Psychomotor agitation and mood instability in patients with autism spectrum disorders: A possible effect of SLC6A4 gene?

•Analyses of clinical symptoms are promising for ASD genetic studies.•The results suggest particular genetic effects for males.•The SNP rs1042173 was nominally associated with psychomotor agitation.•A biased result was observed between the genotype LaLa and mood instability.

Autism spectrum disorders (ASD) are a group of neurodevelopmental conditions characterized by impairments in communication and social interaction and repetitive and stereotyped behaviors. Serotoninergic transmission has been suggested as an important neuronal pathway in ASD. In this study, we analyzed four polymorphisms (5HTTLPR, rs2066713, STin2, rs1042173; 5′ → 3′ end) at the serotonin transporter gene (SLC6A4) in a sample of 209 ASD children and their biological parents. Both single markers and haplotypes were tested for association with ASD diagnosis and with clinical symptoms (aggression, echolalia, seizures, mood instability, psychomotor agitation, repetitive behaviors and sleep disorders) commonly present in ASD patients. The family-based analyses showed a significant result for one haplotype (H4: S-G-12R-T), which did not hold in global analyses. In male patients, a nominal association between the rs1042173 GG genotype and a diminished psychomotor agitation was observed; a trend for an association between the 5HTTLPR LaLa genotype and mood instability was also verified. Through interesting results that are mainly related to clinical manifestations and gender differences, our study adds to knowledge of ASD. Future investigations may corroborate the relevance of our data to upcoming clinical and pharmacological interventions.