It has been suggested that the features of childhood ADHD are significantly associated with adult mood disorders. Some genetic factors may be common to both ADHD and mood disorders underlie the association between these two phenotypes. The present study aimed to determine whether a genetic role may be played by the serotonin transporter-linked polymorphic region (5-HTTLPR) in the childhood ADHD features of adult patients with mood disorders.

The present study included 232 patients with MDD, 154 patients with BPD, and 1288 normal controls. Childhood ADHD features were assessed with the Korean version of the Wender Utah Rating Scale. The total score and the scores of three factors (impulsivity, inattention, mood instability) from the WURS-K were analyzed to determine whether they were associated with the 5-HTTLPR genotype.

In the BPD II group, the 5-HTTLPR genotype was significantly associated with the total score (P = 0.029) and the impulsivity factor (P = 0.004) on the WURS-K. However, the inattention and mood instability factors were not associated with the 5-HTTLPR genotype, and the MDD and normal control groups did not exhibit any significant associations between the WURS-K scores and the 5-HTTLPR genotype.

The present findings suggest that the 5-HTTLPR genotype may play a role in the impulsivity component of childhood ADHD in patients with BPD II. Because of a small sample size and a single candidate gene, further studies investigating other candidate genes using a larger sample are warranted to more conclusively determine any common genetic links.

The author has not supplied his declaration of competing interest.