Association of EEG alpha variants and alpha power with alcohol dependence in Mexican American young adults

Abstract

Several studies support an association between electroencephalogram (EEG) voltage and alcohol dependence. However, the distribution of EEG variants also appears to differ depending on an individual's ethnic heritage, suggesting significant genetic stratification of this EEG phenotype. The present study's aims were to investigate the incidence of EEG alpha variants and spectral power in the alpha frequency range in Mexican American young adults based on gender, and personal and family history of alcohol dependence. Clinical ratings (high-, medium-, and low alpha voltage variants) and spectral characteristics of the EEG in the alpha frequency range (7.5-12 Hz) were investigated in young adult (age 18-25 years) Mexican American men (n=98) and women (n=138) who were recruited from the community. Nineteen percent (n=45) of the participants had a low-voltage alpha EEG variant, 18% had a high-voltage variant, and 63% had a medium-voltage variant. There were no significant differences in the distribution of the EEG variants based on family history of alcohol dependence. There was a significant relationship between gender and the three alpha variants (chi2=9.7; df=2; P<.008), and there were no male participants with alcohol dependence with high alpha variants (chi2=5.8; df=2; P<.056). Alcohol dependence, but not a family history of alcohol dependence, was associated with lower spectral power in the alpha frequency range in the right (F=4.4; df=1,96; P<.04) and left (F=5.3; df=1.96; P<.02) occipital areas in the men but not in the women. In conclusion, in this select population of Mexican American young adults, male gender and alcohol dependence are associated with an absence of high-voltage alpha variants and lower alpha power in the EEG. These data suggest that EEG low voltage, a highly heritable trait, may represent an important endophenotype in male Mexican Americans that may aid in linking brain function with genetic factors underlying alcohol dependence in this ethnic group.

Lifetime history of traumatic events in a young adult Mexican American sample: Relation to substance dependence, affective disorder, acculturation stress, and PTSD

“…The lifetime prevalence of substance dependence in this sample and associations with acculturation stress and other comorbid mental disorders has been previously reported (Criado and Ehlers, 2007; Criado et al, 2013; Ehlers and Phillips, 2007; Ehlers et al, 2009, 2010, 2011, 2012, 2014; Gilder et al, 2007; Norden-Krichmar et al, 2014). Specifically, lifetime diagnoses of alcohol dependence, substance dependence, and anxiety disorders were associated with elevations in acculturation stress.…”

Endophenotype best practices

“…If a locus identified through GWAS shows different LD patterns in individuals of different ancestries, then conducting an association analysis in both ancestries can narrow the locus, thus reducing the set of credible candidate causal variants. For this reason, electrophysiological studies of different ethnic groups, such as those carried out with Native and Mexican American communities in the US (Ehlers & Gizer, 2013; Ehlers & Phillips, 2007; Ehlers, Wills, Phillips, & Havstad, 2015; Norden-Krichmar et al, 2015), are especially valuable even if they are not expected to greatly increase power to detect novel associations, nor do they obviate the need for large samples (e.g., see Table 3 ).…”

Genetic variation in FAAH is associated with cannabis use disorders in a young adult sample of Mexican Americans

“…Two previous studies have examined genetic variation in targeted ECS genes using a gene-based test; however, FAAH was not associated with cannabis use (Verweij et al, 2012) or cannabis dependence (Carey et al, 2015). This finding is not altogether surprising, given that these phenotypes differ from the construct used in the present study, and our MA subjects represent an ethnically unique sample at high risk for developing alcoholism (Criado and Ehlers, 2007; Ehlers and Phillips, 2007). Indeed most subjects with DSM-5 MSU had a comorbid DSM-5 alcohol use disorder.…”

“…Finally, as with other human genetic studies, replication is needed to support our findings. However, the exclusivity of the sample is both a strength and limitation; this sample is primarily of MA ancestry and has been previously shown to have a high risk of developing alcoholism (Criado and Ehlers, 2007; Ehlers and Phillips, 2007). …”