What Causes ADHD?

Prenatal and Early Life Risk Factors of ADHD: What Research Says — and What Parents Can Do

What causes ADHD? Biological, genetic, and environmental factors — including prenatal and early life exposures — may play a role (and to varying degrees) in the condition’s development in children. But there is much left to uncover. Here, read an overview of the evidence, along with steps parents can take to protect their child’s health.

Is ADHD caused by birth trauma? Do prenatal complications increase a child’s risk for ADHD? What role do exposures during pregnancy and infancy play in the development of ADHD? These are all important — and difficult-to-answer — questions about the causes of ADHD that parents ask frequently.

From lead exposure and maternal stress during pregnancy to low birth weight, the list of prenatal and perinatal risk factors associated with ADHD seems to grow longer and longer with ongoing research. But there is much left to learn. The causal role of many exposures linked to ADHD is unclear; some appear to be artifacts of ADHD’s genetic element, while others are truly causal contributors. The other critical factor is that none of the risk factors cause ADHD every time; most children exposed to these risk factors do not develop ADHD.

Thus, it seems increasingly clear that genes and environments work together to shape development of the brain and behavior throughout life, but especially —and most dramatically — in very early life. ADHD, like other complex conditions, doesn’t have a single cause. Both nature and nurture influence its development.

Some prenatal and perinatal risk factors for ADHD are unavoidable and inevitable. Mothers grappling with their child’s ADHD diagnosis especially may place undue blame on themselves as they fixate on past events that could have contributed to their child’s ADHD. But science provides comforting truths: Exposure to risk factors does not guarantee ADHD, and early and effective treatment approaches can often mitigate the effects of previous complications and improve outcomes.

ADHD Risk Factors: What We Know

Prenatal Risk Factors

Teratogens: Alcohol, Smoking, and Other Substances

Teratogens are substances and agents that could harm a developing fetus during pregnancy. Some teratogens have been linked to ADHD, though association should not be mistaken for causality.

[Read: Is ADHD Genetic? Yes and No]


Children whose mothers consumed alcohol during pregnancy were at 1.55 times the risk for developing ADHD compared to children whose mothers did not consume alcohol while pregnant, according to a 2015 study of roughly 20,000 parents.1 Other studies have found mixed evidence on prenatal alcohol exposure and ADHD risk.2 3

Drinking alcohol during pregnancy can cause a group of conditions called fetal alcohol spectrum disorders (FASD), which are associated with some symptoms and features linked to ADHD, including behavioral challenges, inattention, learning disabilities, poor memory, hyperactivity, and impulsivity. 4

In many cases, FASD is overlooked altogether and even misdiagnosed as ADHD. 5 6

Tobacco Use

Maternal prenatal smoking increases risk for ADHD in children by more than one and a half times, according to a 2020 review of 12 large studies.7 Other studies have found that paternal smoking before and during pregnancy increases risk for ADHD in offspring.1 8 9

However, while smoking in pregnancy is a major correlate of ADHD, it’s probably not a causal factor. Studies that controlled for genetic effects found that the maternal smoking association to ADHD largely disappeared.

[Read: What Causes ADHD? Culture Vs. Biology]

Drugs and Other Substances
  • Opioids: Children whose mothers used opioids during pregnancy had more than double the risk for ADHD compared to those whose mothers did not use the drug, according to a 2022 study of about 3,000 children.2 The same study found that risk for ADHD increases with exposure to multiple substances, including tobacco and cannabis.
  • Acetaminophen exposure in the womb may increase a child’s risk for ADHD.10 It’s unclear whether there are time periods when the developing brain may be most sensitive to acetaminophen exposure. The FDA urges pregnant parents to consult with a doctor before taking pain medication.

But, as with smoking, we do not yet know if these effects are causal independent of genetic effects.

Maternal Health Issues

Maternal Metabolic Syndrome

Maternal obesity, hypertension, diabetes, and related conditions before and during pregnancy are associated with increased risk for ADHD, autism, and other neurodevelopmental disorders in offspring.12 13 While researchers are still investigating the connection, the risk for these effects in isolation appears small, especially considering the prevalence of these conditions at large. Still, they are effects that helps us learn about mechanisms that are possibly tied to ADHD.

Emotional Stress and/or Trauma

Maternal exposure to stress or trauma, if it’s high, can influence offspring behavior and temperament. What’s more, chronic prenatal stress increases the likelihood that a child will have ADHD or other conditions.

One 2018 study found that mothers who experienced high levels of stress during their pregnancy were more than twice as likely as less-stressed mothers to have a child diagnosed with ADHD or conduct disorder.14

Birth Trauma and Delivery Complications

Oxygen Deprivation

Insufficient oxygen supply and blood flow in utero and during birth is associated with increased risk for ADHD in later life.

Birth asphyxia is associated with a 26% greater risk of developing ADHD, while neonatal respiratory distress syndrome is associated with a 47% greater risk for ADHD, according to a 2012 study of more than 13,500 children with ADHD.15

C-Section Delivery

Compared to babies born via vaginal delivery, babies born via cesarean delivery (whether elective or emergency) are at greater risk for ADHD, according to a 2019 review of 61 studies comprising more than 20 million deliveries.16 The link between the two – including whether C-section delivery plays a causal role in the development of ADHD – remains unknown.

Prematurity and Low Birth Weight

Low birth weight and prematurity do appear to have a significant causal influence on the development of ADHD. Extremely preterm babies and those with very low birth weight are about three times likelier than healthy babies to develop ADHD, according to a 2018 meta-analysis of 12 studies involving 1,787 participants.17 Studies that controlled for genetics found the association still held.

ADHD Risk Factors: Events and Exposures in Early Life

Lead and Other Pollutants

Research on lead as a developmental neurotoxicant is robust. Its correlation with ADHD is also well established.18 Even low levels of exposure have an effect on ADHD.

Recent evidence suggests that lead has a causal role in ADHD. In our 2016 study, we looked at the effect of a common gene mutation – HFE C282Y – on the relationship between blood lead levels and ADHD symptoms in children, and found that children with ADHD who had the gene mutation exhibited greater symptoms of hyperactivity and impulsivity than did children with ADHD without the mutation.19

Because the C282Y gene helps to control the effects of lead in the body, and the mutation was spread randomly in the children, it is difficult to explain these findings unless lead is, in fact, part of the cause of ADHD, not just associated with it. Numerous animal studies also support a link.

As far as other pollutants, early exposure to nitrous dioxide and persistent organic pollutants has also been linked to ADHD, among others.20 21

Breastfeeding and ADHD

Breastfeeding is linked to decreased risk for ADHD in children.22 Mothers of children with ADHD are more likely than mothers of neurotypical children to report shorter breastfeeding duration.23 What underlies the ADHD-breastfeeding link is unclear, like whether breastfeeding protects the developing brain from ADHD, or if infants who are going to develop ADHD are more difficult to breastfeed and are thus breastfed for a shorter period of time. We used advanced statistical methods to test this in one study, and found that the causality was reversed: child ADHD caused reduced breastfeeding duration.

Head Injuries

Head injuries, especially severe traumatic brain injuries, increase risk for ADHD, according to a 2021 review of 24 studies that included 12,374 children.24

Head injuries and ADHD share a complicated chicken-and-egg relationship, as ADHD itself increases risk for head trauma.25 Children with ADHD are twice or three times as likely to obtain serious head injuries and accidental head injuries through their impulsivity.

Childhood Trauma

Children who experience trauma and who are exposed to adverse childhood experiences (ACES) are at increased risk for ADHD. The inverse is also true: ADHD increases the risk of exposure to trauma.26 27

Trauma is also known to exacerbate symptoms of ADHD. Compared to children without ADHD, children with ADHD who experience trauma are more reactive and sensitive to it, and need additional support.

Beyond a bi-directional relationship, trauma and ADHD share similar symptoms. It takes an experienced clinician to distinguish the conditions and understand if a child is experiencing a trauma effect or showing true signs of ADHD or both.

ADHD Risk Factors: The Bottom Line

Though research links a host of prenatal and early life risk factors to ADHD, it’s crucial to understand the following:

1. Few of these risk factors are yet known to be causal.

In most instances, we don’t yet know if risk factors have a causal effect or if it’s just artificial due to unmeasured correlates (in particular, genetic confounding). A key principle seems to be that the accumulation of multiple risk factors matters most in a child’s health. Genetic risk can be seen as one of the risk factors. But even a family history of ADHD doesn’t guarantee that a child will develop the condition.

2. Not all ADHD risk factors have equal influence.

Evidence for risk factors vary from “very strong” to “maybe.” Risk factors also tend to add up and occur in clusters, which ultimately makes it difficult to assess a factor’s relationship to ADHD. Some populations, including disadvantaged groups, may also be more vulnerable and sensitive to these risk factors or experience more of them.

3. To date, research has focused almost entirely on ADHD risk factors related to maternal health and pregnancy – but a dramatic shift is underway.

The history of psychiatry has unfortunately seen misguided blaming of mothers. It is important to realize that many of the risks are unavoidable, and that fathers are not off the hook. Paternal support, for one, can be a protective factor in maternal prenatal health and thus fetal health. But we are also learning more about how paternal exposures pre-pregnancy can affect sperm health and thus fetal health.

4. Exposure to a risk factor – even to a causal contributor of ADHD – does not guarantee an ADHD diagnosis down the line.

Most children who are exposed to these risk factors do not develop ADHD. There still has to be some other vulnerability or some other factors combined with these things in order for ADHD to emerge. In all, exposure to risk factors are rarely by themselves the entire explanation.

ADHD Risk Factors: What Parents Can Do

Exposure to ADHD risk factors may become a source of regret and second-guessing for parents. What I say to caregivers in this: Move forward; don’t belabor the past. Ultimately, at today’s level of knowledge, the cause of your child’s ADHD is not entirely known. More practical is to recognize that there is still a lot you can do to move forward positively.

If you are an expectant parent and/or the parent of a child with ADHD, follow these strategies below to minimize exposures, manage (and even reduce) your child’s ADHD symptoms, and protect your family’s health and wellbeing.

1. Engage in Behavioral Parent Training

ADHD can cause challenging behaviors that may overwhelm parents and lead to a negative parent-child dynamic — in itself a factor that can impact a child’s health and wellbeing. That’s why behavioral parent training (BPT) is an essential component of any child’s ADHD treatment. BPT teaches you how to respond to your child’s behaviors without inadvertently making those behaviors worse. Another benefit of BPT? It increases the chances that ADHD medication will work, and can lead to medication working at a lower dose.

2. Focus on Nutrition

Research has uncovered various links between nutrition and ADHD – some of which translate to actionable steps for your family.

  • Eat healthy foods during pregnancy. A 2018 study of about 1,240 mother-child pairs found that children whose mothers had a healthy prenatal diet were less likely to exhibit symptoms of hyperactivity over time than were children whose mothers had an unhealthy prenatal diet.28 Limit heavily processed foods and opt for whole, nutrient-dense foods.
  • Consider omega-3 supplements (1000 mg EHA/DPA a day). Children with ADHD tend to have lower omega-3 levels compared to children without ADHD, and supplementation modestly improves ADHD symptoms.29 Furthermore, prenatal omega-3 supplementation improved attention development in infants and toddlers in at least one controlled experiment.30
  • Try an elimination diet. Five percent to twenty-five percent of children with ADHD may see symptom improvement in response to a diet that eliminates common food allergens (cow-milk protein, soy, wheat, eggs, peanuts, seafood/shellfish) and additives (artificial food dyes and flavors).31 An elimination diet may be worthwhile if you suspect a dietary factor at play. But note that dietary changes are often difficult to implement. Your child may object, or the entire family may need to be involved. Adequate nutritional replacement also must be identified. Thus, only attempt this elimination plan in consultation with a behavioral counselor and nutritionist and/or your child’s pediatrician.
  • Opt for whole, unprocessed foods. Shop the perimeter of the supermarket for fresh, nutrient-dense foods. Avoid added sugars and caffeine, and try to keep your kitchen stocked with only healthy food choices.
  • Test for nutritional deficiencies. Children with ADHD are more likely than other children to have low levels of iron, zinc, and vitamin D.32 33 34 Supplementation can sometimes help with ADHD if nutrient levels are low. Recent evidence also suggests that specialized multi-nutrient supplements benefit important aspects of ADHD.35

3. Encourage Good Sleep Habits

Behaviorally-related sleep problems — from going to bed to falling and staying asleep — are common among children with ADHD. (True endogenous sleep disorders also occur at above chance levels in ADHD, but still are present only in a minority.36 ) Insufficient sleep, of course, worsens ADHD symptoms and functioning.

Create a bedtime routine, turn off or take away electronic devices before bed, and aim for your child to get 10 hours of sleep per night (depending on age). Talk to your child’s doctor to screen for potential co-occurring sleep disorders, or to get help with your child’s sleep problems.

4. Get Your Child Moving

Exercise improves health, mood, and ADHD symptoms.37 Exercise may even reverse some of the biological effects of past traumatic events on the body, as shown in animal studies.38 Children need at least one hour of moderate to vigorous exercise — be it sports, free play, or anything in between — on most days of the week.39

Nutrition, sleep, and exercise are healthy lifestyle factors with the clearest effect on ADHD symptoms. While they usually will not substitute for professional treatment, they may well reduce the stimulant or psychotherapeutic dosage your child needs.

5. Reduce Exposure to Lead and Other Pollutants

A lead test —for your child and for yourself, especially if you are pregnant or planning for it — is worth doing if you live in an area of high lead exposure. However, note that common medical lead tests do not detect the low exposure levels that have now been associated with ADHD in scientific studies. Thus, even if your child does not have detectable exposure, it is prudent to minimize lead exposure.

A healthy diet and sufficient levels of iron and vitamin D can help minimize the effects of lead (because of the way lead is metabolized).

Consider the following steps to address potential pollutant exposures at home and school:

  • Purchase a lead-removing water filter certified by an ANSI-accredited body.
  • Install HEPA-quality air filters.
  • If you live in home built before 1980, prevent and repair loose or chipped paint and do not let your child play in the soil right next to the house if possible.
  • Learn about various sources of lead exposure and how to protect your family.

6. Limit Screen Time and Watch for Quality

Though still a new area of research, findings from screen time research are cautionary. In a 2018 study, teens who spent excessive time on social media were more likely to exhibit ADHD symptoms after a two-year follow-up compared to teens who did not use social media as frequently.40

“Gaming addiction,” while still controversial, is receiving increased scrutiny. While more work is forthcoming, it remains possible that children with ADHD may be more susceptible to problematic video game play due to self-regulation challenges and the high-reward nature of gaming itself. Studies also link exposure to violent content with increased aggression in vulnerable children.41

7. Practice Self-Care

  • Manage stress and reduce stressors in your life. The more stressed out you are, the more stressed out your child will be, and the more you’ll get into a negative cycle. Social support and self-compassion are among the key elements for managing stress.
  • Recognize your own history of stress and trauma if present, and seek counseling and treatment if needed. Tell your doctor (and your child’s doctor) about your family’s experience with trauma, if any.
  • Eat a healthy diet, practice good sleep hygiene, and get exercise daily.
  • If you have ADHD, depression, or other mental health challenge yourself, stick to your treatment plan or talk to your doctor to see if an adjustment is necessary.

What Causes ADHD? Next Steps

The content for this article was derived, in part, from the ADDitude ADHD Experts webinar titled, “Genes and the Environment: How Biology and Exposures Contribute to ADHD in Children” [Video Replay & Podcast #433] with Joel Nigg, Ph.D., which was broadcast on November 30, 2022.

Thank you for reading ADDitude. To support our mission of providing ADHD education and support, please consider subscribing. Your readership and support help make our content and outreach possible. Thank you.

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