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Biomedical subjects

G Thaker

Publications and source records attributed to G Thaker.

17 recordsLinked to original sources
PubMed2001

Genetic epidemiology and schizophrenia: a study of reproductive fitness.

Genetic epidemiological studies have demonstrated markedly reduced rates in reproduction among schizophrenic patients. According to evolutionary theory, behavioral and psychological phenotypes are selected based on ecological "fit". Where differential survival or reproductive success exists, genotype frequencies are altered in subsequent generations. In the case of schizophrenia, lower rates of reproduction constitute a negative selection factor that should reduce genes in the population associated with the expression of the disease--ultimately leading to decreases in prevalence. However, studies reveal a stable prevalence of about 1% over time. Attempts to explain the apparent contradiction between negative selection and stable prevalence have taken several forms. One explanation suggests that reproductive rates in relatives of schizophrenic patients are increased--compensating for reproductive loss in affected family members. Family data from schizophrenic patients at the Maryland Psychiatric Research Center were compared with those of healthy volunteers and volunteers with schizophrenia spectrum personality (SSP) disorders. Controlling for important socio-cultural and demographic variables, a multiple regression model revealed a significant increase in the number of siblings associated with schizophrenia. No differences in reproductive fitness were found among normal and SSP volunteers. This observed pattern in reproductive fitness provides one mechanism by which prevalence rates can remain stable despite lower reproductive rates among individuals with schizophrenia. Evidence of increased reproductive fitness in relatives suggests the need to consider the complex interactions of proximate and ultimate (evolutionary) mechanisms in the expression of schizophrenia.

Adult↗
PubMed2001

Smooth pursuit eye-tracking impairment in childhood-onset psychotic disorders.

OBJECTIVE: Although childhood-onset schizophrenia is relatively rare, a sizable group of children with severe emotional disturbances have transient psychotic symptoms that fall outside of current syndrome boundaries. The relationship of this group of children to those with childhood-onset schizophrenia and other childhood psychiatric disorders is unclear. In this study, the authors compared smooth pursuit eye tracking, a biological trait marker associated with schizophrenia, of children and adolescents with psychotic disorder not otherwise specified to that of children with childhood-onset schizophrenia and healthy comparison subjects. METHOD: By means of infrared oculography, smooth pursuit eye movements during a 17 degrees /second visual pursuit task were quantitatively and qualitatively compared in 55 young adolescents (29 with childhood-onset schizophrenia and 26 with psychotic disorder not otherwise specified) and their respective independent healthy comparison groups (a total of 38 healthy subjects). RESULTS: Subjects with childhood-onset schizophrenia had qualitatively poorer eye tracking, higher root mean square error, lower gain, and a greater frequency of catch-up saccades than healthy children. Subjects with psychotic disorder not otherwise specified also had qualitatively poorer eye tracking, higher root mean square error, and lower gain than healthy children, but saccade frequency did not differ significantly. CONCLUSIONS: Children with childhood-onset schizophrenia exhibit a pattern of eye-tracking dysfunction similar to that reported for adult patients. Similar abnormalities were seen in the subjects with psychotic disorder not otherwise specified except that they did not exhibit a greater frequency of catch-up saccades. Prospective longitudinal neurobiological and clinical follow-up studies of both groups are currently underway to further validate the distinction between these two disorders. Also, family studies are planned to establish whether eye-tracking dysfunction represents a trait- or state-related phenomenon in subjects with psychotic disorder not otherwise specified.

Adolescent↗
PubMed2001

Functional deterioration in individuals with schizophrenia spectrum personality symptoms.

Although previous studies have noted functional deterioration in patients with severe schizotypal symptoms who meet criteria for schizotypal personality disorder, we are not aware of any study which examines level of functioning in nonpatients who experience mild schizophrenia spectrum personality (SSP) symptoms. With this issue in mind, occupational functioning was examined in non-patient subjects with mild SSP symptoms. Patients were recruited from the community by newspaper advertisements or from the first-degree relatives of patients with schizophrenia. Individuals with no DSM-IIIR Axis I diagnosis and with SSP symptoms (n = 60) and without symptoms (n = 75) participated in the study. The two groups had similar mean age and years of education. Occupational function was evaluated using the Level of Function Scale. The SSP patients with mild symptoms had significantly lower occupational scores (5.62 + 2.50) than the non-SSP patients (7.76 + 0.69; p < 0.001). A total of 39% of SSP patients, compared with 3% of non-SSP patients showed poor occupational functioning (chi 2 = 31, df = 1, p < 0.001). There was a significant deterioration in the socioeconomic status in SSP patients compared with their parents' status. Patients with mild SSP symptoms who were otherwise healthy showed severe difficulties with occupational function. Further research is needed to identify subtle deficits underlying functional deterioration and to develop targets for treatment strategies.

Adult↗
PubMed1999

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Databases, Factual↗
PubMed1998

Recruitment of non-patient volunteers with schizophrenia spectrum personality symptoms.

Authors aimed to evaluate the yield and effectiveness of recruiting community schizophrenia spectrum personality (SSP) subjects via targeted newspaper advertisements listing SSP traits. Eight newspaper advertisements listing SSP traits were placed in regional newspapers over a 3-year period. Respondents (n = 209) were screened thoroughly via telephone, and eligible subjects were invited for face-to-face clinical interviews. One hundred and one subjects (48% of the respondents) were screened out over the phone and another 30% were no-shows or refused. Of the 46 subjects who were interviewed, a majority (24 subjects; 52%) met this study's criteria for SSP. These subjects experienced significant psychotic-like symptoms, as ascertained by a self-rating scale, and showed a downward drift in their socio-economic status. One can successfully recruit SSP subjects, with high yield, using targeted telephone advertisements combined with thorough telephone screening.

Adult↗
PubMed1997

Visual information-processing impairments in deficit and nondeficit schizophrenia.

OBJECTIVE: Previous studies of covert visuospatial attention in schizophrenia suggest a subtle form of right hemispatial neglect in acutely ill patients but not in chronic, stable patients. Because of previous work documenting various visual information-processing abnormalities in deficit schizophrenia, the authors investigated whether the deficit/nondeficit categorization would help clarify the presence of visual attentional asymmetries in schizophrenia. METHOD: Performance on a covert visuospatial attention task was examined in clinically stable outpatients with schizophrenia (17 in a deficit subgroup and 28 in a nondeficit subgroup) and 25 normal subjects. Peripheral cue and central cue versions of the covert visuospatial attention task, at 100-, 200-, and 800-msec intervals between cue and target, were administered a week apart. RESULTS: The nondeficit patients exhibited a significant and abnormal asymmetry, with slower reaction time to targets presented in the right visual field than in the left visual field. This right visual field disadvantage was found with both versions of the task, but only at the 100-msec cue-target interval. The deficit patients were slowest in overall reaction time but, similar to the normal subjects, showed no asymmetry. CONCLUSIONS: The results are consistent with slower visual information processing in the left compared to the right cerebral hemisphere in nondeficit schizophrenia. This finding cannot be accounted for by differences between the deficit and nondeficit subgroups in demographic characteristics, chronicity, or medication effects, nor is it secondary to generalized cognitive impairment.

Adolescent↗
PubMed1993

Psychosis proneness scales in schizophrenia spectrum personality disorders: familial vs. nonfamilial samples.

The authors evaluated the extent of overlap between DSM-III-R schizophrenia spectrum personality diagnoses (SSPD) and the Psychosis Proneness Scales of Chapman and his associates. The subjects were recruited from the family members of schizophrenic patients ("familial" subjects; n = 45) and members of the community with negative family histories for schizophrenia ("nonfamilial" subjects; n = 60). Clinical interviews were performed to obtain DSM-III-R Axis I and II diagnoses. In 105 individuals with no Axis I diagnosis, the five Chapman Scales were administered. The results suggest that the nonfamilial subjects with diagnoses of SSPD (n = 24) scored significantly higher on the Chapman Scales of Magical Ideation, Perceptual Aberration, and Impulsive Nonconformity compared with the familial SSPD subjects and the other non-SSPD groups. The familial SSPD subjects (n = 17) scored significantly higher than the nonfamilial, non-SSPD groups on the Physical Anhedonia Scale. Scores on the Social Anhedonia Scale were highest in the SSPD subjects, but only scores for the nonfamilial SSPD subjects were statistically different from those for the other non-SSPD groups. The data were reanalyzed by first dividing the scores from the Chapman Scales into high and low scores based on different cutoff points. Sensitivities, specificities, and predictive powers of the "high" Chapman scores for SSPD diagnoses were then calculated. These were done because the Chapman Scales are often used to identify individuals with schizophrenia-related personality disorders on the basis of scores that exceed arbitrary cutoff points. The results suggest that the Chapman Scales (other than the Physical Anhedonia Scale) and DSM-III-R criteria identified mostly the same subjects, when only nonfamilial subjects were considered (with sensitivities and specificities of about 0.70). However, the overlap between these two constructs was poor when only schizophrenia spectrum subjects recruited from the family members of schizophrenic patients were considered.

Adult↗
PubMed1993

Changes in psychopathology and dyskinesia after neuroleptic withdrawal in a double-blind design.

The goal of this study was to assess the time course of change in psychopathology and dyskinesia after neuroleptic withdrawal. Fifteen DSM-III schizophrenic patients were abruptly withdrawn in a double-blind fashion from stable haloperidol treatment. Weekly ratings of dyskinesia and psychopathology were performed for 4 weeks post-withdrawal. There was an overall increase in dyskinesia ratings over the 4-week period (p < 0.05) beginning in week 2, with dyskinetic movements of the fingers showing the most significant increase (p < 0.001). There were no overall changes in psychopathology, though the group appeared to be bimodal with 6 of the 15 patients showing a significant relapse in psychotic symptoms. Neither baseline TD nor psychotic relapse significantly interacted with change in TD over time. These schizophrenic patients showed an increase in global dyskinesia rating early within four weeks of neuroleptic withdrawal. This time course did not appear to be associated with reemergence of psychopathology which occurred later. A significant minority of patients relapsed within this time period. This suggests the relative safety of brief periods of neuroleptic withdrawal for carefully selected patients in a controlled setting with specific goals (e.g., for evaluation or in preparation for clozapine) and the need to further understand who is at risk for rapid relapse.

Adolescent↗
PubMed1993

Psychiatric illnesses in families of subjects with schizophrenia-spectrum personality disorders: high morbidity risks for unspecified functional psychoses and schizophrenia.

OBJECTIVE: The authors determined morbidity risks for psychiatric illnesses in the families of probands with schizophrenia-spectrum personality disorders. METHOD: Subjects were recruited from the community through newspaper advertisements. Subjects were identified as having schizophrenia-spectrum personality disorders (N = 30) if they met at least three, four, or three DSM-III-R criteria for schizoid (N = 14), schizotypal (N = 20), and/or paranoid (N = 15) personality disorder, respectively. The comparison subjects had no psychiatric diagnoses (N = 8) or had other personality disorders (N = 12); none of the subjects in either group had any DSM-III-R axis I diagnosis. Trained interviewers collected family history information about the relatives of the two groups; the interviewers were blind to the probands' diagnoses. RESULTS: The risks for schizophrenia, other functional psychoses, and schizophrenia-spectrum personality disorders were significantly higher in the relatives of subjects with schizophrenia-spectrum personality disorders than in the families of the comparison subjects. CONCLUSIONS: The high rate of schizophrenia in the families of probands with schizophrenia-spectrum personality disorders is consistent with the previous findings of higher than normal rates of these personality disorders in the biological relatives of schizophrenic patients. The significance of the high rate of unspecified functional psychoses is unclear. Use of the family study method, by which valid differential diagnosis of psychoses is possible, is indicated. The results from the current study do not rule out the possibility that the schizophrenia-spectrum personality disorders are related to psychoses in general rather than specifically to schizophrenia.

Adult↗
PubMed1992

Abnormal electroretinography in schizophrenic patients with a history of sun gazing.

Electroretinographic (ERG) measurements were performed in 9 schizophrenic patients and in 13 control subjects. The measurements of schizophrenic patients as a group did not differ from those of normals. However, 6 schizophrenic patients who had a past history of sun gazing showed a decrease in retinal responsiveness under conditions of light adaptation. These results suggest that a subgroup of schizophrenic patients, who show deviant light-related behavior, have abnormal ERG. We postulate that an abnormality in retinal dopaminergic neurons, which are known to reduce light responsiveness of horizontal and ganglion cells, is the underlying pathophysiology of this clinical finding.

Adaptation, Ocular↗
PubMed1991

Photophilic and photophobic behaviour in patients with schizophrenia and depression.

The authors interviewed 32 patients (25 with an RDC diagnosis of schizophrenia and seven with schizoaffective disorder) consecutively admitted to a psychiatric outpatient clinic. Ten patients had a history of photophilic behaviour with sun-gazing, while 20 patients showed no unusual behaviour related to light. Two patients who had depressive symptoms at the time of interview had a history of photophobic behaviour. Sixteen patients and 12 controls were tested for their threshold for discomfort of high intensity light; the thresholds were significantly higher in the patients with schizophrenia (especially in those with history of sun gazing). The implications of these findings for clinical practice and research are discussed.

Adult↗
PubMed1989

Oculomotor abnormalities and their clinical correlates in schizophrenia.

Smooth pursuit eye movements (SPEMs) have been consistently found to be abnormal in the majority of schizophrenic patients. The traditional SPEM measurement technique, however, fails to inform us about the underlying oculomotor deficit in these patients, since it remains a non-specific and a global oculomotor measure. A number of diverse clinical features such as tardive dyskinesia (TD) or negative symptoms correlate with the SPEM abnormality. Other eye movement abnormalities such as fixation difficulties, increased "volitional" saccadic latency and saccadic distractibility in anti-saccade paradigm have also been noted in schizophrenic patients. Still, it remains unclear how these different eye movement measures relate with each other and with the traditional SPEM measure, the presence of which is so widely described in schizophrenia. The advantage of some newer oculomotor paradigms is their functional specificity and the degree to which their biology is known. To further address these issues and to search for clinical correlates of various eye movement abnormalities found in schizophrenia, we have developed a battery of oculomotor measures to be administered to a large number of clinically well described schizophrenic patients and normal controls. The results from a preliminary analysis of a relatively small number of subjects are presented here, thus limiting the scope of possible conclusions. But, these results do indicate that this technique of studying multiple paradigms for oculomotor control in schizophrenia may prove to be fruitful.

Eye Movements↗