The causes of ADHD (Attention-Deficit/Hyperactivity Disorder) are complex and not fully understood, but research indicates that it primarily arises from a combination of genetic and environmental factors.
Genetic Factors
- ADHD is highly heritable, with genetics accounting for about 70-80% of the risk. It tends to run in families, meaning children with ADHD often have close relatives with the condition
- Multiple gene variants contribute to ADHD, each having a small effect. These genes affect brain development and neurotransmitter systems, especially those involving dopamine and noradrenaline, which are crucial for executive functioning and self-regulation
- Specific gene variants linked to ADHD include those affecting dopamine receptors (e.g., DRD4), dopamine transporters, and other neurotransmitter-related genes
Brain Development and Function
- ADHD is associated with differences in brain structure and function, particularly in the prefrontal cortex and executive networks responsible for attention, impulse control, and activity regulation.
- These brain regions often show reduced size, connectivity, and activation in individuals with ADHD, along with imbalances in dopamine and noradrenaline neurotransmission
Environmental Factors
- Various prenatal and early life exposures may increase the risk of ADHD, though they do not cause it directly. These include:
- Prenatal exposure to alcohol and tobacco smoke
* Exposure to environmental toxins such as lead and certain pesticides
* Premature birth, low birth weight, and oxygen deprivation around birth
* Brain injuries in early childhood
- Psychological trauma and adverse childhood experiences may also be associated with ADHD, though the exact relationship is unclear
Other Considerations
- ADHD is not caused by poor parenting, excessive sugar intake, or too much screen time, despite common misconceptions
- The interplay between genes and environment is complex; genetic factors can influence sensitivity to environmental risks, and vice versa
In summary, ADHD results from a multifactorial interplay of inherited genetic factors affecting brain development and function, combined with certain environmental exposures that may influence its expression
