BackgroundAttention deficit hyperactivity disorder (ADHD) has a strong genetic component. The study is aimed to test the association of 34 polymorphisms with ADHD symptomatology considering the role of clinical subtypes and sex in a Spanish population.MethodsA cohort of ADHD 290 patients and 340 controls aged 6–18 years were included in a case–control study, stratified by sex and ADHD subtype. Multivariate logistic regression was used to detect the combined effects of multiple variants.ResultsAfter correcting for multiple testing, we found several significant associations between the polymorphisms and ADHD (p value corrected ≤0.05): (1) SLC6A4 and LPHN3 were associated in the total population; (2) SLC6A2, SLC6A3, SLC6A4 and LPHN3 were associated in the combined subtype; and (3) LPHN3 was associated in the male sample. Multivariable logistic regression was used to estimate the influence of these variables for the total sample, combined and inattentive subtype, female and male sample, revealing that these factors contributed to 8.5, 14.6, 2.6, 16.5 and 8.5 % of the variance respectively.ConclusionsWe report evidence of the genetic contribution of common variants to the ADHD phenotype in four genes, with the LPHN3 gene playing a particularly important role. Future studies should investigate the contribution of genetic variants to the risk of ADHD considering their role in specific sex or subtype, as doing so may produce more predictable and robust models.Electronic supplementary materialThe online version of this article (doi:10.1186/s12993-015-0084-6) contains supplementary material, which is available to authorized users.

An epidemiological study of inflammatory bowel disease in the Province of Granada, Spain, was conducted between 1979 and1988. Altogether, 257 cases were identified: 167 ulcerative colitis, 79 Crohn's disease, and 11 indeterminate colitis. The mean incidence of ulcerative colitis in the 10 year period was 2/105 and 0-9/105 for Crohn's disease. This is the first epidemiological study in Spain ofthe incidence of ulcerative colitis and corroborates the results of an earlier population based study on the incidence of Crohn's disease in Spain.

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Conclusions-Because of the phenotypic differences in the inflammatory infiltrate in the mucosa from the sigmoid colon and the rectum, the segment of the intestine to be biopsied should be specified. Assessment of the leucocytic component of the intraepithelial infiltrate in rectal biopsy specimens was more useful than examination of colonic biopsy specimens in the differential diagnosis of ulcerative colitis and Crohn's disease. (J Clin Pathol 1995;48:743-748)