ADHD is a neurodevelopmental disorder that children and also adults can develop. A complex interplay of genetic and environmental factors may underlie interindividual variability in ADHD and potentially related aggressive behavior. Using high-resolution molecular biology techniques, we investigated the impact of some MAOA and SLC6A4 variations on ADHD and aggressive behavior in a group of 80 Italian children with ADHD and in 80 healthy controls.We found that homozygous genotypes of MAOA rs6323 and rs1137070 were associated with an increased risk of ADHD (p=0.02 and p=0.03, respectively), instead the heterozygous genotypes (GT of rs6323 and CT of rs1137030) (p=0.0002 and p=0.0006) were strongly linked to a lower risk of developing this disorder. In patients with aggressive behavior, we highligted only a weak negative association of both MAOA polymorphisms (heterozygous genotypes) with aggressiveness then, suggesting that these genotypes maybe protective towards specific changes in behavior (p=0.05). Interestingly, an increase of the GG genotype of rs6323 (p=0.01) and a decrease of GT genotype (p=0.0005) was also found in patients without aggressive behavior compared with controls. Regarding 5HTT gene genotyping, no allele and genotype differences have been detected among patients and controls. Our work shows that defining a genetic profile of ADHD may help to early detect those patients who are more vulnerable to ADHD and/or antisocial and aggressive behavior and to design precision-targeted therapies.

Antisocial behavior is a behavior disorder inherited according to the inheritance of X-linked chromosome. This disorder derives from mutations in the MAOA gene. One of the mutations results in the MAOA-L allele activity. The MAOA-L allele activity can cause antisocial behavior in both healthy and unhealthy people. Antisocial behavior from healthy males can originate from maltreatment during childhood. Currently, MAOA inhibitor can reverse antisocial behavior to normal behavior in animal models. However, this disorder cannot be treated permanently; to treat it permanently in the future, technologies such as CRISPR/Cas9, iPSCs and ssODN are required. These technologies have succeeded to correct erroneous segments in the F8 gene and F9 gene. Both genes occupy the X chromosome. The MAOA gene also occupies the X chromosome. Therefore, it is reasonable to state that CRISPR/Cas9 and iPSCs technique for instance can be beneficial tools to edit the MAOA gene to treat antisocial behavior. CRISPR/Cas9 can be used in combination with iPSCs or ssODN for instance. This combination can greatly help the permanent healing of antisocial behavioral disorders.