Evidence gained from animals and humans suggests that the encephalic opioid system might be involved in the development of drug addiction through its role in reward. Our aim is to assess the influence of genetic variations in the opioid receptor mu 1 on alcohol and tobacco consumption in a Spanish population. 763 unrelated individuals (465 women, 298 men) aged 18-85 years were recruited between October 2011 and April 2012. Participants were requested to answer a 35-item questionnaire on tobacco and alcohol consumption, as well as to complete the AUDIT and Fagerström tests. Individuals were genotyped for three polymorphisms in the opioid receptor mu 1 (OPRM1) gene, using a TaqMan® protocol. In males, the rs10485057 polymorphism was associated with total pure ethanol intake and with the risk of being an alcohol consumer. Also, this polymorphism was significantly associated with higher Fagerström scores. Rs1799971 had a different influence on adaptive and maladaptive patterns of alcohol use. Despite the limited sample size, our study might enrich current knowledge on patterns of alcohol use, because it encompasses both extreme and adaptive phenotypes, providing thus a wider perspective on this subject.

Background and Objectives: There is adherence to a healthy Mediterranean diet (MedDiet), but adherence varies widely. Precision nutrition is increasingly interested in individual characteristics influencing diet adherence, but few studies have examined personality traits. Our main aim was to investigate the association between personality traits and MedDiet adherence. Our secondary aims were to explore genome-wide genetic variants associated with neuroticism, including replication of previous findings, as well as to explore gene–MedDiet interactions. Methods: We analyzed participants (aged 55–75) in the PREDIMED-Plus-Valencia study and measured clinical, lifestyle, and genetic factors. The Eysenck Personality Questionnaire-Revised (EPQ-R) was used to measure neuroticism, psychoticism, and extraversion. Genotyping was undertaken, and associations with candidate SNPs, genome-wide association studies (GWAS), genetic risk scores (GRS), and gene–MedDiet interactions were explored. Results: Neuroticism was inversely (beta = −0.09; p = 0.001) associated with adherence to the Mediterranean diet (MEDAS-17). Likewise, the probability of low MedDiet adherence increased neuroticism (OR: 1.27; 95% CI: 1.02–1.60; p = 0.031 per SD). In the GWAS for this trait, several SNPs surpassed the suggestive level of statistical significance. The most strongly associated was rs10181407-NDUFA10 (NADH dehydrogenase 1 alpha subcomplex subunit 10) (beta = −2.39; p = 2.70 × 10⁻⁶). The GRS for neuroticism was significantly associated with MedDiet adherence (beta = −0.18; p = 0.020), increasing the causality level. We replicated some candidate SNPs, and among them, the rs2243873-EHMT2 (euchromatic histone lysine methyltransferase 2) gene. The analysis of gene–MedDiet interactions revealed the role of these dietary modulations. Conclusions: Neuroticism was the personality trait most inversely associated with MedDiet adherence, suggesting its integration in precision nutrition analysis. Moreover, neuroticism-related genetics and MedDiet modulations will also be important.