Posted by Phillipa on December 7, 2009, at 20:01:41
Study includes depression and bipolar also. Phillipa
From Medscape Medical News
Cognitive Impairments Shared by All Psychotic Disorders but Most Severe in Schizophrenia
Deborah Brauser
December 6, 2009 Cognitive deficits are found in all psychotic disorders but are most severe and pervasive in patients with schizophrenia and least pervasive in those with bipolar disorder or mania, according to results from a new study published online December 1 in the American Journal of Psychiatry.
The schizophrenia group presented widespread neuropsychological impairments and performed significantly worse than healthy comparison subjects on most neuropsychological measures, write Jolanta Zanelli, BSc, MSc, a PhD student in the Division of Psychological Medicine in the Institute of Psychiatry at King's College, London, England, and colleagues.
"Deficits in patients with bipolar disorder or mania were less pervasive but evident in performance scores on verbal memory and fluency tests," they add.
In an interview with Medscape Psychiatry, Ms. Zanelli said, "This is the first such study to compare all psychotic disorders: schizophrenia, bipolar disorder or mania, depressive psychosis, and other psychotic disorders, which include persistent delusional disorders, acute and transient psychotic disorders, other nonorganic psychotic disorders, and unspecified nonorganic psychosis."
"What was interesting to see was that cognitive impairment was seen across psychotic disorders and that the impairment was largely generalized," she added.
Comparisons May Have Important Implications
The study authors write that overwhelming evidence in the past has suggested that compromised neuropsychological function is frequently found in schizophrenia and is "typically characterized by prominent, specific deficits in memory and learning, executive functions, attention, and processing speed."
A comparison of the neuropsychological deficits in patients with schizophrenia with those who have other psychotic disorders "might have important implications for understanding the pathogenesis of these disorders and for nosological models of psychotic disorders," they speculate.
Past research has mainly focused on comparing schizophrenia with bipolar disorder or has used clinical rather than epidemiological samples, making the results difficult to generalize. In this study, the investigators sought to evaluate the neuropsychological performance of patients across all major diagnostic groups experiencing their first episode of psychosis.
"To our knowledge, this study represents the largest epidemiological cohort of first-episode psychosis patients with neuropsychological data," write the study authors.
"Many times, patients with psychiatric disorders complain about cognitive impairments," noted Ms. Zanelli. "Lots of research has been done on schizophrenia but not as much on other psychotic disorders. We hoped that this study would help us understand what is abnormal in brain function."
They examined data from the Aetiology and Ethnicity in Schizophrenia and Other Psychoses (AESOP) population-based study, which identified cases of first-episode psychosis in patients 16 to 65 years old who presented to mental health services in the United Kingdom between September 1997 and August 2000. A random sample of comparison subjects with no past or present psychotic disorder was also included.
Subjects included those diagnosed as having schizophrenia (n = 65), bipolar disorder or mania (n = 37), depressive psychosis (n = 39), or other psychotic disorders (n = 46) plus 177 healthy comparison samples.
All patients completed interview data, IQ measurements on the National Adult Reading Test, and a short form of the Wechsler Adult Intelligence Scale Revised neuropsychological test battery.
Schizophrenia Shows Worst Performance
The investigators found that the schizophrenia group exhibited widespread cognitive impairment and performed worse than the healthy comparison subjects on all 16 neuropsychological measures. In addition, 4 of these differences reached the Bonferroni-corrected level of significance (P ≤ .007).
Those with other psychotic disorders and with depressive psychosis also had widespread impairments compared with the healthy controls, with 6 and 8 measures reaching Bonferroni-corrected significance, respectively (P ≤ .007).
The bipolar disorder or mania group only performed significantly worse than the healthy controls on delayed verbal memory and category fluency (P ≤ .007).
When comparing the 4 diagnostic groups to each other, the bipolar disorder or mania group performed better on almost all neuropsychological measures. In addition, this group showed significantly better performance than the schizophrenia group on vocabulary and comprehension, digit symbol, letter-number span, and block design (P ≤ .007).
In an exploratory analysis of general intellectual ability, the results showed no statistically significant differences among the groups. However, when compared with the healthy control group:
The schizophrenia group showed significant impairment on the letter-number span test (P = .003);
The depressive psychosis group showed significant impairment on measures of verbal learning (P = .003) and category fluency (P = .004);
The psychotic disorders group showed significant impairment on verbal learning (P = .003); and
The bipolar or mania group showed significant impairment on category fluency (P = .003).
Generalized Cognitive Deficits
The main findings are that moderate to severe neuropsychological impairments characterize all psychotic disorders following the first psychotic episode and, by and large, the magnitude of impairment in specific neuropsychological functions reflects a generalized cognitive deficit," write the study authors.
"This was a very well-controlled study of the well-represented groups of patients," Ms. Zanelli added. "The finding that all psychotic disorders share cognitive impairments may suggest that they are as important as symptoms."
Limitations of the study include that patients were assessed soon after their first hospital admission (because diagnostic changes may occur over time), there was insufficient medication information, and no patients were drug naive. "Medication type and side effects can influence subjects' neuropsychological performance," write the study authors. "Nevertheless, we observed only weak correlations between neuropsychological functioning and symptom severity."
They add that future research with this cohort will focus on assessing the stability of the cognitive deficits across disorders, as well as the relationship of these deficits to clinical and functional outcome.
Such knowledge is likely to be valuable in designing early interventions for schizophrenia and other psychotic disorders, the authors conclude.
This study was funded by the United Kingdom Medical Research Council. The study authors have disclosed several financial relationships. The full list of disclosures can be found in the original article.
Am J Psychiatry. Published online December 1, 2009.
poster:Phillipa
thread:928476
URL: http://www.dr-bob.org/babble/20091206/msgs/928476.html