This paper reports the baseline neurocognitive results of a sample of 91 adult participants, age 16 to 30 (AR = 40, FE = 15, HC = 36). The younger adolescent participants (< age 16) were not included in the current analyses due to the small sample size and the administration of different tests (e.g., WISC-III subtests).
3.1. Program Participant Characteristics
Demographic and clinical characteristics of this sample are summarized in . The three groups (AR, FE, HC) were not significantly different in age, parental education, gender, handedness, or ethnicity. The AR and FE groups had similar family histories. The AR and FE groups presented with similar overall levels of global functioning (GAF) and clinical symptoms as measured by the BPRS and SANS. The FE sample had more positive psychotic symptoms, as assessed by the global SAPS, compared to the AR group (t
 = 3.32, p
<0.002). These sample characteristics support the developmental model that negative symptoms precede positive symptoms in the pathogenesis of psychotic disorders (Cornblatt et al., 2002
Demographic and clinical characteristics of the sample.
The AR and FE samples did not significantly differ in the number taking a psychotropic medication (21/40 AR versus 11/15 FE). Of the 21 AR participants receiving a psychotropic medication at baseline, 11 were receiving more than one. Significantly more FE participants (11/15) were receiving antipsychotic treatment at the time of their baseline evaluation compared to the AR participants (12/40); although average length of antipsychotic treatment was similar for both groups (FE: 18.1 weeks, AR: 17.6 weeks). All of those in the FE group were receiving atypical antipsychotic medications (risperidonel=7; olanzapine=3; ziprasidone=3). Several of the FE participants were receiving other medications (3 were also receiving an antidepressant, 2 were on an anticholinergic agent and 1 was receiving a benzodiazepine). Similarly, all twelve of the AR participants were receiving atypical antipsychotic medications (risperidone=7; olanzapine=3; quetiapine=1; aripiprizole=1). Additionally, there were nine AR participants receiving other psychotropic medications (antidepressants=8; benzodiapine=1). Post-hoc analyses revealed that although AR participants receiving an antipsychotic had more symptoms as indicated by Global SAPS, Global SANS, and Total SIPS (all NS) compared to the AR subjects not on an antipsychotic, a lower GAF score was the only measure that statistically differentiated the groups (F[1,39]=4.95, p<.05).
3.2 Neurocognitive Results
In this sample of 91 participants, there were nine who were missing one of the two measures from which one of the neurocognitive domain composite scores was derived. In each of these cases, their domain composite score was comprised of the one measure that was available. There were three participants who were missing both measures that comprised one domain composite score; for these cases, the score was imputed by averaging the remaining four domain composite scores, this average was then used for the missing domain composite score in the analysis as described in Twisk and de Vente (Twisk & de Vente, 2002
). Consequently, the following baseline results represent data from the whole sample of 91 participants (AR = 40, FE = 15, HC = 36).
There were significant group effects on the global neurocognitive performance index (F[2,91]=16.930, p<0.001) (see ). Follow-up Dunnett t-tests indicated that the AR and FE groups differed significantly from the HC sample (p<0.001). A Kruskal-Wallis test also showed a significant group effect (X2=31.93, p<0.001) and follow-up Mann-Whitney tests between AR and FE subjects versus HC were also significant (p<0.001).
Figure 1 Mean Global Neurocognitive Performance Index (SD) at baseline assessment across groups (F[2,91]=16.930, p<0.001). Post-hoc tests indicated that the at risk and first episode groups differed significantly from the healthy comparison sample (p<0.001). (more ...)
Significant group differences were present for each of the neurocognitive domains: 1) Processing Speed: F(2,91)=6.86, p<0.002, (Dunnett t-test AR vs HC: p<0.02; FE vs HC: p<0.002); 2) Working Memory: F(2,91)=12.24, p<0.001, (Dunnett t-test AR vs HC: p<0.001; FE vs HC: p<0.001); 3) Verbal Episodic Memory: F(2,91)=12.24, p<0.001, (Dunnett t-test AR vs HC: p<0.015; FE vs HC: p<0.001); 4) Executive Functioning: F(2,91)=6.69, p:<0.002, (Dunnett t-test AR vs HC: p<0.05; FE vs HC: p<0.002); and 5) Intellectual Functioning: F(2,91)=12.42, p<0.001, (Dunnett t-test AR vs HC: p<0.01; FE vs HC: p<0.01). Kruskal-Wallis and follow-up Mann-Whitney tests were also significant for the Executive Functioning (X2=13.52, p<0.001, AR vs HC: p<0.015, FE vs HC: p<0.001) and Intellectual Functioning (X2=18.40, p<0.001, AR vs HC: p<0.01, FE vs HC: p<0.001) domains. displays the group means across neurocognitive domains. displays the means of the individual test variables and univariate tests.
Figure 2 Means (SD) of neurocognitive domains from multivaritate analysis at baseline assessment. Significant group differences were present for each of the neurocognitive domains (p’s<0.002) and post hoc analyses showed significant group differences (more ...)
Analyses were unchanged when gender or parental education were added as a covariates into the analyses. Among the AR group, those who were taking antipsychotic medications (n=12) performed significantly worse, compared to the sample not taking antipsychotic medication, on the overall neurocognitive performance index (F [1,40]=6.14, p<.05), as well as the following individual cognitive domains: Attention (F[1,40]=4.58, p<.05); Working Memory (F[1,40]=5.69, p<.05); Executive Function (F[1,40]=5.60, p<.05); and Processing Speed (F[1,40]=7.09, p<.05).
3.3 Preliminary Analyses of Psychotic Conversion
Preliminary analyses that compare the baseline neurocognitive performance of participants who later converted to psychosis (true prodromals) to that of individuals who remained “at risk” at one year follow-up revealed that of the 30 AR participants who received one year follow-up, 5 (17%) had converted to psychosis (3 schizophrenia, 1 bipolar manic with psychosis, 1 psychosis NOS), while 25 (83%) remained at risk. Of the remaining 25 AR participants who received follow-up at one year, four no longer met criteria for an Axis I diagnosis, while the rest remained comorbid for a variety of diagnoses (7 mood disorder, 7 anxiety disorder, 4 mood + anxiety, 3 bipolar). We have previously reported on the demographic (older age, no family history of psychosis, more likely to be taking an antipsychotic), clinical symptom ratings (greater severity of ideas of reference, suspiciousness, disorganized thought) and other risk factors (history of substance abuse) that distinguished those who converted to psychosis at one year and those who had not (Haroun et al., 2006
). While it is recognized that the number of individuals who actually converted is small, and conclusions based on this small sample are premature, it is mentioned here because it replicates findings from previous studies (Brewer et al., 2005
; Lencz et al., 2006a
) and supports this general line of inquiry as well as the comparability of this sample to other studies of high-risk individuals.
As seen in , the true prodromal sample’s baseline performance on the neurocognitive performance index fell between the FE sample and the non-converted AR sample. The small number of true prodromals precludes meaningful parametric analyses of individual group differences, but the trend of group differences was evaluated using the nonparametric Jonckheere
Test for ordered alternatives (Jonckheere, 1954
), a between group trend test assessing the hypotheses that the median levels of neuropsychological performance decrease in an orderly fashion from HC to non-converted to true prodromals to FE. The Jonckheere
Test was highly significant, indicating the presence of a monotonic trend among the four groups (see , J* statistic = 5.63, p<0.00001).
Figure 3 Mean Global Neurocognitive Performance Index (SD) at baseline assessment. At risk subjects are divided into those who were “true prodromals”, who had converted to psychosis, and those who remained At Risk, because they had not experienced (more ...)
Although the true prodromals showed summary neuropsychological impairment that was intermediate in severity between impairment of the FE and AR groups, the pattern of the group performances on the individual ability areas is also of interest (see ). Relative to the HCs, the true prodromals evidence impairment that was of the same magnitude as that of the FE group on verbal episodic memory (Cohen d, effect size = 1.34 and 1.01 vs HCs respectively) (Cohen, 1988
) and general intelligence (effect size = 1.28 and 1.34 vs HCs respectively). The general intelligence impairment in the true prodromals and FE subjects appears to be accounted for primarily by the vocabulary subtest (effect size = 1.4 and 1.4 vs HCs respectively) rather than the block design subtest (effect size = .52 and .71 vs HCs respectively). On the other hand, the true prodromals showed comparable results to those of the AR group (and better than the FE group) on Processing Speed and Executive Functioning, and all of the three clinical groups showed approximately equal impairment relative to HCs on Working Memory (effect size range = 0.79 to 1.03).
Figure 4 Means (SD) of neurocognitive domains from the baseline assessment. At Risk subjects are divided into those who were “true prodromals”, who had converted to psychosis, and those who remained At Risk, because they had not experienced a psychotic (more ...)