As stated on our opening page, ADD and ADHD may or may not be actual biological conditions. There are many reasons to believe these labels are a social construction invented to describe biologically normal kids who are struggling to conform to the artificial demands we place upon them. But to the extent that these behavioral symptoms are caused by different things, scientists have turned up a number of risk factors that raise or lower the likelihood that a child will struggle with ADD or ADHD symptoms.

What causes ADHD or ADD?

Research has linked ADD and ADHD to both physical and environmental conditions:

Gender differences in ADD/ADHD
There are significant gender differences when it comes to rates of ADD and ADHD, providing strong evidence that we’re mislabeling children with a disorder for otherwise developmentally normal behavior. Boys engage in more aggressive and rambunctious behaviors in the classroom, whereas girls are typically quieter and better behaved. (Macionis, 2009, p. 81; Lilienfeld & Arkowitz, 2010) As a result, boys are far more likely to be slapped with the ADHD label, arguably just because they’re boys being boys.

The developmental trajectory is also slightly different between boys and girls. Though each child is different, girls on the whole typically develop much faster both physically and emotionally, whereas boys take their time. Maturationally speaking, girls may be a year or two ahead of boys throughout elementary school. This in and of itself could lead to higher rates of ADHD diagnosis, especially when considering the next factor I’m about to discuss.

Younger children are more likely to receive an ADHD diagnosis
The youngest children in the class are 60% more likely to be diagnosed with ADD than the oldest children, according to two separate studies published in the Journal of Health & Economics. Which is yet more evidence that leaves people like me skeptical we’re dealing with anything but a social phenomenon.

In 5th and 8th grade, the youngest kids in the class were more than twice as likely to have an ADHD diagnosis and use Ritalin as compared to the older kids. All told, it’s estimated that nearly 1 million children with fall birthdays may have been incorrectly diagnosed with ADHD simply because they’re younger than their peers. (Szabo, 8-17-2010)

This can then set off a self-fulfilling prophecy. John Rater, an associate clinical professor of psychiatry at Harvard Medical School, says teachers themselves may contribute to children developing ADHD by labeling them troublesome and treating them differently than their peers. (ibid) Which is yet more evidence the ADD & ADHD labels reside more in the environment than they do the child.

Media, technology & smart phones may be contributing to ADD & ADHD
“Since the advent of the smartphone, students in general have shorter attention spans and less impulse control.” -Sara Stevenson, a retired teacher (Wall Street Journal, 1-5-2019, p. A14)

Higher rates of media use have been consistently linked to higher rates of ADHD-like behavior in children and teens, such as trouble concentrating, difficulty completing tasks or having a hard time remaining still. A 2018 study in JAMA that tracked 2,500+ teens found that among the 500 or so teens with the lowest rates of media use, the prevalence of ADHD symptoms was 4.6%. Among the roughly 50 heaviest media users who reported daily use of all 14 types of media tracked, the rate was 10.5%, more than double. (Hernandez & Morris, 2018)

There are a couple possible explanations for this. First, it could be media use itself that’s contributing to these cognitive and behavioral issues. Digital devices promote a superficial style of interaction that features rapid hits and lots of distractions. We bounce around and swipe from one thing to the next in rapid fashion, nothing holding our attention for very long. It’s a type of high-stimulus yet shallow engagement that primes the brain to be easily distracted and bored in the absence of a lot of stimulus. Given the neuroplasticity of children and the amount of time kids spend on digital devices, it’s quite possible (likely, even) that digital media use in and of itself is changing children’s brains in a way that leaves them more susceptible to the behaviors typical of ADD or ADHD.

A second possibility is that media use is a proxy for other things. For example, increased screen time is also associated with less physical activity and less time spent outdoors, both of which have strong correlations to both cognitive impairment and behavioral problems. Excessive media use also crowds out other more developmentally productive activities, such as free play or human interaction. So those kids who spend the most time sitting behind screens would also tend to be the ones who get the least physical activity, spend the least time in nature, and are least engaged in free play or social interaction, all of which are linked to increases in ADHD-like behavior.

Lack of physical activity increases ADHD behavior
Humans, and children especially, were not designed to spend most of their days sitting still at a desk. Kids are meant to move, and when they aren’t physically active, a number of adverse consequences come about.

A lack of physical activity increases ADHD behaviors in two distinct ways. First, just as children who are cooped up all day will tend to be “bouncing off the walls” so to speak, prone to directing this pent-up energy toward disruptive behaviors, kids who aren’t getting enough physical activity tend to fidget more and engage in more disruptive behaviors, especially during times when they are bored, such as when asked to sit still at a desk and concentrate on things that don’t interest them.

Second, physical exercise isn’t just good for the body, it’s important for the brain as well. Physical activity increases blood flow to the brain, promotes neural growth, and raises levels of an important hormone called brain-derived neurotrophic factor (BDNF), which boosts memory and protects brain cells from damage. As a result, youth who are overweight and/or less physically active tend to struggle more in school. (Swer, et al. 2000)

Studies find the kids subjected to an “exercise intervention” exhibit more growth and activity in the frontal regions of the brain, an area important for executive function and impulse control. (Davis et al. 2007) Physical exercise has been linked to better attention and listening skills. (MLRC, 2002) It also boosts student’s concentration, reduces disruptive behaviors, and improves academic performance. (Coe et al., 2006; Hillman, Castelli & Buck, 2005; Sibley & Etnier, 2003; Dwer et al., 2001; Trudeau & Shephard, 2008) Those youth who exercise more exhibit more positive mood, are better able to manage stress, and display less type A behaviors. (Kircaldy & Shephard, 1990) All of these are things that would raise or lower the likelihood of a child being diagnosed with ADHD.

Nature deprivation & its links to ADHD in children
Time spent in nature is important for both the physical and psychological health of children. Those who spend more time outdoors have larger volumes of gray matter in their right prefrontal cortex, an area of the brain important for regulating emotions and impulse control. (Readers Digest, March/April 2022, p. 50) School children with a “green wall” or a window allowing plenty of natural light that overlooked green settings or who otherwise spend more time exposed to nature have fewer behavioral problems, improved discipline, fewer symptoms of ADHD, and they learn better and score higher on measures of intelligence and cognitive functioning. (Haupt, 2022; Wapner, 2008; Miranda, 2021)

When kids don’t spend enough time in nature, their mood and behavior suffers, leaving them more prone to the type of disruptive behaviors that increase the odds of them receiving an ADD or ADHD diagnosis.

Chemical exposures may cause ADD/ADHD
Chemicals and toxins of many varieties have been linked to neurodevelopmental disorders in children, including ADD and ADHD. Neurotoxins such as lead, mercury, cadmium and pesticides are especially likely to cause ADHD behavior, because they affect the brain in ways that diminish cognitive abilities while decreasing inhibitory control, precisely the type of formula that goes into ADD & ADHD symptoms. (See our information on chemicals and toxins for more details.)

Exposure to cigarette smoke can cause ADHD symptoms
Cigarette smoke is one of those toxins known to disrupt brain development, and it can be among the most significant. ‘Tobacco smoke and its residues are among the most important toxic environmental exposures to children, linked to health concerns from behavior problems such as ADHD to sudden infant death,” says Dr. Alan Greene. “The smoke contains over 250 poisonous gases, chemicals, and metals including hydrogen cyanide, arsenic, butane, toluene, lead, cadmium, and pelonium-210.” (Green, 2009, p. 126)

Smoking during pregnancy has an especially strong link to ADD and other behavioral problems. This is because cigarette smoke damages the placenta, starving the developing fetus of oxygen and other nutrients important for prenatal development. Kids born to mothers who smoked during pregnancy exhibit higher rates of cognitive impairment and are more prone to behavioral problems throughout their life. (Murkoff & Mazel, 2008)

Exposure to food dyes may cause ADHD
Some studies have linked artificial food dyes to increases in ADD-like behavioral symptoms in children. (See our separate page on food dyes & ADHD.)

References:

• Dwyer, T. et al.. (2001) “Relation of academic performance to physical activity & fitness in children.” Pediatric Exercise Science, 13, 225-237
• Haupt, A. (2023, April 3) “5 health benefits to house plants,” Time, p. 18
• Hillman, C.H., Castelli, D.M., Buck, S. (2005) “Aerobic fitness and cognitive function in healthy preadolescent children.” Medicine & Science in Sports and Exercise, 37, 1967-1974
• Kirkcaldy, B.D., Shephard, P. (1990) “Therapeutic aspect of leisure and sport.” Special edited Issue, International Journal of Sport Psychology, 21(3):: 165-184
• Miranda, G. (2021, July 21) “Study: Time in green spaces benefits kids’ mental health,” USA Today, 2D
• Sibley, B.A., Etnier, J.L. (2003) “The relationship between physical activity and cognition in children: A meta-analysis.” Pediatric Exercise Science, 15, 243-256
• Trudeau, F., Shephard, R.J. (2008) “Physical education, school physical activity, school sports and academic performance.” International Journal of Behavioral Nutrition and Physical Activity, 5(10), Feb. 25
• Wapner, J. (2008) ‘The best neighborhoods,” Psychology Today, Dec., Vol. 41(6):51
• Coe, D.. et al. (2006) “Effects of physical education and physical activity levels on academic achievement in children.” Medicine & Science in Sports and Exercise, 38, 1515-1519
• Davis, C. et al. (2007) “Effects of aerobic exercise on overweight children’s cognitive functioning: A randomized controlled trial.” Research Quarterly of Exercise and Sport, 78(5):510-19
• Green, A. (2009) Feeding Baby Green. San Francisco, CA: Jossey-Bass
• Hernandez, D., Morris, B. (2018, July 18) “Risk of ADHD grows with screen time,” Wall Street Journal, A3
• Lilienfeld, S., Arkowitz, H. (2010) “Are men the more belligerent sex?” Scientific American Mind, 21(2): 64-65
• Minnesota Learning Resource Center (2002) MLRC Report: A Chance to Grow. MLC, 1800 Second St. NE, Minneapolis, Minnesota, 554118, pp. 4-62, www.actg.org
• Szabo, L. (2010, Aug. 17) “Youngest in class get ADHD label,” USA Today, p. 1A