General Population Birth Cohort Research Articles

Evidence for similar developmental precursors of chronic affective illness and schizophrenia in a general population birth cohort

The capacity of 17 functions to represent the size distribution of fragmented rock is assessed on 1234 data sets of screened fragments from blasted and crushed rock of different origins, of sizes ranging from 0.002 to 2000 mm. The functions evaluated are Weibull, Grady, log-normal, log-logistic and Gilvarry, in their plain, re-scaled and bi-component forms, and also the Swebrec distribution and its bi-component extension. In terms of determination coefficient, the Weibull is the best two-parameter function for describing rock fragments, with a median R2 of 0.9886. Among re-scaled, three-parameter distributions, Swebrec and Weibull lead with median R2 values of 0.9976 and 0.9975, respectively. Weibull and Swebrec distributions tie again as best bi-component, with median R2 of 0.9993. Re-scaling generally reduces the unexplained variance by a factor of about four with respect to the plain function; bi-components further reduce this unexplained variance by a factor of about two to three. Size-prediction errors are calculated in four zones: coarse, central, fines and very fines. Expected and maximum errors in the different ranges are discussed. The extended Swebrec is the best fitting function across the whole passing range for most types of data. Bimodal Weibull and Grady distributions follow, except for the coarse range, where re-scaled forms are preferable. Considering the extra difficulty in fitting a five-parameter function with respect to a three-parameter one, re-scaled functions are the best choice if data do not extend far below 20% passing. If the focus is on the fine range, some re-scaled distributions may still do (Weibull, Swebrec and Grady, with maximum errors of 15–20% at 8% passing), but serious consideration should be given to bi-component distributions, especially extended Swebrec, bimodal Weibull and bimodal Grady.

Evidence for similar developmental precursors of chronic affective illness and schizophrenia in a general population birth cohort

Evidence for similar developmental precursors of chronic affective illness and schizophrenia in a general population birth cohort

Poor scholastic achievement and premorbid social decline in schizophrenia

An increased rate of non-righthandedness and other abnormalities of lateralization have been reported in schizophrenia. We investigated childhood hand preference and eye dominance as risk factors for adult schizophrenia among a general population birth cohort. Pre-schizophrenic children showed a significant excess of left-eye dominance at age 11 when compared with controls (OR 2.5, 1.0–5.8, p=0.03), but there was no significant difference in hand preference between pre-schizophrenic children and controls.