Environmental factors can also influence the development and expression of ADHD symptoms.

Prenatal exposure to substances such as alcohol, nicotine, or drugs can increase the risk of ADHD in children.

Other environmental factors, such as lead exposure, low birth weight, and premature birth, have also been associated with an increased risk of ADHD.

While these factors alone do not cause ADHD, they can contribute to the overall risk when combined with genetic predispositions and neurobiological factors.