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Objective: The aim of this study was to investigate -1438A>G and T102C polymorphisms of serotonin 2A (5-HT2A) receptor gene frequencies in patients with Attention deficit hyperactivity disorder (ADHD) in comparison with a healthy control group and to determine the effects of these polymorphisms on the course and outcome of ADHD.
Methods: Fifty adolescent and young adults who were diagnosed with ADHD in childhood (between the years 1994 and 2001) were included in this study. Patients were followed in the Child and Adolescent Psychiatry Department of Gazi University Medical Faculty for 7–14 years, and they completed this follow-up period. The control group consisted of 50 adolescent and young adults, who were healthy physically and mentally. In adolescence and adulthood, the diagnosis was reached after semi-structured interview based on DSM-IV criteria. Ten milliliters of blood was taken from each participant. Genetic evaluation was performed with Polymerase Chain Reaction method. SPSS 11.5 was used for the statistical analysis. Categorical variables were analyzed with chi-square and Fisher-exact tests, while the independent t-test was used for continuous variables for two-category variables. Statistical significance was accepted as a p value of <0.05.
Results: a. Socio-demographic Features: In this study, 50 adolescents and young adults (39 male, 11 female; age range 16-25 years), who were diagnosed as having ADHD while childhood (age range at the time of diagnosis 6–10 years) and 50 healthy adolescents and young adults (33 male, 17 female; age range 16-25 years) were evaluated. In adolescence and young adulthood, the diagnosis of ADHD remained in 44 (88%) cases, whereas six (12%) had remission after the 7–14-year follow-up. b. Relationship of the 5HT2A receptor gene T102C and -1438 A>G Polymorphisms with ADHD: A significant difference in the frequency of CC, CT and TT genotypes of T102C polymorphism (χ2:1.629, p: 0.44) and AA, AG and GG genotypes of -1438A>G polymorphism (χ2: 0.065, p: 0.96) was not found between the ADHD and control groups. A significant difference was not found between patients with ADHD with CC, CT or TT genotypes in terms of the outcome of illness (χ2:0.114, p: 0.94). Similarly, there was no difference between patients with ADHD having AA, AG and GG genotypes in outcome terms (χ2:0.530, p: 0.76).
Conclusion: A significant association between -1438A>G and T102C polymorphisms of 5-HT2A receptor gene and ADHD was not found in the present study. A significant effect of these two polymorphisms on the outcome of ADHD in adolescence was not detected. The results of this study do not support a role for the serotonergic system in the development and course of ADHD. As this study including children diagnosed as having ADHD in their pre-school and primary school periods evaluated in adolescence and adulthood periods, and was a follow-up investigation, the sample size was limited.