EMERGENCE OF CHILDHOOD PSYCHIATRIC-DISORDERS - A MULTIVARIATE PROBIT ANALYSIS

We applied a computationally practical form of probit analysis for mul tiple response variables to data on early childhood development of fou r psychiatric disorders: disruptive disorders (DD - attention deficit disorders, oppositional defiant disorder, conduct disorder); adjustmen t disorders (ADJ); emotional disorders (ED - all anxiety disorders, de pression); and other DSM-III-R Axis I disorders (OTHER). In addition t o estimating the intercept slope and higher order polynomial terms for each age versus diagnosis regression, we estimated simultaneously the correlation among the four diagnostic categories. We then took into a ccount the correlation found among these four diagnostic categories wh en testing the hypothesis of no age effect, which would have been igno red in a piecemeal univariate approach. Regression lines for diagnosti c prevalence indicate a linear increase for OTHER disorders, and a cur vilinear increase for ED. We then used expected frequencies of individ ual response patterns (that is, the 2(4) = 16 possible diagnostic comb inations) in obtaining more precise estimates of diagnostic comorbidit y and its relation to age. We further generalize the Beck and Gibbons model to alternative specification of the random-effects distribution (that is, they assumed multivariate normality), illustrate how one can estimate the random-effects distribution empirically, and study the r obustness of parameter estimates to specification of the random-effect s distribution. (C) 1998 John Wiley & Sons, Ltd.