Studies examining the neurocognitive and circuit-based etiology of psychiatric illness are moving toward inclusive, global designs. A potential confounding effect of these associations is general intelligence; however, an internationally validated, harmonized intelligence quotient (IQ) measure is not available. We describe the procedures used to measure IQ across a five-site, multinational study and demonstrate the harmonized measure’s cross-site validity. Culturally appropriate intelligence measures were selected: four short-form Wechsler intelligence tests (Brazil, Netherlands, South Africa, United States) and the Binet Kamat (India). Analyses included IQ scores from 255 healthy participants (age 18–50; 42% male). Regression analyses tested between-site differences in IQ scores, as well as expected associations with sociodemographic factors (sex, socioeconomic status, education) to assess validity. Harmonization (e.g., a priori selection of tests) yielded the compatibility of IQ measures. Higher IQ was associated with higher socioeconomic status, suggesting good convergent validity. No association was found between sex and IQ at any site, suggesting good discriminant validity. Associations between higher IQ and higher years of education were found at all sites except the United States. Harmonized IQ scores provide a measure of IQ with evidence of good validity that can be used in neurocognitive and circuit-based studies to control for intelligence across global sites.

Patients with predominantly unilateral parkinsonian signs may provide a unique opportunity to evaluate the cerebral representation of cognitive functions characteristically affected in idiopathic Parkinson’s disease. Twenty hemiparkinsonian patients (ten left and ten right) and 10 healthy controls, matched for age and education, were studied with neuropsychological tests and positron emission tomography. Both right and left hemiparkinsonians evidenced impairments in visuospatial and verbal episodic memory function, but had no deficits in executive abilities, compared to controls. None of the neuropsychological test scores distinguished right from left hemiparkinsonians. Glucose metabolic profiles were identical for the three groups in all cortical areas assessed; in the subcortex however, lenticular hypermetabolism contralateral to the predominant side of motor involvement was evident in the left hemiparkinsonian group. Correlational analysis revealed that higher glucose metabolic rates in the basal ganglia of these hemiparkinsonians were associated with lower visuospatial test scores. In frontal and parietal cortex, decreasing glucose metabolism was positively associated with neurobehavioral function; in temporal cortex, measures of attention and memory decreased with increasing glucose metabolic rates.

In this article, we review attempts to account for the thought disorder present in some schizophrenic patients in terms of cognitive deficits in the domains of working memory, attention, language, and semantic memory. Although each psychological construct can account for some of the data described here, establishment of a primary cognitive impairment responsible for thought disorder is not forthcoming, perhaps due to its underlying multidimensional pathology. While the relationship of working memory, attention, and language processing to thought disorder is ambiguous, semantic memory is emerging as a promising construct, that may yield insight into cognitive mechanisms that underlie thought disorder and neuroleptic responsiveness.

Learning and memory were assessed in 24 monozygotic (MZ) pairs of individuals discordant for schizophrenia or delusional disorder and seven normal pairs of MZ twins. On declarative memory tasks, the affected group displayed a pattern that might best be characterized as dysmnesic in that they performed significantly worse than the discordant unaffected group on story recall, paired associated learning, and visual recall of designs, but they learned over time, had relatively preserved recognition memory, and did not show profoundly accelerated rates of forgetting. Effortful, volitional retrieval from the lexicon, measured by verbal fluency, was also compromised in the affected group. On the other hand, procedural learning of the motor skill in a pursuit rotor task was relatively intact in the affected group. Comparisons of the normal group and unaffected group indicated that the latter group had very mild impairments in some aspects of episodic memory, namely, immediate and delayed recall of stories and delayed recall of designs. It is highly unlikely that the impairments observed in the affected group can be attributed to differences in genome, family environment, socioeconomic circumstance, or educational opportunity, as all of these were controlled by the twin paradigm. Rather, the impairments appear to be related to the intercession of disease. The neuropsychological profile is consistent with frontal lobe and medial temporal lobe dysfunction, as noted in this sample as well as other samples of schizophrenic singletons. Significant correlations between many measures of memory and global level of social and vocational functioning within the discordant group were also found. Thus difficulties in rapidly acquiring new information and propitiously retrieving old information may burden patients with schizophrenia in many of the transactions of everyday life.

There has been increasing interest in the semantic cognitive system in schizophrenia. Recent findings suggest a possible breakdown of semantic information processing in this disorder. The current study attempts to further examine semantic organization in schizophrenia. Twenty-eight chronic, early-onset schizophrenic patients and 32 controls were matched for prcmorbid intelligence and compared in their ability to spontaneously cluster exemplars from a specific category during a fluency task. Using multidimensional scaling and clustering techniques, 11 exemplars occurring most frequently in both groups were chosen for examination of their relative “proximity” during word generation. Patients with schizophrenia showed a less stable two-dimensional organization of exemplars and were less likely to group exemplars into subordinate clusters than were normals. These results suggest that semantic networks arc disorganized in these patients. These findings may have some implications for the debate over the origin of “thought disorder” in schizophrenia. (JINS, 1996, 2, 267–273.)

Background. The close association between generalized anxiety disorder (GAD) and major depressive disorder (MDD) prompts questions about how to characterize them in future diagnostic systems. We tested whether risk factors for MDD and GAD are similar or different.

Method. The representative 1972–73 Dunedin birth cohort of 1037 males and females was followed to age 32 with 96% retention. Adult GAD and MDD were diagnosed at ages 18, 21, 26, and 32 years, and juvenile anxiety/depression were also taken into account. Thirteen prospective risk measures indexed domains of family history, adverse family environment, childhood behavior, and adolescent self-esteem and personality traits.

Results. Co-morbid MDD+GAD was antedated by highly elevated risk factors broadly across all domains. MDD+GAD was further characterized by the earliest onset, most recurrence, and greatest use of mental health services and medication. Pure GAD had levels of risk factors similar to the elevated levels for co-morbid MDD+GAD; generally, pure MDD did not. Pure GAD had risks during childhood not shared by pure MDD, in domains of adverse family environment (low SES, somewhat more maltreatment) and childhood behavior (internalizing problems, conduct problems, somewhat more inhibited temperament). Pure MDD had risks not shared by pure GAD, in domains of family history (of depression) and personality (low positive emotionality).

Conclusions. Specific antecedent risk factors for pure adult MDD versus GAD may suggest partly different etiological pathways. That GAD and co-morbid MDD+GAD share many risk markers suggests that the presence of GAD may signal a pathway toward relatively more severe internalizing disorder.

The issue of progressive cognitive decline in patients with schizophrenia has been debated. We performed a cross-sectional study of patients with chronic schizophrenia, aged from 18 to 69 years, in order to address this issue. The patients included in this study passed a rigorous screen for any comorbid condition with an adverse impact on central nervous system function. We assessed intellectual deterioration with a battery of neuropsychological tests known to be sensitive to cognitive impairment in progressive dementia. No evidence of accelerated intellectual decline was found. No significant differences were found between the five age-derived cohorts (18–29, 30–39, 40–49, 50–59, and 60–69 years of age) on the Mini-Mental State Examination, Dementia Rating Scale, or other tests sensitive to dementia. While performance on the Boston Naming Test significantly declined with age, this was mainly due to age rather than duration of illness. However, it is important to note that mean performances on the majority of the tests were abnormal across all cohorts studied. These results suggest that intellectual function does not markedly decline during the adulthood of patients with schizophrenia. The course of schizophrenia is more consistent with a static encephalopathy than a dementing disorder.

Psychiatric symptoms and cognition were assessed in 13 patients with schizophrenia, one patient with schizoaffective disorder, and one patient with psychosis not otherwise specified while they received a conventional neuroleptic and again after an average of 15 months on clozapine. Despite improvements in psychiatric symptoms, attention, memory, and higher-level problem-solving were essentially unchanged. This suggests that certain cognitive deficits are relatively independent of psychotic symptoms in schizophrenia, and are probably central and enduring features of the disorder. Cognitive disability appeared to have been rate-limiting in the sample's rehabilitation, as patients' social and vocational adjustment remained marginal during the study. We also observed that treatment with clozapine was associated with a decline in some memory functions; the potent anticholinergic properties of the drug may have been responsible for this.

Thirty-nine patients with DSM–III diagnoses of schizophrenia were examined for age disorientation, an inability to produce one's correct chronological age upon request. Six patients were age-disoriented and demented (as defined by Mini-Mental State evaluation), while two patients had delusions concerning their age, but were not demented. Age-disoriented, demented patients had very large cerebral ventricles and very low Mini-Mental State scores. This group differed on the cognitive and neuroanatomic variables from other demented, but not age-disoriented, patients, as well as from non-demented patients who were age-oriented. The age-disoriented patients appeared to be at an extreme end of the dementia spectrum in schizophrenia.