Aspects of cognitive function and schizotypy have been proposed as potential endophenotypes for schizophrenia. It is unknown if the expression of these endophenotypes at the population level is modulated by the genetic variability of candidate susceptibility genes for schizophrenia.

We examined the potential impact of 19 single nucleotide polymorphisms (SNPs) within five susceptibility genes for schizophrenia (COMT, DTNP1, NRG1, DAOA/G32 and DAAO genes) on cognition and self-rated schizotypy, in a representative population of 2,243 young male military conscripts. Single SNP and haplotype associations were evaluated.

Val carriers of the COMT val 158 met polymorphism, were associated with higher scores on the negative schizotypy factor, and a greater variability of response in attention capacity. DTNP1 SNPs rs2619522 and rs760761 exhibited several single marker associations, the minor alleles being associated with lower attention capacity but also a decrease in positive and paranoid schizotypy scores. DTNP1 haplotype load had borderline associations with non verbal IQ, paranoid schizotypy and sustained attention. For individual NRG1 polymorphisms, isolated but weak signals of association were noted with sustained attention and working memory, but not schizotypy. The risk allele of functional SNP8NRG243177 was associated with reduced spatial working memory capacity. An isolated effect of DAAO haplotype variability was noted on negative and disorganization schizotypy. No convincing association of DAOA/G32 variability was detected.

DTNP1 and val 158 met COMT, and less so NRG1 and DAAO variants, may exert gene-specific modulating effects on schizophrenia endophenotypes at the population level.

In this work we consider Cloninger's psychobiological model, which measures two dimensions of personality: character and temperament. Temperament refers to the biological basis of personality and its characteristics, while character refers to an individual's attitudes towards own self, towards humanity and as part of the universe.

The Temperament and Character Inventory-Revised-140 (TCI-R-140) was administered to 3 divergent samples: a general population sample, a sample of male conscripts and a sample of individuals attending a substance abuse rehabilitation programme. Score differences among the three samples were assessed controlling for age and gender and reliability coefficients are reported. The latent structure was studied in all samples, using exploratory and confirmatory factor analysis methods (EFA and CFA respectively).

The proposed structure was partially replicated via EFA. CFA however indicated less than satisfactory fit, as in previously reported results. To improve the fit, the path diagram was augmented to account for multiple factor complexity, as suggested by the EFA results in all samples. While retaining the original seven-factor structure, the augmented model provided adequate fit. The consistency of the inventory was satisfactory in all samples. Evidence for the construct validity was found in relation to aggression.

This is the first study to conclude in adequate fit, after allowing for the indicators to load on more than one factor within each dimension. While cross-national differences apply, our results were similar (when comparable) with previously reported ones in the literature.