SLC6A4 and autism: As the genetic marker rs25531—modulating the effect of 5‐HTTLPR on the SLC6A4 gene's mRNA levels—to our knowledge has not been investigated so far in the 5‐HTTLPR–autism research, we examined the associations between genetic markers (5‐HTTLPR/rs25531) and individual differences in autistic traits in two samples with different ethnic background stemming from China and Germany.