According to the Centers for Disease Control and Prevention (CDC), 15.6 percent of American boys and 8.2 percent of girls have been diagnosed with ADHD (but that discrepancy may be due to underdiagnosis in girls). Experts aren’t sure what causes ADHD. As is the case with most mental health conditions, it is thought to be an interplay of biological, social, and psychological factors
Neuroimaging studies using magnetic resonance imaging (MRI) scans to look at brain structure have found associations between certain neural circuits in the brain and ADHD. These circuits are related to sustained attention, control of inhibitions, motivation, and regulation of emotions.
Not all people with ADHD show the same circuits or changes in circuits, but certain brain differences are more common in people with ADHD than those without it.
Several factors may increase a child’s likelihood of developing ADHD.
Genetics
Environmental Exposure to Toxins and Chemicals
Although research has consistently shown a connection between lead exposure and ADHD, it’s important to note that it’s not the only cause of ADHD, nor does lead exposure guarantee that a child will develop ADHD.
Research has also found that other environmental toxins, such as bisphenol A (BPA), are potentially problematic for brain health. A 2025 systematic review concluded that exposure to endocrine disruptors, such as BPA, have an association with ADHD in children. However, more research is needed to clarify a causal relationship.
Alcohol or Tobacco Use During Pregnancy
A number of studies has found associations between tobacco use during pregnancy and ADHD symptoms in children. But more recent research has questioned whether substance use directly causes ADHD.
While a 2026 umbrella review of systematic reviews and meta-analyses published in the Journal of Psychiatric Research on smoking during pregnancy and its risk of ADHD on offspring did find an association, it concluded that evidence was lacking to establish a causal relationship. Rather, it suggests genetic and familial factors may be at play, and more high-quality research is needed to further investigate.
A 2022 meta-analysis and systematic review likewise found no clear causal link between prenatal smoking and ADHD diagnosis on offspring. It also noted more research is needed to investigate possible effects of alcohol consumption during pregnancy and ADHD risk for the child.
Still, pregnant people should refrain from alcohol consumption and smoking because of other well-established risks, including premature birth, low birth weight, and fetal alcohol syndrome.
Traumatic Brain Injury (TBI)
Premature Birth or Low Birth Weight
Some research has suggested that the lower a baby’s birth weight or the earlier their birth is, the greater the risk they have of developing ADHD.
Diet and Behavioral Factors
Excessive sugar or food additives in one’s diet and excessive screen time (television, smartphones, tablets, and computers) are associated with ADHD. For instance, one small study published in January 2022 in BMC Pediatrics suggested that certain eating patterns, such as high sugar consumption, were more common in children with ADHD than in those without ADHD.
While these factors may affect or exacerbate symptoms, research doesn’t support claims that they cause ADHD.
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