What Causes ADHD?
What Causes ADHD? Understanding the Bigger Picture
When parents or adults first hear the words attention-deficit/hyperactivity disorder, one of the first questions is:
“But what causes it?”
The honest answer is this: ADHD does not have one single cause.
It isn’t created by parenting style.
It isn’t caused by sugar.
It isn’t a lack of discipline.
ADHD develops from a complex mix of genetics and environment. Think of it less like flipping a switch and more like layering influences that shape how the brain develops.
The Strong Genetic Influence
Research consistently shows that ADHD runs strongly in families. Twin and adoption studies estimate that 60–90% of ADHD traits are influenced by genetics.
That doesn’t mean there’s one “ADHD gene.” Instead, many genes — each with small effects — likely work together.
Some of the genes studied are involved in regulating brain chemicals like dopamine and serotonin. Dopamine, in particular, plays a major role in motivation, attention, and reward processing. When dopamine systems function differently, attention and impulse control can be affected.
Researchers have identified several genes that may contribute to ADHD risk, but no single gene explains it all. Most evidence suggests ADHD is influenced by a combination of dominant and recessive genes interacting in complex ways.
In simple terms:
ADHD tends to be inherited — but it’s biologically layered and nuanced.
Genetic Conditions That Include ADHD Symptoms
Certain neurogenetic conditions are also associated with ADHD-like symptoms. These include disorders such as Tuberous Sclerosis, Fragile X Syndrome, Turner Syndrome, and others.
Even though these conditions are genetically different from one another, they may affect similar brain circuits involved in attention and impulse control. This overlap helps scientists understand that different biological pathways can lead to similar behavioral patterns.
However, routine genetic testing for ADHD is not currently part of standard clinical care.
Environmental Influences Before and After Birth
Genes create vulnerability — but environment can influence how that vulnerability unfolds.
Prenatal Factors
What happens during pregnancy can matter.
Research has linked the following to increased ADHD risk:
Prenatal alcohol exposure, which can affect brain structure and development.
Maternal smoking during pregnancy, which is associated with nearly a threefold increase in ADHD risk.
Smoking may interfere with dopamine regulation, which is already thought to play a central role in ADHD.
The more exposure, the higher the risk — suggesting a dose-response relationship.
Perinatal Factors
Events around birth may also contribute.
Very low birth weight has been associated with a twofold increase in ADHD risk. Complications during pregnancy and delivery are also reported more frequently in children later diagnosed with ADHD.
These factors may influence early brain development during a sensitive window.
Postnatal Factors
After birth, certain environmental conditions may further shape brain development.
Some research suggests possible links between ADHD and:
Imbalances in essential fatty acids (omega-3 and omega-6)
Iron deficiency
Early social deprivation
However, while these factors may contribute in some cases, they do not independently “cause” ADHD. The evidence here is still evolving.
The Interaction Between Genes and Environment
Perhaps the most important shift in understanding ADHD is this:
It’s not just genes.
It’s not just environment.
It’s how they interact.
For example, studies have shown that children with certain dopamine-related gene variants are more likely to develop the combined type of ADHD if they were also exposed to prenatal smoking.
In one study, males with a specific dopamine transporter gene variant showed higher levels of hyperactivity and impulsivity when exposed to prenatal smoke.
This is called a gene–environment interaction.
It means some children may be more biologically sensitive to environmental influences than others.
A Shared Biological Thread
Despite the complexity, one consistent finding across studies is altered dopamine transporter (DAT) functioning in many individuals with ADHD.
Dopamine helps signal motivation, interest, and reward. If dopamine signaling is less efficient, tasks may feel less engaging — and attention may drift toward stimulation that feels more rewarding.
This is why ADHD is not about laziness.
It is about how motivation and attention systems are regulated in the brain.
The Takeaway
ADHD develops from a spectrum of biological vulnerability shaped by genetics and environment.
It is not caused by:
Bad parenting
Lack of discipline
Too much screen time
It reflects differences in how certain brain systems develop and regulate attention, impulse control, and motivation.
Understanding this reduces blame.
And when we reduce blame, we create space for compassion, informed treatment, and realistic support.
ADHD is not a single path.
It is a convergence of many influences — meeting in one developing brain.