Although there is yet to be a specific cause of ADHD, there are about three or so causes that have been concluded to bring about ADHD they are:
Genetic Causes: ADHD is said to have been hereditary and this is a fact in about three quarter of the cases of children diagnosed with it. According to research, when the transporters in the brain, known as dopamine, are affected due to a combination of several genes, then ADHD arises. One of the genes, known as LPHN3, is primarily more dominant than the rest is the major cause of most of the ADHD cases. The LPHN3 is said to respond well to medication that is stimulant.
Environmental Causes: According to the twin research study, about nine to twenty percent of the ADHD symptoms have been brought about by some environmental factors, such as exposure to tobacco smoke or alcohol exposure to women who are expectant, and these factors are thus non-genetic and non-shared. Exposure to lead compounds during a person’s early life has also been termed as one of the environmental factors that have led to the ADHD symptoms. Tobacco smoke's relation to ADHD symptoms is due to hypoxia, which is caused by nicotine that makes the fetus in the utero not have enough oxygen supply. Another cause would be because most women that suffer from ADHD tend to have a smoking habit so the component of genes is stronger thus transferring it to their children. Those children that have had infections and viruses like varicella, enterovirus 71, measles and rubella, during and before birth, also in their childhood, are said to be at a higher risk of developing the ADHD symptoms hence ending up being diagnosed with it.
In the year two thousand and seven, a study was done and it was concluded that an insecticide, called chlorpyrifos, which is used in various fruits causes reduction in a person's coordination physically and leads to some behavioural changes/problems found in children with ADHD.
Another study that was done in the year two thousand and seven found out that children who are exposed to pesticides are at a higher risk of getting ADHD. In the analyzation of this study, the urine of over a thousand children was taken for lab testing, and it was found that the urine of the children that had high incidences associated with ADHD contained the phosphates known as dialkyl, which is a product breakdown of a pesticide known as Organophosphate. In conclusion it was found out that there was a thirty five percent possibility of the other children, who had no symptoms of ADHD, contracting it due to the presence of the same pesticide concentration in their urinary residue. This was seen to be possible in even those children that had the lowest level of the pesticide concentration in their urine.
There were three studies that were longitudinal and funded by the government in the year 2010-2011 to examine the exposure of children in grade school to the pesticides known as Organophosphate from pregnancy. Although there were different techniques that were used in determining the amount of exposure the children had had, the conclusions that were reached were all the same. The conclusion was that those children that had been exposed during pregnancy, showed signs of having low intelligence quotient, and also found difficulty in focusing and solving problems. One of those studies indicated that although the exposure to these pesticides contributes to the ADHD symptoms, genetics was still the core cause of ADHD in children. The other two studies showed that children that had been diagnosed with a high ADHD rate were those that had been exposed to high Organophosphate levels.
Diet Related Causes: The Lancet, published a study that had been done and it was found that there was a link between the ingestion of artificial colours for food, sodium benzoate preservative and hyperactivity. In light of this discovery, the Government of Britain took immediate action like making the end of the year 2009 the deadline for manufacturers of artificial colours for food to stop their making. Following this action, food colours that contained Carmoisine (E122), Yellow FCF (E110), Allura red (E129), Ponceau 4R (E124), Tartrazine (E102) AND Quinoline yellow (E104), should all contain labels of warning on top of the packaging. This was a rule that was put in place by the European commission. In the month of march, the year 2011, the US FDA did an evaluation of possible evidence of a scientific link between ADHD and dyes and the final result was that there was no link.
The Food, Drug and Cosmetic Act of the US has a requirement that artificial colours for food should have received an FD&C number from the FDA before they are used for consumption/ before they are sold. This act also requires an indication of the use of any colours for food.