Abstract
Higher brain dopamine content depending on lower activity of Catechol-O-Methyltransferase (COMT) in subjects with high hypnotizability scores (highs) has been considered responsible for their attentional characteristics. However, the results of the previous genetic studies on association between hypnotizability and the COMT single nucleotide polymorphism (SNP) rs4680 (Val158Met) were inconsistent. Here, we used a selective genotyping approach to re-evaluate the association between hypnotizability and COMT in the context of a two-SNP haplotype analysis, considering not only the Val158Met polymorphism, but also the closely located rs4818 SNP. An Italian sample of 53 highs, 49 low hypnotizable subjects (lows), and 57 controls, were genotyped for a segment of 805 bp of the COMT gene, including Val158Met and the closely located rs4818 SNP. Our selective genotyping approach had 97.1% power to detect the previously reported strongest association at the significance level of 5%. We found no evidence of association at the SNP, haplotype, and diplotype levels. Thus, our results challenge the dopamine-based theory of hypnosis and indirectly support recent neuropsychological and neurophysiological findings reporting the lack of any association between hypnotizability and focused attention abilities.
Highlights
The cognitive trait of hypnotizability (Green et al, 2005) – the ability to accept hypnotic suggestions – has been classically attributed to peculiar characteristics of the supervisory attentional system (Norman and Shallice, 1986; Posner and Fan, 2004) allowing a more flexible attentional control in the subjects scoring high at hypnotizability scales
We found no evidence of association at the single nucleotide polymorphism (SNP), haplotype, and diplotype levels
Attention seems to be more efficiently controlled in subjects with the Met/Met or Val/Met variant of the single nucleotide polymorphism (SNP) rs4680 at the catechol-O-methiltransferase (COMT) gene than in the homozygous Val/Val individuals (Seamans and Yang, 2004)
Summary
The cognitive trait of hypnotizability (Green et al, 2005) – the ability to accept hypnotic suggestions – has been classically attributed to peculiar characteristics of the supervisory attentional system (Norman and Shallice, 1986; Posner and Fan, 2004) allowing a more flexible attentional control in the subjects scoring high (highs) at hypnotizability scales. Two of them (Lichtenberg et al., 2000; Raz, 2005) applied analysis of variance on the hypnotizability scores in subjects stratified by the COMT genotype In this approach, a sample of subjects not selected for hypnotizability ( representing the distribution of this trait in the general population) is genotyped, and ANOVA is used to test the differences of the mean hypnotizability scores among the genotypes. A sample of subjects not selected for hypnotizability ( representing the distribution of this trait in the general population) is genotyped, and ANOVA is used to test the differences of the mean hypnotizability scores among the genotypes Both studies reported a higher mean score of hypnotizability in heterozygotes (Met/Val) than in both homozygotes (Val/Val, Met/Met), but in one of them the association between hypnotizability and COMT polymorphism was significant in females only (Lichtenberg et al, 2000). The third study (Szekely et al, 2010) using the same approach reported intermediate hypnotizability scores in heterozygotes; these authors contrasted the highs and lows recruited in the sample for genotype frequencies, and found a significantly higher frequency of the Val allele among highs
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