Changes in the serum levels of brain-derived neurotrophic factor in adults with attention deficit hyperactivity disorder after treatment with atomoxetine.

Rationale: Atomoxetine (ATX) is a non-stimulant drug approved for the treatment of attention deficit hyperactivity disorder (ADHD). Although animal models have provided evidence that brain-derived neurotrophic factor (BDNF) is involved in the effects of ATX in the brain, there are no studies of BDNF in ADHD patients undergoing treatment with ATX.

Objectives: The aim of this study was to evaluate the possible changes in serum levels of BDNF in adults treated with ATX and its relationship with clinical improvement.

Methods: A total of 54 adults with ADHD (age 33.43 ± 8.99 years) without any medical or psychiatric comorbidities were treated with ATX for 3 months; 35 of them completed the protocol. The clinical data for ADHD diagnosis, including Conners' ADHD Rating Scale and blood samples, were collected at baseline (V1) and at the end of the treatment (V2).

Results: Adults with ADHD who completed ATX treatment for 3 months showed a significant improvement in their clinical symptoms. No significant differences were found in BDNF levels before and after treatment with ATX in the whole group of patients (p = 0.15). The inattentive subgroup of ATX responders showed a decrease of serum BDNF after 3 months of ATX treatment (p = 0.05) not present in the combined subtype (p = 0.82).

Conclusions: These results suggest that BDNF is not directly involved in the neurobiological mechanisms of ATX-induced improvement of clinical symptoms of ADHD. The differences between the combined and inattentive subtypes in serum BDNF changes suggest selective ATX-induced effects in the function of brain circuitry.