ADD/ADHD Medical Evidence
Medical Theory and Evidence for ADD/ADHD
The first evidence for the brain being understimulated was introduced with the use of more advanced electroencephalograms (EEG or brainwave studies) by Joel Lubar from the University of Tennessee. He demonstrated that when ADD children and teenagers performed a concentration task, there was an increased amount of slow brain wave activity in their frontal lobes, instead of the usual increase in fast brain wave activity that was seen in the majority of the control group.
PET data published in 1990 supported the notion of brain underactivity in the prefrontal cortex, especially in response to an intellectual challenge. Data from my own work with brain SPECT imaging drew the same conclusions. At rest, most ADD people have normal activity in their brain. When they perform a concentration task, however, they experience decreased activity in the prefrontal cortex, rather than the expected increased activity that is seen in a normal control group.
Tied to the decreased prefrontal cortex findings are the studies that indicate that ADD has a large genetic contribution, involving dopamine availability in the brain. A significant amount of dopamine is produced in the basal ganglia (large structures deep within the brain). Stimulant medications work by enhancing dopamine availability in this part of the brain.
Studies have demonstrated that the basal ganglia are smaller in people with ADD. The basal ganglia have a significant number of nerve tracks that go through the limbic system to the prefrontal cortex. It appears that when there is not enough dopamine available in the basal ganglia, then there is not enough "fuel" to drive the frontal lobes when they need to activate with concentration.
Beside the genetic contribution to ADD, maternal alcohol or drug use, birth trauma, jaundice, brain infections and head trauma (sometimes even minor ones, especially to the left prefrontal cortex) can play a causative role.
Notice decreased blood flow
and neuron activity
shown as black areas
(no activity, cold)
as person attempts
to focus and pay attention
|(Two brain images shown above courtesy
Daniel Amen, M.D., Amen Clinic, www.amenclinic.com)
ADDs and LDs are hypothesized to have low Acetylcholine levels and adverse lipofuscin populations within the cholinergic neural pathways, making a competitive response more difficult and trying. For both an ADD and LD individual, it becomes so "noisy" that it becomes necessary to shut down all processing of the senses altogether, avoiding and deflecting all stimulation.
The incessant cacophony of "neural-noises" produces a powerfully competitive "numbing," almost hypnotic agent, and ADHD individuals simply "give up" to the competitively powerful undifferentiated "white-neural-noise" being generated by their sensorium because the neural-thresholds of the sensorium have over-fired and can no longer be sustained. Thus, unlike other children, the ADD and LD individual simply "shut-down" and "tune-out," producing high Theta and/or Alpha brain waves (see brain maps below).
Relative Power Z-Score Maps from Quantitative Electroencephalography (QEEG)
Differences in Activity in Normal and ADD Children
The brain maps on the left (1&2) are of normal individuals: a 14-year-old female and 9 year old male. The ones on the right (3&4) are ADD individuals: a different 14-year-old female and a different 9-year-old male.
Notice how the two ADD individuals (3&4) demonstrate high (more red) Theta and Alpha activity in their maps than do the normal individuals, respectively. High Theta wave activity is generally associated with drowsiness; High Alpha activity is generally associated with idleness. The ADD results (3&4) are characteristic of states of non-attentiveness, and too little stimulation of the reticular activating system, and probable inadequate number of connections. Thus, the ADD/LD child can effectively "tune-out" his/her environment.
In contrast, the normal children's results of low Alpha and Theta wave activity (1&2) are characteristic of alertness and focused attentiveness, demonstrating adequate stimulation of the reticular activating system, and thus, an adequate number of neural connections.
There are many different areas of the brain that cause the ADD/ADHD symptoms.
The Reticular Activating System and Its Connections. At the Center of Consciousness, Attention and Learning.
The Reticular Activating System appears to be intimately involved in the neural mechanisms which produce consciousness and focused attention, receiving impulses from the spinal cord and relaying them to the Thalamus, and from there to the Cortex, and back again in a feedback loop to the Hippocampus/Thalamus/ Hypothalamus and participating neural structures in order for learning and memory to take place.
Without continual excitation of cortical neurons by reticular activation impulses, an individual is unconscious and cannot be aroused. When stimulation is enough for consciousness but not for attentiveness, ADD or LD results. If too activated, an individual cannot relax or concentrate (and is over-stimulated or hyperactive) often resulting in ADHD.
Abnormal functioning of the chemical systems within the brain.
People who have ADHD may have an imbalance of brain chemicals (such as dopamine, which helps control attention, and norepinephrine, which helps control activity).
Abnormal functioning of part of the brain (prefrontal lobe).
Areas of the prefrontal lobe in people with ADHD appear different from these areas in people who do not have ADHD. Special brain scans (positron emission tomography or PET) of adults with ADHD have indicated problems in the use of nutrients in the portion of the brain that controls attention and movement. However, results of these tests cannot be used to diagnose ADHD.
ADD is often associated with other conditions, such as learning, emotional, or behavioral problems. About one-third of children have more than one other condition along with ADD, such as oppositional defiant disorder (ODD), conduct disorder, anxiety disorder, or depression. The symptoms of these conditions are often mistaken for symptoms of ADD. Before the person can receive the greatest benefit from care for ADD, any other conditions need to be identified and treated.
What Causes ADD/ADHD?
It is believed that ADD may be caused by a combination of multiple factors, including genetic, biological, and environmental factors.
- Genetics. There is evidence that ADD is inherited. The genetic connection is between 75-91%.
- Alcohol, cigarette, or other drug use during pregnancy.
- Problems during pregnancy or delivery that cause injury to the brain. Infections that cause brain damage.
- Poor nutrition during a baby's first year of life.
- Lead poisoning.
- Head traumas, which impact the brain (need not cause loss of consciousness).