Are Serotonin-Related Genes Involved in ADHD?

PostedOctober 7, 2025

UpdatedOctober 10, 2025

ByMy Patient Advice

Author: Victoria Rowe, MSc | Reviewed by: Dr. Rebecca Fernandez, MBBS

While dopamine and norepinephrine dominate ADHD research, growing evidence suggests that serotonin-related genes also play a role particularly in traits like impulsivity, emotional regulation, and mood instability. These traits often appear alongside core ADHD symptoms, especially in individuals with comorbid anxiety or depression.

5-HTT and Serotonin Transport

One key gene of interest is SLC6A4, which encodes the serotonin transporter (also known as 5-HTT). This protein regulates serotonin reuptake in the brain, affecting how long the neurotransmitter remains active in the synapse. A common variant, the 5-HTTLPR polymorphism, has been associated with altered emotional reactivity and may contribute to ADHD-related behaviours like impulsivity and difficulty with mood regulation.

Impulsivity and Comorbidity

People with certain serotonin gene variants may be more prone to impulsive decisions, low frustration tolerance, or heightened sensitivity to stress. These features do not define ADHD alone but are frequently seen in those with more complex or emotional symptom profiles, especially when comorbid anxiety, oppositional defiant disorder, or depression are present.

Although serotonin-related genes are not core to ADHD’s classic attentional pathways, they help explain emotional dysregulation and behavioural intensity in some individuals, broadening our understanding of ADHD as a neurodevelopmental disorder with diverse biological roots.

Conclusion

Serotonin genes like 5-HTT contribute to the emotional and impulsive traits often seen in ADHD, particularly in more complex or comorbid presentations.

Visit providers like ADHD Certify for personal consultations exploring the role of serotonin systems in ADHD symptoms.

For a deeper dive into the science, diagnosis, and full treatment landscape, read our complete guide to Genetic studies and biomarkers.

Victoria Rowe, MSc

Author

Victoria Rowe is a health psychologist with a Master’s in Health Psychology and a BS in Applied Psychology. She has experience as a school psychologist, conducting behavioural assessments, developing individualized education plans (IEPs), and supporting children’s mental health. Dr. Rowe has contributed to peer-reviewed research on mental health, including studies on anxiety disorders and the impact of COVID-19 on healthcare systems. Skilled in SPSS, Minitab, and academic writing, she is committed to advancing psychological knowledge and promoting well-being through evidence-based practice.

All qualifications and professional experience stated above are authentic and verified by our editorial team. However, pseudonym and image likeness are used to protect the author's privacy.

Dr. Rebecca Fernandez, MBBS

Reviewer

Dr. Rebecca Fernandez is a UK-trained physician with an MBBS and experience in general surgery, cardiology, internal medicine, gynecology, intensive care, and emergency medicine. She has managed critically ill patients, stabilised acute trauma cases, and provided comprehensive inpatient and outpatient care. In psychiatry, Dr. Fernandez has worked with psychotic, mood, anxiety, and substance use disorders, applying evidence-based approaches such as CBT, ACT, and mindfulness-based therapies. Her skills span patient assessment, treatment planning, and the integration of digital health solutions to support mental well-being.

All qualifications and professional experience stated above are authentic and verified by our editorial team. However, pseudonym and image likeness are used to protect the reviewer's privacy.