Attention-deficit hyperactivity disorder (ADHD) is characterized by impulsiveness, overactivity and an inability to maintain attention. Sufferers of the disorder may have significant difficulties in educational, social and occupational spheres. ADHD affects both genders. It usually manifests in early childhood and may continue throughout life. Many children appear to outgrow the disorder while other show symptoms into adulthood. There are several theories regarding the origin of this disorder; the causes of ADHD are not agreed upon as yet although many believe the causes will prove to be multifactorial.
Genetics
The National Institute of Mental Health reports that attention-deficit hyperactivity disorder is often present in one or more family members of a person who has the disorder. Scientists are currently conducting research to find which genes are at play in the development of ADHD. Some children with ADHD have a genetic variation that is evident on diagnostic scan, showing thinner brain tissue in the area of the brain responsible for focus and attention. Children with this type of genetic ADHD outgrow it as they develop.
Influences in the Womb
Maternal smoking and alcohol use have been implicated in the development of child ADHD. Illicit maternal drug use and exposure to environmental toxins, such as PCB (an industrial chemical) may also play a role in some cases.
Environmental Influences
PCB can negatively affect someone exposed to the chemical as an infant, leaving the person at increased risk of developing ADHD later in life. Mayo Clinic explains that preschoolers exposed to lead may develop the behavioral problems found in attention-deficit hyperactivity disorder. Formerly, this lead was often found in chipping paint or plumbing; today it is occasionally found in imported toys and other products that small children put into their mouths. Lead may continue to be a risk in some older buildings. While many think that ingestion of sugar may cause or exacerbate ADHD, the National Institute of Mental Health currently discounts this theory.
Brain Differences
The American Academy of Family Physicians reports that children with ADHD have a lower level of brain chemicals that coordinate thoughts. Differences in brain activity and structure have also been found in those with the disorder; in fact, the parts of the brain that control attention and activity show less activity than normal.
Brain Injury
Children who suffer a brain injury as an infant or preschooler are at increased risk of attention-deficit hyperactivity disorder. Brain injuries may be the result of an accident, a car wreck or child abuse. They can also happen because of medical reasons, such as a temporary lack of oxygen to the brain.
Prematurity and Low Birth Weight
Premature birth places a child at increased risk of ADHD. A report in "Medical News Today" indicates that babies born before 34 weeks gestation have triple the risk of developing the disorder later in life. Low-birth-weight babies born at full gestation also have increased rates of ADHD.
