Are there sex differences in neuropsychological functions among patients with schizophrenia?

Cognitive performance in schizophrenia: relationship to regional brain volumes and psychiatric symptoms

In an all-male sample of schizophrenic patients stabilized by medication (n=62) and normal controls (n=27), we obtained neuropsychological test data and high-resolution whole brain magnetic resonance scans, as well as detailed psychiatric rating scales on a subset of the patients (n=47). Schizophrenic patients had significantly worse overall age-adjusted cognitive performance than normal controls (average z-score=-0.90, range=-0.60 to -1.81), which included relatively more severe deficits with different types of memory, psychomotor speed, verbal fluency and verbal abstraction. Schizophrenic patients also had significantly smaller bilateral volumes in gray but not white matter in the prefrontal region, superior temporal gyrus and whole temporal lobe, but no group differences were observed in the hippocampus and parahippocampus. Correlations between the brain regions and cognitive performance revealed different sets of significant relationships for the two groups, particularly in the prefrontal and hippocampal regions. In addition, inverse correlations were observed between certain cognitive abilities (psychomotor speed, cognitive flexibility and verbal fluency) and patients' psychiatric ratings, especially with measures of negative symptoms. The convergence of findings for schizophrenic patients regarding the prefrontal region, negative symptoms, psychomotor speed and cognitive flexibility suggests that schizophrenic negative symptoms may involve disruption of frontal-subcortical connections.

Gender-specific molecular heterosis of dopamine D2 receptor gene (DRD2) for smoking in schizophrenia

We examined the genetic effect of DRD2 A1 allele in 167 Korean schizophrenics in relation to their smoking habit. Although there was no apparent difference in the genotype distributions of DRD2 gene among the female schizophrenics (n = 66), the male counterpart (n = 101) showed significant differences in their genotype distributions. The comparison between male smoking and non-smoking patients showed the difference in genotype distribution (P = 0.010) with a higher prevalence of A1 allele (P = 0.020) and frequency of heterozygotes (P = 0.005), but not frequency of the A1 allele. The A1A2 heterozygotes male showed significantly higher smoking rate compared to the A1A1 or A2A2 homozygotes male, and non-smokers were deficient in heterozygotes. By contrast, among female schizophrenics, the heterozygotes showed a lower smoking rate than homozygotes and there were more heterozygotes in non-smokers. The deviation from Hardy-Weinberg expectations was observed in male and female non-smokers showing quite opposite profiles. Highly significant differences were seen between male and female non-smokers in A1 prevalence (P = 0.001), genotype distribution (P = 0.00011), and frequency of heterozygotes (P = 0.00003), but not in A1 frequency. The analyses from both male and female as one group showing no significant difference in the genotype distributions between smokers and non-smokers could be explained by the gender difference in the genetic effect of DRD2 A1 allele. Our findings present the gender-specific molecular heterosis of DRD2 gene in relation specifically to the smoking status of schizophrenic patients. They indicate the importance of heterosis and gender effects that should be taken into consideration for the association studies.

Sex differences in clinical response to olanzapine compared with haloperidol

There is current disagreement over whether men and women respond differently to typical or atypical antipsychotic medications. This study reanalyzed a large international clinical trial of olanzapine (Olz) compared with haloperidol (Hal) to test for sex differences in treatment response, controlling for illness chronicity and menopausal status. We hypothesized that women would show a greater response to either medication than men, particularly among first admission, premenopausal women. DSM-III-R schizophrenia inpatients (700 women and 1295 men) were randomly assigned to a 6-week trial of Olz vs. Hal. Longitudinal random effect models were used to test for interactions of sex with medication, chronicity and menopausal status on treatment response. Findings showed that women on olanzapine had a greater drop in overall symptomatology by week 4 than any other group, and their level of symptomatology remained lower throughout the 6-week trial. The sex differences in treatment response in olanzapine compared with haloperidol were, in part, dependent on chronicity and, in women, menopausal status. That is, first episode women on haloperidol exhibited an increase in symptomatology over the 6-week trial compared to their male counterparts, while multiply hospitalized women had a better treatment response on haloperidol than their male counterparts. Women on olanzapine had a significantly better treatment response than men, regardless of chronicity. Finally, premenopausal women had a significantly better treatment response than postmenopausal women, regardless of treatment and chronicity.

A comparative profile analysis of neuropsychological functioning in patients with schizophrenia and bipolar psychoses

Evidence for neuropsychological deficits in schizophrenia is substantial whereas evidence for the specificity of dysfunction is relatively sparse. To assess specificity, we compared neuropsychological function in patients with chronic schizophrenia, patients with chronic psychotic bipolar disorder and normal controls. Groups were comparable on age, ethnicity and expected intellectual ability (based on single word reading). Patients with schizophrenia and bipolar psychoses were also relatively similar on age at onset and number of hospitalizations. Using multivariate analyses of variance with sex and parental SES as covariates (our primary analyses), patients with schizophrenia were significantly more impaired than controls on seven of eight neuropsychological functions (all but verbal ability), and were significantly more impaired than bipolar patients on abstraction, perceptual-motor speed and vigilance. Bipolar patients were significantly impaired compared to controls on declarative verbal memory, and showed moderate-to-large effect size decrements on abstraction, perceptual-motor speed and vigilance. Results were not attenuated when IQ was controlled, which was significantly lower in patients with schizophrenia. Analyses indicated that the two psychiatric groups had similar profile patterns, but that patients with schizophrenia had a more severe impairment than patients with bipolar psychoses. Further research is required to determine whether similar mechanisms underly the neurocognitive deficits in these disorders.

Intelligence quotient and neuropsychological profiles in patients with schizophrenia and in normal volunteers

BACKGROUND

The objective of this study was to examine neuropsychological performance at different intelligence quotient (IQ) levels in schizophrenia.

METHODS

Thirty-six patients with schizophrenia were matched with 36 normal control subjects in two IQ groups: low average (81-94) and average (95-119). Performance level (IQ group main effects) and profile shape (IQ group x function interactions) were compared.

RESULTS

Current IQ was lower than estimated premorbid intellectual ability in both patient groups. Patients also displayed poorer neuropsychological function than same-IQ control subjects, suggesting neuropsychological dysfunction beyond their already compromised IQ. Patients had different profile shapes than control subjects, but profile shapes were consistent within patients and control subjects at each IQ level. Patients at both levels had higher verbal and lower performance IQ than control subjects. Abstraction-executive function was one of the lowest neuropsychological scores in both patient groups. Average IQ patients had nonsignificantly better overall neuropsychological performance than low average control subjects, but the effect size (.43) was quite small relative to the IQ difference (effect size = 2.57).

CONCLUSIONS

Neuropsychological patterns in schizophrenia tend to be consistent at different IQ levels. Even schizophrenia patients with normal current IQs manifest substantial neuropsychological compromise relative to their level of general intellectual ability. The results strengthen the argument that neurocognitive deficits are core deficits of schizophrenic illness.

Neuroprotection by estradiol

This review highlights recent evidence from clinical and basic science studies supporting a role for estrogen in neuroprotection. Accumulated clinical evidence suggests that estrogen exposure decreases the risk and delays the onset and progression of Alzheimer's disease and schizophrenia, and may also enhance recovery from traumatic neurological injury such as stroke. Recent basic science studies show that not only does exogenous estradiol decrease the response to various forms of insult, but the brain itself upregulates both estrogen synthesis and estrogen receptor expression at sites of injury. Thus, our view of the role of estrogen in neural function must be broadened to include not only its function in neuroendocrine regulation and reproductive behaviors, but also to include a direct protective role in response to degenerative disease or injury. Estrogen may play this protective role through several routes. Key among these are estrogen dependent alterations in cell survival, axonal sprouting, regenerative responses, enhanced synaptic transmission and enhanced neurogenesis. Some of the mechanisms underlying these effects are independent of the classically defined nuclear estrogen receptors and involve unidentified membrane receptors, direct modulation of neurotransmitter receptor function, or the known anti-oxidant activities of estrogen. Other neuroprotective effects of estrogen do depend on the classical nuclear estrogen receptor, through which estrogen alters expression of estrogen responsive genes that play a role in apoptosis, axonal regeneration, or general trophic support. Yet another possibility is that estrogen receptors in the membrane or cytoplasm alter phosphorylation cascades through direct interactions with protein kinases or that estrogen receptor signaling may converge with signaling by other trophic molecules to confer resistance to injury. Although there is clear evidence that estradiol exposure can be deleterious to some neuronal populations, the potential clinical benefits of estrogen treatment for enhancing cognitive function may outweigh the associated central and peripheral risks. Exciting and important avenues for future investigation into the protective effects of estrogen include the optimal ligand and doses that can be used clinically to confer benefit without undue risk, modulation of neurotrophin and neurotrophin receptor expression, interaction of estrogen with regulated cofactors and coactivators that couple estrogen receptors to basal transcriptional machinery, interactions of estrogen with other survival and regeneration promoting factors, potential estrogenic effects on neuronal replenishment, and modulation of phenotypic choices by neural stem cells.

Gender differences in premorbid cognitive performance in a national cohort of schizophrenic patients

Despite significant research, there are still inconsistent findings regarding gender differences in cognitive performance in individuals already diagnosed with schizophrenia; studies have found that males suffering from schizophrenia are more, less or equally impaired compared with females. Gender differences in cognitive performance in individuals suffering from schizophrenia may be influenced by gender differences in premorbid cognitive performance; the very few and very small N studies published indicated that males have a poorer pre-morbid cognitive performance than females. This study examined the gender differences in premorbid cognition, utilizing cognitive assessments performed on female and male adolescents before induction into military service. The Israeli Draft Board Registry, which contains cognitive assessments equivalent to IQ scores on 16-18 year old Israeli adolescents, was linked with the Israeli National Psychiatric Hospitalization Case Registry, which records all psychiatric hospitalizations in the country. Scores on premorbid cognitive performance in schizophrenia were examined in 90 female-male case pairs matched for school attended as a proxy for socio-economic status. The mean age of first hospitalization was 20. 1+/-1.8 years of age for males and 19.6+/-1.8 years of age for females. A repeated-measures ANCOVA with age of first hospitalization and years of formal education as covariates, and controlling for gender differences in cognitive performance in healthy adolescents, revealed a significant difference in pre-morbid cognitive performance between males and females on all four cognitive measures [F(1,87)=8.07, P=0.006] with females scoring lower (worse) than males. In this national cohort, pre-morbid cognition was poorer in female, compared with male, adolescents who will suffer from schizophrenia in the future, a result consistent with some, but not all, similar studies. These results may be valid only for patients with first hospitalization around age 20. Hence, gender differences in premorbid cognition should be taken into account when assessing gender differences in cognition in schizophrenia.

Age and neuropsychologic function in schizophrenia: a decline in executive abilities beyond that observed in healthy volunteers

BACKGROUND

Kraepelin originally conceptualized schizophrenia as a degenerative brain disorder. It remains unclear whether the illness is characterized by a static encephalopathy or a deterioration of brain function, or periods of each condition. Assessments of cognitive function, as measured by neuropsychologic assessment, can provide additional insight into this question. Few studies of patients with schizophrenia have investigated the effect of aging on executive functions, in an extensive neuropsychologic battery across a wide age range, compared to healthy volunteers.

METHODS

We examined the interaction of aging and neuropsychologic function in schizophrenia through a cross-sectional study in patients (n = 87) and healthy control subjects (n = 94). Subjects were divided into three age groups (20-35, 36-49, and 50-75), and performance on an extensive neuropsychologic battery was evaluated.

RESULTS

Compared to control subjects, patients with schizophrenia demonstrated similar age-related declines across most neuropsychologic functions, with the exception of abstraction ability, in which significant evidence of a more accelerated decline was observed.

CONCLUSIONS

These results are consistent with previous reports indicating similar age effects on most aspects of cognition in patients with schizophrenia and healthy adults, but they support the hypothesis that a degenerative process may result in a more accelerated decline of some executive functions in older age in schizophrenia.

Reduced anterior cingulate gyrus volume correlates with executive dysfunction in men with first-episode schizophrenia

Although frontal lobe structural and functional abnormalities have been identified in schizophrenia, their relationship remains elusive. Because the frontal lobes are both structurally and functionally heterogeneous, it is possible that some measures of frontal lobe structure may not have accurately identified relevant frontal lobe subregions. The authors hypothesized that the volumes of two dorsal, 'archicortical' subregions (i.e. superior frontal gyrus and anterior cingulate gyrus), but not a ventral, 'paleocortical' subregion (i.e. orbital frontal region) would be significantly and selectively correlated with executive and motor dysfunction in patients with schizophrenia as previously reported for the anterior hippocampal region. Volumes of these frontal lobe subregions were measured from magnetic resonance images based on sulcal anatomy in 20 men and 15 women with first-episode schizophrenia. All patients completed a comprehensive neuropsychological test battery while clinically stabilized that encompassed six domains of functioning: attention, executive, motor, visuospatial, memory and language. Findings indicated that reduced anterior cingulate gyrus volume was significantly correlated with worse executive functioning in men; among women, there were no significant correlations. Among men, anterior cingulate gyrus volume was significantly more strongly correlated with executive functioning than with attention, visuospatial, memory, language and general intellectual functioning. Neither executive nor motor functioning was significantly more strongly correlated with the dorsal 'archicortical' volumes than with orbital frontal volume. These findings suggest a link between executive deficits and dysfunction of the dorsal 'archicortical' system and implicate sex differences in their relationship in first-episode schizophrenia.

Verbal and nonverbal neuropsychological test performance in subjects with schizotypal personality disorder

OBJECTIVE

The authors contrasted verbal and nonverbal measures of attention and memory in patients with DSM-IV-defined schizotypal personality disorder in order to expand on their previous findings of verbal learning deficits in these patients and to understand better the neuropsychological profile of schizotypal personality disorder.

METHOD

Cognitive test performance was examined in 16 right-handed men who met diagnostic criteria for schizotypal personality disorder and 16 matched male comparison subjects. Neuropsychological measures included verbal and nonverbal tests of persistence, supraspan learning, and short- and long-term memory retention. Neuropsychological profiles were constructed by standardizing test scores based on the means and standard deviations of the comparison subject group.

RESULTS

Subjects with schizotypal personality disorder showed a mild to moderate general reduction in performance on all measures. Verbal measures of persistence, short-term retention, and learning were more severely impaired than their nonverbal analogs. Performance on measures of memory retention was independent of modality.

CONCLUSIONS

The results are consistent with previous reports that have suggested a mild, general decrement in cognitive performance and proportionately greater involvement of the left hemisphere in patients with schizotypal personality disorder. The findings provide further support for a specific deficit in the early processing stages of verbal learning.

Schizophrenia: genes and environment

The historical and genetic foundations of our current understanding of schizophrenia are reviewed, as are the present and future directions for research. Genetic epidemiological investigations, including family, twin, and adoption studies have confirmed the contributions of genetic and environmental determinants of schizophrenia. For example, identical twins show average concordance rates of only 50%; rates of 100% would be expected on the basis of genetic equivalence alone. Genetic factors may cause errors in brain development and synaptic connections. A broad range of environmental components may further damage the brain. Biological components may include pregnancy and delivery complications, such as intrauterine fetal hypoxia, infections, and malnutrition. Primarily nonbiological components may include psychosocial stressors, such as residence in an urban area and dysfunctional family communication. It is likely that the environmental factors interact with the genetic liability in a negative manner to produce disorders in the schizophrenic spectrum. Genetic and environmental components of the disorder are examined, as well as their interactions in producing either neurodevelopmental syndromes or schizophrenia itself. The implication of these findings for prevention and treatment are considered.

Spatial working memory: absence of gender differences in schizophrenia patients and healthy control subjects

BACKGROUND

Spatial working memory dysfunction has been suggested to be a cardinal feature of schizophrenia. But schizophrenia is heterogeneous in its clinical profile, course, and outcome. One fundamental contributor to this heterogeneity may be gender. No report has yet addressed gender differences in spatial working memory, as measured by the delayed-response task (DRT).

METHODS

We aggregated data from three previously published studies of spatial working memory in schizophrenia and also collected DRT data from a new sample of subjects in order to examine potential gender differences in DRT performance.

RESULTS

As previously reported, schizophrenia patients (n = 71) showed deficits in spatial working memory relative to normal control subjects (n = 213), however, no within-group or between-group gender differences were present.

CONCLUSIONS

These findings provide evidence for the absence of gender differences in spatial working memory function.

Gonadal steroids in the treatment of mood disorders

Increased interest in the complex interplay between gonadal steroids and neurotransmitter systems involved in mood has led investigators to question the role of gonadal steroids in the treatment of affective disorders, especially in women.

OBJECTIVES

The purpose of this article is to provide a rationale for using gonadal hormones in the treatment of depression in women.

METHODS

The literature is reviewed regarding 1) sex-specific phenomenologic and epidemiologic differences in the manifestation of psychiatric illness, 2) sex-specific differences in the therapeutic and adverse effects of psychotropic medications, 3) the complex interplay between gonadal steroids and neurotransmitter systems implicated in psychiatric disorders, and 4) the growing literature regarding the use of estrogen and progesterone in the treatment of mood disorders in women and androgens in the treatment of depression and sexual dysfunction in both men and women.

RESULTS

Findings from pharmacologic trials of estrogen and androgens are encouraging, albeit mixed, in the treatment of mood disorders and decreased libido in women, respectively. Controlled studies have failed to confirm early open-label reports of the effectiveness of progesterone in the treatment of premenstrual syndrome.

CONCLUSIONS

Pending replication, estrogen may become an important pharmacologic agent in the treatment of postnatal and perimenopausal depression, whereas androgens have been shown to improve libido in postmenopausal women and hypogonadal men. Progesterone cannot be recommended as a treatment for premenstrual syndrome or postnatal depression.