Environmental factors in developing ADHD

It’s not just the circumstances surrounding pregnancy and birth that can affect ADHD outcomes — environmental factors can too. These can include harsh or intrusive parenting, experiencing trauma or hardship in early life, and exposure to certain chemicals.¹ A US study found a link between elevated levels of blood lead and symptoms of ADHD, for example.

And while there is some evidence that exposure to organophosphorus pesticides (OPP) during pregnancy could be associated with child ADHD, current evidence is mixed. A 2022 study found no increased rates of preschool ADHD in relation to levels of OPP in urine during pregnancy. This study was on an agricultural population exposed directly to the pesticides, rather than through eating fruit and veg grown with them – suggesting OPP exposure doesn’t have much of an effect on early-life ADHD risk.²

Research found that environmental factors (like those listed above) could have short-term effects on symptoms that lasted no more than a year (which happened over half the time). Or, they could have stable, trait-like effects that persisted long term.³ However, the study didn’t explore whether these effects continued into adolescence and adulthood – so exactly how persistent these environmental effects are isn’t clear.

Can Diet cause ADHD?

No, dietary factors don’t cause ADHD. But diet can affect behaviour and development, which can affect ADHD symptoms.⁴ There are two main kinds of studies that explore the relationship between ADHD and diet: supplement studies increase the amount of certain nutrients in your diet, and elimination studies remove certain foods from your diet.

Supplement Studies

The results surrounding supplemental studies are mixed, but there’s some evidence that nutrient supplements could help with ADHD symptoms. Lots of studies show that children with ADHD have nutrient deficiencies, so supplementing missing nutrients may help improve symptoms.

Amino acid supplements have shown some evidence of helping with ADHD symptoms, as they help with dopamine production and could improve cognitive function and memory. But there’s still limited evidence to support this, and more studies are needed.⁵

Low levels of minerals like magnesium and zinc have been reported in children with ADHD, and studies looking into the effects of zinc supplements have had promising results. A study found that patients taking zinc alongside ADHD medications had more improvement than those taking ADHD medication and a placebo. But further investigations using different doses of zinc were needed.⁶

Elimination Studies

Because of the impact diet can have on behaviour, studies have investigated the effect of eliminating certain foods that have adverse effects on ADHD symptoms. The first thing you probably think of when it comes to diet affecting ADHD symptoms is sugar – but a review looking into sugar’s effects on behaviour and cognitive performance in children found no adverse effects.⁷ It’s thought that the presumed relationship between sugar and ADHD may be indirect, as high or low blood sugar levels can affect attention.⁴

But research suggests artificial colours and preservatives could have an impact. One study looked into a sample of 1873 children screened at age three for hyperactivity, assessing them at baseline before removing all artificial colourings and benzoate preservatives from their diet for one week. After this week they were randomly given drinks containing artificial colourings and preservatives or a placebo mixture, and had their behaviour assessed. The study found less hyperactive behaviour during the withdrawal phase from preservatives and colourings, and significantly greater hyperactive behaviour after consuming artificial colourings and preservatives than after placebo.

This suggests that artificial colourings and preservatives could have an effect on hyperactive behaviour in children; but this increased hyperactive behaviour was only noted by parents, and not a clinical assessment. More research is still needed to collect stronger evidence.⁶

Psychological factors in developing in ADHD

There’s evidence that trauma can affect ADHD outcomes in children and adolescents, particularly traumatic brain injuries (TBIs). A selective literature review found that among individuals with no pre-existing signs of ADHD prior to the injury, a TBI is often followed by mental illness, especially ADHD (as well as changes to personality, anxiety, and post traumatic stress disorders).⁸

It’s thought that this link could be because persistent symptoms of TBIs include problems with memory and attention, difficulty with planning and organisation, and impulsive behaviour. It’s also been suggested that TBI could cause changes in the brain that can increase the risk of ADHD diagnosis.⁹

The review also points out that not many people who suffer a TBI in childhood get treatment for their mental health after injury. This highlights how important it is to monitor and support children following a TBI, to ensure they’re getting the treatment they need.⁸

Can an ADHD diagnosis help?

If you feel you or a loved one has been living with ADHD, a diagnosis can be really helpful. It can give you closure and reassurance, as well as get you on the right track to manage ADHD with prescription medication. Treatment can help improve attention span and behaviour in those with ADHD in different ways depending on the type used, and a clinician can recommend the most suitable kind for you. Speak to your doctor or an ADHD specialist for more information about a diagnosis.

Back to:

Overview

Genetic causes of ADHD

References:

1. Huhdanpää, H. et al. (2020). Prenatal and Postnatal Predictive Factors for Children’s Inattentive and Hyperactive Symptoms at 5 Years of Age: The Role of Early Family-related Factors. Child Psychiatry and Human Development. 52(5). pp. 783-799.

2. Manley, et al. (2022). Prenatal Exposure to Organophosphorus Pesticides and Preschool ADHD in the Norwegian Mother, Father and Child Cohort Study. International Journal of Environmental Research and Public Health. 19(13).

3. Livingstone, L.T. et al. (2017). Does the Environment Have an Enduring Effect on ADHD? A Longitudinal Study of Monozygotic Twin Differences in Children. Journal of Abnormal Child Psychology. 44(8). pp. 1487-1501.

4. Hjalmarsdottir, F. Arnarson, A. (2020). Does Nutrition Play a Role in ADHD? Healthline. January 30.

5. Rowden, A. Perez, A. (2022). Can L-tyrosine help with ADHD?. Medical News Today. May 31.

6. Batemen, B. et al. (2004). The effects of a double blind, placebo controlled, artificial food colourings and benzoate preservative challenge on hyperactivity in a general population sample of preschool children. Archives of Disease in Childhood. 89. pp. 506-511.

7. Wolraich, M.L. et al. (1995). The effect of sugar on behavior or cognition in children. A meta-analysis. JAMA. 274(20). pp. 1617-1621.

8. Schachar, R.J. et al. (2015). Mental Health Implications of Traumatic Brain Injury (TBI) in Children and Youth. Journal of the Candaian Academy of Child and Adolescent Psychiatry. 24(2). pp. 100-108.

9. McIntosh, James. (2015). New study supports link between ADHD and traumatic brain injury. Medical News Today. August 23.