Biomedical subjects

J Van Os

Publications and source records attributed to J Van Os.

At least 19 recordsLinked to original sources

PubMed2006

Is an Angoff standard an indication of minimal competence of examinees or of judges?

BACKGROUND: To establish credible, defensible and acceptable passing scores for written tests is a challenge for health profession educators. Angoff procedures are often used to establish pass/fail decisions for written and performance tests. In an Angoff procedure judges' expertise and professional skills are assumed to influence their ratings of the items during standard-setting. The purpose of this study was to investigate the impact of judges' item-related knowledge on their judgement of the difficulty of items, and second, to determine the stability of differences between judges. METHOD: Thirteen judges were presented with two sets of 60 items on different occasions. They were asked to not only judge the difficulty of the items but also to answer them, without the benefit of the answer key. For each of the 120 items an Angoff estimate and an item score were obtained. The relationship between the Angoff estimate and the item score was examined by applying a regression analysis to the 60 items (Angoff estimate, score) for each judge at each occasion. RESULTS AND CONCLUSIONS: This study shows that in standard-setting the individual judgement of the individual item is not only a reflection of the difficulty of the item but also of the inherent stringency of the judge and his/her subject-related knowledge. Considerable variation between judges in their stringency was found, and Angoff estimates were significantly affected by a judge knowing or not knowing the answer to the item. These findings stress the importance of a careful selection process of the Angoff judges when making pass/fail decisions in health professions education. They imply that judges should be selected who are not only capable of conceptualising the 'minimally competent student', but who would also be capable of answering all the items.

Clinical Competence↗

PubMed2006

Evidence for instrument and family-specific variation of subclinical psychosis dimensions in the general population.

It is unknown to what degree dimensions of schizotypy (subclinical psychosis) show independent, family-specific variation in the general population. Psychologists administered the Community Assessment of Psychic Experiences, the Structured Interview for Schizotypy-Revised (SIS-R), and the Brief Psychiatric Rating Scale to 257 subjects pertaining to 82 general population families. All 3 instruments showed family-specific variation for positive and negative subclinical psychosis dimensions with between-families proportions of total variance between 10% and 40%. However, only the SIS-R showed family-specific variation of the negative dimension independent of its correlation with the positive dimension. The positive dimension of subclinical psychosis shows familial-specific variation in samples unselected for psychiatric disorder, suggesting dimensional liability in the population. The SIS-R additionally captures family-specific variation in the negative domain.

Adult↗

PubMed2006

Prediction of change in level of problem behavior among children of bipolar parents.

OBJECTIVE: To determine the effects of familial loading, birth weight, and family problems on change in parent-reported problems across a 14-month period among children of bipolar parents. METHOD: Emotional and behavioral problems in a sample of 140 offspring of bipolar parents and familial loading in first- and second-degree relatives were assessed at two measurements. Parents reported the birth weight of their offspring and completed a questionnaire on family problems. Multiple linear regression analyses were performed to assess associations of the three predictors with change in problem scores at follow-up. RESULTS: Familial loading of unipolar disorder was a unique predictor for an increase in problem scores from the first to the second measurement with beta-coefficients ranging from 0.17 to 0.25. Birth weight and family problems were not associated with change in problem scores across the two measurements. CONCLUSION: Familial loading of unipolar disorder predicted an increase in behavioral and emotional problems across the 14-month follow-up.

Adolescent↗

PubMed2005

Incidence and distribution of first-episode mania by age: results from a 35-year study.

BACKGROUND: Few epidemiological studies have investigated incidence by age or age at onset distributions for mania or bipolar disorder. The current study aimed to determine these in a defined area in south-east London, over a 35-year period. METHOD: All cases of first-episode mania presenting to psychiatric services in Camberwell, south-east London, between 1965 and 1999 were identified. Incidence rates by age, using 5-year age-at-onset bands, were estimated and the structure of the age-at-onset distribution for first-episode mania was investigated using finite mixture distributions (admixture analysis). RESULTS: The incidence of DSM-IV bipolar I disorder (BP I), first manic episode peaked in early adult life (16.38/100,000 population per year in the 21-25 years band) with a much smaller peak in mid-life. A two-component normal mixture distribution fitted age at onset better than either a single normal distribution or a three-component mixture, implying the existence of early and later onset subgroups. The early onset group had a stronger family history of bipolar disorder, and showed more acute, severe and atypical symptoms during their first manic episode. CONCLUSIONS: The incidence of mania peaks in early adult life but there is clear evidence of early and later onset subgroups which may represent different forms of disorder.

Adult↗

PubMed2004

Is our concept of schizophrenia influenced by Berkson's bias?

BACKGROUND: If both positive and negative dimensions of schizophrenia independently influence need for care, a higher estimate of the comorbidity between these dimensions is expected in clinical samples than would be the case if non-clinical cases were investigated (i.e. Berkson's bias). The present paper investigates whether positive and negative dimensions independently contribute to mental health care use in a general population sample. METHOD: A prospective cohort study was conducted, in which 7076 individuals were interviewed with the Composite International Diagnostic Interview Schedule at baseline and 1 and 3 years later. Lifetime positive and negative psychotic experiences (PPE, NPE) were assessed at baseline. Mental health care use (MHC) was assessed at baseline, and prospectively 1 and 3 years later. RESULTS: The rating of MHC was strongly associated with NPE and PPE, both retrospectively and prospectively and the effects of both variables remained strong and significant in the analyses with both variables included. CONCLUSIONS: These results, therefore, suggest that the concept of schizophrenia, as a unitary entity with high comorbidity between positive and negative dimensions, is in part the result of Berkson's bias.

Adolescent↗

PubMed2004

Abnormal response to metabolic stress in schizophrenia: marker of vulnerability or acquired sensitization?

BACKGROUND: Previous work suggests that individuals with schizophrenia display an altered homovanillic acid (HVA) response to metabolic stress. The present study replicated and extended this paradigm, including individuals with elevated genetic risk for schizophrenia. METHOD: Patients with psychosis (n = 50), non-psychotic first-degree relatives of patients with psychosis (n = 51) and controls without psychosis (n = 50) underwent, in randomized order, double-blind administration of placebo and the glucose analogue 2-deoxy-D-glucose (2DG), which induces a mild, transient clinical state of glucoprivation. Plasma HVA and cortisol were assessed twice before the start of the 2DG/placebo infusion (baseline values), as well as four times post infusion. Data were analysed using multi-level random regression techniques. RESULTS: During the stress condition, significant increases in plasma HVA and cortisol were found. The increase in plasma HVA level during the stress condition was significantly stronger in patients than in controls, whereas this was not the case in relatives v. controls. The increase in plasma cortisol during the stress condition was significantly less in patients than controls, but no significant difference in the increase of plasma cortisol during stress was found in the comparison between relatives and controls. CONCLUSIONS: Patients with psychosis, but not their non-psychotic first-degree relatives, show an altered neurobiological response to metabolic stress, suggesting that this dysregulation is not a genetically transmitted vulnerability, but an illness-related effect, possibly reflecting acquired sensitization of neuroendocrine systems by repeated environmental stressors or repeated stimulation with agonistic drugs.

Adolescent↗

PubMed2004

Dimensions of depression, mania and psychosis in the general population.

BACKGROUND: In order to investigate whether correlated but separable symptom dimensions that have been identified in clinical samples also have a distribution in the general population, the underlying structure of symptoms of depression, mania and psychosis was studied in a general population sample of 7072 individuals. METHOD: Data were obtained from the three measurements of the Netherlands Mental Health Survey and Incidence Study (NEMESIS). Symptoms of depression, mania and the positive symptoms of psychosis were assessed using the Composite International Diagnostic Interview. Confirmatory factor-analysis was used to test statistically the fit of hypothesized models of one, two, three or seven dimensions. RESULTS: The seven-dimensional model comprising core depression, sleep problems, suicidal thoughts, mania, paranoid delusions, first-rank delusions and hallucinations fitted the data best, whereas the unidimensional model obtained the poorest fit. This pattern of results could be replicated at both follow-up measurements. The results were similar for the subsamples with and without a lifetime DSM-III-R diagnosis. The seven dimensions were moderately to strongly correlated, with correlations ranging from 0.18 to 0.73 (mean 0.45). CONCLUSIONS: In the general population, seven correlated but separable dimensions of experiences exist that resemble dimensions of psychopathology seen in clinical samples with severe mental illness. The substantial correlations between these dimensions in clinical and non-clinical samples may suggest that there is aetiological overlap between the different dimensions regardless of level of severity and diagnosable disorder.

Adolescent↗

PubMed2004

Early adolescent cannabis exposure and positive and negative dimensions of psychosis.

AIMS: To investigate the effect of exposure to cannabis early in adolescence on subclinical positive and negative symptoms of psychosis. DESIGN: Cross-sectional survey in the context of an ongoing cohort study. SETTING: Government-supported general population cohort study. PARTICIPANTS: A total of 3500 representative 19-year olds in Greece. MEASUREMENTS: Subjects filled in the 40-item Community Assessment of Psychic Experiences, measuring subclinical positive (paranoia, hallucinations, grandiosity, first-rank symptoms) and negative psychosis dimensions and depression. Drug use was also reported on. FINDINGS: Use of cannabis was associated positively with both positive and negative dimensions of psychosis, independent of each other, and of depression. An association between cannabis and depression disappeared after adjustment for the negative psychosis dimensions. First use of cannabis below age 16 years was associated with a much stronger effect than first use after age 15 years, independent of life-time frequency of use. The association between cannabis and psychosis was not influenced by the distress associated with the experiences, indicating that self-medication may be an unlikely explanation for the entire association between cannabis and psychosis. CONCLUSIONS: These results add credence to the hypothesis that cannabis contributes to the population level of expression of psychosis. In particular, exposure early in adolescence may increase the risk for the subclinical positive and negative dimensions of psychosis, but not for depression.

Adolescent↗

PubMed2003

Do life events have their effect on psychosis by influencing the emotional reactivity to daily life stress?

BACKGROUND: Life events (LE) have consistently been found to influence course and outcome of psychotic disorders. However, the mechanism through which they operate is not known. The present study investigated whether LE have their effect by impacting on the emotional sensitivity for daily hassles. METHOD: Patients with clinically remitted psychotic illness (N=42) were studied with the Experience Sampling Method (a structured diary technique assessing current context and mood in daily life) to assess: (1) appraised subjective stress related to daily events and activities; and (2) emotional reactivity conceptualized as changes in both negative affect (NA) and positive affect (PA). LE were assessed with the Brown & Harris Life Event and Difficulties Schedule. RESULTS: Multilevel regression analyses showed that previous exposure to LE influenced the appraised stressfulness of neither daily events nor the activities in which the subjects were involved. However, a history of LE did modify the emotional reaction to daily life stress, both in models predicting NA and in models predicting PA. CONCLUSIONS: By their cumulative effect on emotional reactivity to daily activities and events, LE may render individuals more vulnerable to the onset or persistence of psychotic experiences.

Adult↗

PubMed2003

Emotional reactivity to daily life stress in psychosis and affective disorder: an experience sampling study.

OBJECTIVE: To investigate the emotional reactivity to small disturbances in daily life in patients with non-affective psychosis (NAP), bipolar disorder (BD) and major depression [major depressive disorder (MDD)]. METHOD: Forty-two patients with NAP, 38 with BD, 46 with MDD, and 49 healthy controls were studied with the experience sampling method to assess (i) appraised subjective stress of small disturbances in daily life and (ii) emotional reactivity, reflected in changes in positive affect (PA) and negative affect (NA). RESULTS: Multilevel regression analyses showed an increase in NA in MDD, a decrease in PA in BD and both an increase in NA and a decrease in PA in NAP in association with the subjectively stressful situations, compared with the control subjects. CONCLUSION: Individuals with NAP, MDD and BD display differences in emotional stress reactivity. Type of mood disorder may exert a pathoplastic effect on emotional reactivity in individuals with MDD and BD. Individuals with NAP may be most vulnerable to the effects of daily life stress.

Activities of Daily Living↗

PubMed2003

Incidence of schizophrenia in south-east London between 1965 and 1997.

BACKGROUND: There has been much debate about changes in the incidence of schizophrenia. AIMS: To identify any changes in incidence of schizophrenia in Camberwell, south-east London, between 1965 and 1997. METHOD: Research Diagnostic Criteria and DSM-III-R diagnoses were generated for all first contacts by the OPCRIT computer program, and incidence rates of schizophrenia in seven time periods were measured. Indirect standardisation and Poisson models were used to measure the effect of time period and to examine interactions with age and gender. RESULTS: There was a continuous and statistically significant increase in the incidence of schizophrenia, which was greatest in people under 35 years of age and was not gender-specific. CONCLUSIONS: The incidence of schizophrenia has doubled in south-east London over the past three decades.

Adult↗

PubMed2002

Evidence that three dimensions of psychosis have a distribution in the general population.

BACKGROUND: The aims of the study were: first to examine, using clinical symptoms of patients as a template, whether the correlated but independent dimensions of positive, negative and depressive symptoms that have been identified in clinical psychosis, also have a distribution as non-clinical experiences in the general population; and second, to establish to what degree population variation in experience of positive and negative features of psychosis is actually independent of experience of depression. METHOD: In a representative population sample of 932 young men, we measured experiences of positive, negative and depressive features of psychosis, using a 40-item self-report instrument. Confirmatory factor analysis was used to compare the fit of hypothesized one-, two- and three-factor solutions. RESULTS: A three-factor model of separate depressive, positive and negative dimensions provided a better fit to the data than either a two-factor or unidimensional model. All three dimensions were correlated with each other, but also showed good discriminant validity in relation to established scales, confirming their relative independence. CONCLUSION: The data suggest that the correlated dimensions of clinical psychosis also have a distribution in the general population, and that depressive symptoms may form an integral part of psychosis-like experiences in the general population.

Adolescent↗

PubMed2002

Prenatal life and post-natal psychopathology: evidence for negative gene-birth weight interaction.

BACKGROUND: Many studies suggest that pregnancy and birth complications (PBCs) are environmental risk factors for child psychopathology. However, it is not known whether the effects of PBCs occur independently of genetic predisposition. The current study examined the possibility of gene-environment interaction in a twin design. METHOD: The East Flanders Prospective Twin Survey prospectively records the births of all twin pairs born in East Flanders, Belgium. The current study included 760 twin pairs aged 6-17 years. Multilevel regression analysis was used to assess the effects of several PBCs collected around the time of birth. Using structural equation modelling, ACE models assuming additive genetic (A), shared environmental (C) and unique environmental (E) influences, were compared in order to examine whether the contribution of genetic factors to parent-rated child problem behaviour varied as a function of exposure to dichotomously and continuously defined PBCs. RESULTS: A main independent effect of lower birth weight, corrected for gestational age (small for gestational age--SGA), on child problem behaviour was found. In addition, there was an interaction between genetic influence and SGA, in that being smaller for gestational age resulted in less influence of additive genetic factors on individual differences in problem behaviour. CONCLUSIONS: Results are suggestive of negative gene-birth weight interaction. Children who are SGA are less sensitive to the genetic effects, and those with high genetic vulnerability are less sensitive to the effects of being SGA in bringing about post-natal mental health effects.

Adolescent↗

PubMed2001

Neuroticism as a risk factor for schizophrenia.

BACKGROUND: Neuroticism has been shown to increase the risk of depression whereas extraversion is associated with a reduction of risk. These personality traits play a central role in aetiological theories of affective disorder but their role in schizophrenia is unclear. In this study, the risk for schizophrenia associated with neuroticism and extraversion was examined and quantified. METHODS: Neuroticism and extraversion rated at the age of 16 years were examined in relation to adult schizophrenia in a national birth cohort of 5362 individuals. RESULTS: Neuroticism increased the risk of later schizophrenia independent of the level of affective symptoms in adult life (odds ratio over three levels: 1.93, 95% CI 1.09-3.43), whereas extraversion reduced the risk (OR: 044, 95% CI 0.23-0.84). CONCLUSIONS: Depression and schizophrenia may share personality risk-increasing and risk-reducing factors. Coping styles associated with particular personality traits may determine whether isolated symptoms progress to full-blown illness.

Adaptation, Psychological↗

PubMed2001

Comparison of the outcome and treatment of psychosis in people of Caribbean origin living in the UK and British Whites. Report from the UK700 trial.

BACKGROUND: The comparative outcome of psychosis in British Whites and UK African-Caribbeans is unclear. Some report that African-Caribbeans have worse outcome, whereas others claim better symptomatic outcome and a more benign course. AIMS: To compare the course, outcome and treatment of psychosis in African-Caribbeans and British Whites in a large multi-centre sample. METHOD: A secondary analysis of 708 patients with research diagnostic criteria-defined psychosis from a 2-year, randomised controlled trial of case management. Outcome measures (hospitalisation, illness course, self-harm, social disability and treatment received) were adjusted for socio-economic and clinical differences between groups at baseline using regression analysis. RESULTS: African-Caribbeans were less likely to have a continuous illness and to receive treatment with antidepressant or psychotherapy. CONCLUSIONS: The outcome of psychosis is complex but differs between UK African-Caribbeans and British Whites. This may reflect risk factors that increase the rate of psychosis in UK African-Caribbeans. Treatment differences require further investigation.

Adolescent↗

PubMed2001

Comparison of the incidence of schizophrenia in rural Dumfries and Galloway and urban Camberwell.

BACKGROUND: Being born or living in urban areas is associated with high rates of schizophrenia. However, few studies have compared the incidence in urban/rural areas using the same methodology. AIMS: To compare service-based incidence rates for schizophrenia in rural Dumfries and Galloway in south-west Scotland with urban Camberwell in south-east London. METHOD: Using Research Diagnostic Criteria diagnoses from the OPCRIT computer algorithm, we compared the incidence of schizophrenia over 12 years (1979-1984 and 1992-1997) using indirect standardisation techniques and Poisson regression modelling. RESULTS: The incidence was 61% higher in urban Camberwell than in rural Dumfries and Galloway (standardised incidence ratio (SIR)=1.61; 95% CI=1.42-1.81). There was no difference in incidence when we compared the White population in Camberwell with Dumfries and Galloway (SIR=1.12; 95% CI=0.86-1.43). CONCLUSIONS: The incidence of schizophrenia in urban Camberwell was higher than that in rural Dumfries and Galloway; the high incidence of non-Whites in Camberwell largely explains the urban/rural difference.

Adolescent↗

PubMed2000

Increased morbid risk for schizophrenia in families of in-patients with bipolar illness.

BACKGROUND: It has been reported that relatives of probands with severe, psychotic forms of bipolar illness have increased rates of schizophrenia but not the relatives of individuals with milder, non-psychotic forms of disorder. In this study, we examined the prevalence of psychiatric disorders in the first degree relatives of a sample of 103 inpatients with bipolar disorder and in a matched control sample of 84 healthy individuals. METHOD: Relatives of cases and controls were interviewed using the FH-RDC to determine familial morbid risk for schizophrenia and bipolar disorder. Age- and sex-adjusted morbidity risks were calculated in both samples according to the method of Strömgren. RESULTS: The morbid risks for both bipolar disorder (4.9%) and schizophrenia (2.8%) were higher in relatives of patients than in relatives of controls (0.3% and 0.6% respectively). The relative risks were 14.2 [95% confidence interval (CI)=3.1-64.2] for bipolar disorder and 4.9 (95% CI=1.3-18.8) for schizophrenia. Relatives of women with early onset of bipolar illness had the highest morbid risks for both bipolar illness and schizophrenia. The presence of more than one patient with bipolar disorder in a family increased the risk for schizophrenia nearly fourfold (RR=3.5, 95% CI=1.2-10.2). There was no additional effect of presence of psychotic features. CONCLUSION: Our results suggest that the transmission of psychosis is not disorder-specific. Bipolar illness characterised by a high familial loading is associated with increased risk of schizophrenia in the relatives.

Adolescent↗

PubMed2000

Schizophrenia is not disappearing in south-west Scotland.

BACKGROUND: Recent work has reported a decline in the incidence of schizophrenia, but it is unclear if these findings reflect a true decrease in its incidence or are an artefact arising from methodological difficulties. AIMS: To take account of these methodological difficulties and report service-based incidence rates for schizophrenia in Dumfries and Galloway in south-west Scotland for 1979-98. METHOD: Using both clinical diagnoses and diagnoses generated from the Operational Checklist for Psychotic Disorders (OPCRIT) computer algorithm for ICD-10 and DSM-IV schizophrenia, we measured change in the incidence rates over time. We used indirect standardisation techniques and Poisson models to measure the rate ratio linear trend. RESULTS: There was a monotonic and statistically significant decline in clinically diagnosed schizophrenia. The summary rate ratio linear trend was 0.77. However, using OPCRIT-generated ICD-10 and DSM-IV diagnoses, there was no significant difference over time. CONCLUSIONS: OPCRIT-generated consistent diagnoses revealed no significant fall in the incidence of schizophrenia. Changes in diagnostic practice have caused the declining rates of clinically diagnosed schizophrenia in Dumfries and Galloway.

Factor Analysis, Statistical↗