Association between CLOCK gene polymorphisms and ADHD in Mexican teenagers: A comprehensive assessment.

This study aimed to evaluate markers of the CLOCK gene rs1801260 and rs4864548 in Mexican adolescents, addressing clinical and biological aspects previously associated with ADHD. 347 Mexican adolescents were assessed for mental disorders, metabolic disruption and related conditions, circadian preference, as well as genotyping for the CLOCK. We found a significant association between ADHD and the AA and AG genotypes of rs1801260. Also, we identified in the ADHD group that the total Triiodothyronine and total Thyroxine values were respectively 10 ng/dl units and 0.58 ug/dl units lower in females than in males. Previously reported common variations of the CLOCK gene have been associated with ADHD like the Rs1801260 polymorphism hereby we could consider it as risk factor, but genetic, biochemical and clinical studies in the Mexican population are entailed.

After a disaster: Validation of PTSD checklist for DSM-5 and the four- and eight-item abbreviated versions in mental health service users.

Posttraumatic stress disorder (PTSD) is a common and disabling condition developing in one of four survivors after an earthquake. Brief and self-reported validated measures for assessing PTSD symptom severity are necessary to improve care access and assess disorder progress and treatment response. Therefore, we evaluated the psychometric properties of the PTSD-Checklist for the DSM-5 (PCL-5) of 20-, 8- and 4-item in patients that sought specialized mental health services after a catastrophic earthquake that stroke Mexico on September 19th, 2017. The internal consistency of 20-, 8- and 4-item PCL-5 was adequate (≥.7). Using the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) as a reference, signal detection analyses revealed a PCL-5 score of 27 as optimal (sensitivity = .96, specificity = .73) for identifying probable PTSD cases. The shortened versions highly correlated with the full PCL-5 and had comparable diagnostic utility. Our results indicate that the 20-item PCL-5 and the abridged versions can effectively identify possible PTSD cases. The 8-item version has better psychometric properties and more consistent diagnostic utility across time and civil populations. These measures must be evaluated in independent samples to corroborate their utility in different populations and regarding diverse traumatic events.

Haplotype and nucleotide variation in the exon 3-VNTR of the DRD4 gene from indigenous and urban populations of Mexico.

OBJECTIVE: To describe the population structure of the 48-bp variable number of tandem repeats (VNTR), located in exon 3 of the dopamine receptor D4 gene (DRD4), in 41 Tarahumara from northern Mexico, 20 Mixe from southern Mexico, and 169 people from Mexico City. METHODS: Genotypes for the DRD4-VNTR were determined, from which 15 Tarahumara, eight Mixe, and 37 urban homozygous individuals were sequenced. Repeat-allele frequencies were compared with other world populations. RESULTS: The DRD4-VNTR variation in Mexico City appeared similar to the world mean. For the Mixe and Maya, DRD4-VNTR diversity appeared closer to South American groups whereas the Tarahumara were similar to North American groups. People from Mexico City and the Mixe exhibited attributes of a large and admixed population and an isolated population, respectively. The Tarahumara showed endogamy associated with a substructure as suggested by a preliminary regional differentiation. For the DRD4-VNTR and/or the adjacent 5'-173 bp sequence, the three populations exhibited negative Tajima's D. Two new VNTR haplotypes were discovered: one in Mexico City and another among the Tarahumara. CONCLUSIONS: A differentiation in the DRD4-VNTR of global relevance occurs between northern and southern populations of Mexico suggesting that the Mexican Trans-volcanic Belt has been a major frontier for human dispersion in the Americas. Ancient trespass of this barrier appears thus related to a major change in the population structure of the DRD4-VNTR. Distinctive and independent patterns of DRD4-VNTR diversity occur among the two Mexican indigenous populations by a still undefined combination of drift and selection.

Estudio de la variabilidad genética del DRD4 y del DAT1 en individuos habitantes de la Ciudad de México / Genetic variability study of DRD4 and DAT1 in the urban population of Mexico City

Family, twin and adoption studies suggest that genetics plays an important role in the etiology of many psychiatric disorders. It has been proposed that the dopaminergic brain system could be affected in schizophrenia, substance abuse and attention deficit hyperactivity disorder. The most studied genes are two VNTR polymorphic systems; one located in the exon 3 of the dopamine D4 receptor (DRD4) gene, and the other in the 3' untranslated region of the dopamine transporter (DAT1 or SCLA6A3) gene. It has been reported that allele frequencies of these polymorphisms varied between populations and this could affect the results in the association studies. Due to the previous findings, the objective of the present study was to determine the allele frequencies of DRD4 and DAT1 in an epidemiological sample of the adolescent population of México City. We found that the frequencies presented in our study were in between those reported for Caucasians and those reported for the American Indigenous population, this result are consistent with Euro-Indigenous inbreeding that has occurred in Mexico. Moreover, the results presented in the present study could explain the lack of consistency in the association analysis and make necessary to develop these investigations in our population.

Existe evidencia fehaciente de la influencia genética en los trastornos psiquiátricos y se ha propuesto que el sistema dopáminergico cerebral puede ser uno de los afectados en diversos trastornos como la esquizofrenia, el abuso de sustancias y el trastorno por déficit de atención e hiperactividad. En este sentido, los sistemas genéticos más estudiados son 2 VNTRs; uno localizado en el exón 3 del gen del Receptor a dopamina D4 (DRD4) y el otro en la región 3' no traducida del transportador a dopamina (DAT1 o SCL6A3). Se ha reportado que las frecuencias alélicas de estos polimorfismos difieren significativamente entre poblaciones y que esto puede afectar los resultados en los estudios de asociación. Debido a lo anterior, el objetivo del presente trabajo fue determinar las frecuencias alélicas del DRD4 y del DAT1 a partir de una muestra epidemiológica de la población adolescente de la Ciudad de México. Las frecuencias alélicas reportadas en el presente estudio son intermedias a las reportadas en caucásicos y poblaciones indígenas de América, lo que concuerda con la historia de mestizaje ocurrida en México. Estás diferencias pueden ayudar a explicar la falta de consistencia en diferentes estudios de asociación y hacen necesario realizarlos en población mexicana.