AD/HD symptoms usually surface when the child is between the ages of 3 and 6. Teachers tend to notice the symptoms before the parents, mostly because teachers observe the children in a more structured setting. Symptoms vary from child to child. Because of this it is possible that a diagnosis is not pursued until the child is older, sometimes even into adolescents. A late diagnosis can occur more often when the child has the inattentive type of AD/HD verses the hyperactive type.
The exact cause of AD/HD is unknown. Research suggests that AD/HD is caused by a developmental delay in the brain in which it handles neurotransmitters, like dopamine, serotonin, and adrenalin, differently than a normally developed brain. Research also suggests a possible link between AD/HD and mothers who smoked and/or drank during pregnancy. There is also a possible link between AD/HD and exposure to lead, which can occur if the child ever lived or frequently visited a building, which used lead paint or contained lead in the plumbing.
A highly debatable theory states that refined sugar and various food additives can cause AD/HD. Studies have shown that children who are given sugar show no difference in attention and activity than children who were given a sugar substitute. There has not yet been enough research conducted to prove or disprove that food additives could be a contributing factor to AD/HD.
AD/HD is hereditary. Children with parents that have AD/HD are 40-57% more likely to have AD/HD themselves. Researchers are in the process of trying to identify the specific genes that may cause AD/HD so that they can better diagnose it, treat the symptoms and may even be able to find ways to prevent symptoms from even surfacing. There is a certain gene identified that children with AD/HD have that causes thinner brain tissue in the area of the brain associated with attention. Studies have show that this tissue can thicken over time even improving AD/HD symptoms.