use purely phenotypic data to infer etiologic heterogeneity must be viewed cautiously. We examined three candidate causes for schizophrenia: genes, obstetric complications and viral infection. Cytogenetic studies show that some rare cases of schizophrenia are due to gross abnormalities of chromosomes. As for the large majority of schizophrenic patients, the candidate cause data most certainly reject the most parsimonious version of the hypothesis of etiological homogeneity: that all schizophrenia is caused by exactly the same pattern of genetic mutations, birth related complications and exposure to the same viral infections. We conclude that the heterogeneity debate should consider the possibility of rewording the question: 'Heterogeneity: yes or no?' to 'Heterogeneity: how much?'

Diagnostic accuracy and linkage analysis: how useful are schizophrenia spectrum phenotypes?

OBJECTIVE

Numerous studies suggest that the nonschizophrenic relatives of schizophrenic patients exhibit psychiatric and other features that discriminate them from normal comparison subjects. These features have been put forth as "spectrum" phenotypes that may be variant manifestations of the schizophrenia genotype. However, most of these studies do not address a key measurement question: does the diagnostic accuracy of these spectrum classifications warrant their use in genetic linkage studies of schizophrenia?

METHOD

The authors reviewed 30 studies of putative indicators of the schizophrenic genotype: schizotypal personality disorder, eye tracking dysfunction, attentional impairment, auditory evoked potentials, neurological signs, neuropsychological impairment, and allusive thinking.

RESULTS

Although each of 42 measures of these indicators discriminated the relatives of schizophrenic patients from the normal comparison subjects, a diagnostic accuracy analysis suggested that only six of these would improve the informativeness of genetic linkage data.

CONCLUSIONS

Many proposed spectrum phenotypes for schizophrenia may not be useful for linkage analysis because of high false positive rates (poor specificity). Future work aimed at describing and developing phenotypes for linkage analysis should assess the diagnostic accuracy of proposed measures.

Neuropsychological functioning among the nonpsychotic relatives of schizophrenic patients: a diagnostic efficiency analysis

Numerous studies suggest that the relatives of schizophrenic patients exhibit neuropsychological impairments that are milder yet similar to those seen among schizophrenic patients. The authors assessed 35 nonpsychotic relatives of schizophrenic patients and 72 normal controls using a clinical and experimental neuropsychological test battery. Three neuropsychological functions met criteria for risk indicators of the schizophrenia genotype: abstraction, verbal memory, and auditory attention. These findings could not be attributed to parental socioeconomic status, education, general visual-spatial ability, or psychopathology. Furthermore, exploratory analyses were performed to determine whether the diagnostic efficiency of the indicators could be adjusted to meet the needs of genetic linkage analyses. These analyses suggest that psychometric considerations may help to create measures for genetic linkage studies.

Correlates of psychosis proneness in relatives of schizophrenic patients

The Magical Ideation Scale (MIS), Perceptual Aberration Scale (PABS), Social Anhedonia Scale (SAS), and Physical Anhedonia Scale (PAS) were administered to 98 relatives of schizophrenic patients along with a measure of personality disorders (the Personality Diagnostic Questionnaire--Revised). Hierarchical regression analysis indicated that the schizotypal and borderline personality disorder (PD) scales explained significant variance in both the MIS and PABS; the avoidant PD scale also explained significant variance in the PABS. The schizoid, paranoid, and avoidant PD scales explained significant variance in the SAS. Sibling intraclass correlations indicated a significant heritability of 0.62 for the PABS.