Post #3: How Did I Get ADHD?

There are plenty of misconceptions about how ADHD is developed, but the research shows that there are actually very few reasons that a person has ADHD that are shown below. 

Most people never know exactly where their ADHD comes from, but that doesn't take away from our abilities to learn about our behaviors and thought patterns to live a productive life.

Genetics

Research has found that genetics is the most significant contributor to ADHD.1

#1: Through genetics, the most common way that ADHD appears is through inheritance from a parent. 25-35% of parents of ADHD children have ADHD themselves, 25-50% of siblings of children with ADHD have ADHD themselves, and 70-92% of identical twins both have ADHD.1

#2: The second way that ADHD can occur within genes is if there is a mutation in the genes of a child from a parent that does not have ADHD. This occurs in 10% of cases. These mutations occur in the gametes of the parent(s) from external factors such as: environmental toxins, sun exposure, or X-ray machines. There are many different factors that can cause gene mutation, as it is a normal process of gene development. 1

#3: The third way that ADHD can occur with genes is gene-by-gene interaction. This means that the more genes that a person has that are connected to ADHD the greater the possibility that the disorder will present itself by turning on other genes. 1

#4: The fourth way that ADHD can occur within genes is by gene-by-environment, which means an environment factor has triggered more genes to be expressed when there were already some genes present. This is common when the fetus is exposed to alcohol or tobacco during pregnancy which can increase the prevalence of ADHD by 2.5 times the population risk. If the fetus already has genes expressed that are associated with ADHD then that number will double. For example a fetus that has 1 gene associated with ADHD that is impacted with alcohol or nicotine will then have around 2.5 genes activated, but a fetus that has 5 genes associated with ADHD that is impacted in the same way will have around 12.5 genes expressed. Other environmental factors that can impact their genes are, but not limited to: exposure to infections, chronic elevated parental stress in pregnancy, adverse early environments like malnutrition or poor home life. 1

#5: The fifth way that ADHD can occur with genes is by epigenetics, which refers to the process of a gene being tagged as whether or not it will be activated. The messages behind this tagging comes from the parents but there is also research that environmental factors can also affect the tagging process as well. There still needs to be further research for this connection with genetics and ADHD, but hopefully more answers come out soon. 1

#6: The sixth way that ADHD can occur within genes is through major damage or duplication of the genes, or deletions to entire chromosomes that come from a genetic disorder. These are relatively rare events and are uncommon for most people with diagnosed ADHD. 1

About 65-75% cases of ADHD come from one of these six genetic circumstances.1

Neurologically Compromised Events

The other cases of ADHD come from some form of some form of Neurologically Compromised Events like: early brain injuries or maldevelopment alone with no genetic effects that occur when damage halts the development of certain brain areas related to ADHD traits like the prefrontal cortex, basal ganglia, and cerebellum. Most of these risks occur during infancy due to: significant prematurity of delivery, significantly low birth weight, exposure to multiple infections, maternal alcohol use, maternal tobacco use, toxins, maternal malnutrition, or maternal medical disorders.1

These cases contribute to about 15-25% of people diagnosed with ADHD.1

Other Causes

Other causes that occur after birth are head trauma, tumors, strokes, lead poisoning during the first few years of life, potentially dietary additives (still needs more research) or low levels of nutrients. 1

These cases contribute to about 5-10% of people diagnosed with ADHD. 1

Citation:

1 - Barkely, R. A. (2017) What Causes ADHD? https://russellbarkley.org/factsheets/WhatCausesADHD2017.pdf