Individual differences in cognitive performance are partly dependent, on genetic polymporhisms. One of the single-nucleotide polymorphisms (SNP) of the CNR1 gene, which codes for cannabinoid receptor 1 (CB1R), is the rs2180619, located in a regulatory region of this gene (6q14-q15). The alleles of the rs2180619 are A > G; the G allele has been associated with addiction and high levels of anxiety (when the G allele interacts with the SS genotype of the 5-HTTLPR gene). However, GG genotype is observed also in healthy subjects. Considering G allele as risk for 'psychopathological conditions', it is possible that GG healthy subjects do not be addicted or anxious, but would have reduced performance, compared to AA subjects, in attentional control and working memory processing. One hundred and sixty-four healthy young Mexican-Mestizo subjects (100 women and 64, men; mean age: 22.86 years, SD=2.72) participated in this study, solving a task where attentional control and working memory were required. GG subjects, compared to AA subjects showed: (1) a general lower performance in the task (P = 0.02); (2) lower performance only when a high load of information was held in working memory (P = 0.02); and (3) a higher vulnerability to distractors (P = 0.03). Our results suggest that, although the performance of GG subjects was at normal levels, a lower efficiency of the endocannabinoid system, probably due to a lowered expression of CB1R, produced a reduction in the performance of these subjects when attentional control and working memory processing is challenged.

TwinsMX is a national twin registry in Mexico recently created with institutional support from the Universidad Nacional Autónoma de México. It aims to serve as a platform to advance epidemiological and genetic research in the country and to disentangle the genetic and environmental contributions to health and disease in the admixed Mexican population. Here, we describe our recruitment and data collection strategies and discuss both the progress to date and future directions. More information about the registry is available on our website: https://twinsmxofficial.unam.mx/ (content in Spanish).

Attention allows us to select relevant information from the background. Although several studies have described that cannabis use induces deleterious effects on attention, it remains unclear if cannabis dependence affects the attention network systems differently.Objectives:To evaluate whether customary consumption of cannabis or cannabis dependence impacts the alerting, orienting, and executive control systems in young adults; to find out whether it is related to tobacco or alcohol dependence and if cannabis use characteristics are associated with the attention network systems.Method:One-hundred and fifty-four healthy adults and 102 cannabis users performed the Attention Network Test (ANT) to evaluate the alerting, orienting, and executive control systems.Results:Cannabis use enhanced the alerting system but decreased the orienting system. Moreover, those effects seem to be associated with cannabis dependence. Out of all the cannabis-using variables, only the age of onset of cannabis use significantly predicted the efficiency of the orienting and executive control systems.Conclusion:Cannabis dependence favors tonic alertness but reduces selective attention ability; earlier use of cannabis worsens the efficiency of selective attention and resolution of conflicts.

RESUMENIntroducción: la mariguana es la droga de mayor consumo después del tabaco y el alcohol, a pesar de que está penado utilizar más de cierto gramaje que depende del país; por ejemplo, en México es más de 5 g, lo que indica una alta motivación por conseguir la droga. Uno de los principios activos de la mariguana es el Δ9-tetrahidrocannabinol. Esta molécula afecta al sistema endocannabinoide, provocando cambios en su función y, concomitantemente, en la morfología cerebral. Objetivo: revisar y discutir la evidencia científica del efecto del consumo de mariguana sobre el cerebro, la inteligencia y la toma de decisiones. Método: se consideraron los reportes científicos que abarcan de 2005 a marzo de 2016 encontrados en PubMed, enfocados en los efectos del consumo de mariguana sobre cambios morfológicos cerebrales, la inteligencia y la toma de decisiones. Resultados: dependiendo de la edad de inicio del consumo de mariguana, es posible detectar cambios en el cerebro y la inteligencia, mientras que otras variables como la frecuencia o la cantidad de uso repercuten en la eficiencia para la toma de decisiones. Discusión y conclusiones: estos resultados señalan que 1) el consumo de mariguana afecta la morfología cerebral, la toma de decisiones y la inteligencia; 2) sugieren la potencial participación del sistema endocannabinoide en la toma de decisiones e inteligencia; y 3) dadas las consecuencias, deben alertar al sector salud para promover su prevención y en su momento estar preparados para la rehabilitación.Palabras clave: mariguana, inteligencia, adolescencia, sistema endocannabinoide, toma de decisiones. ABSTRACTIntroduction: marijuana or cannabis is the most consumed drug after tobacco and alcohol, even in the condition that to carry more than a given amount is a crime, suggesting that cannabis consumers are highly motivated to get the drug. In Mexico the amount allowed is 5g. Delta-9-tetrahydrocannabinol is one of the major psychoactive ingredient of cannabis. This molecule acts upon the endocannabinoid system, producing modifications in their function and, consequently, in the brain morphology. Objective: to review and discuss the scientific literature about cannabis consumption effect on brain, intelligence and decision-making. Method: the search of scientific reports in PubMed from January, 2005 to March, 2016, to evaluate the marijuana effect on brain morphology, intelligence and decision making. Results: it seems that as a function of the age of cannabis consumption onset the user might have morphological and functional brain changes, whereas variables such as frequency or amount of cannabis use may affect the efficiency of decision making. Discussion and conclusions: all these data together indicate that: 1) marijuana consumption affects brain morphology, decision-making and intelligence; 2) there is a potential role of the endocannabinoid system in decision-making and intelligence; and 3) given these consequences, should alert health organizations to develop strategies aiming prevention and if it is the...