ADHD

 

What Causes ADHD?


ADHD is a disorder of the mind, affecting attention, behavior, and other so-called “higher mental functions.”  As such, its underlying cause is complex and not completely understood.


The human brain

The brain is responsible for controlling most aspects of bodily and mental function.  Medical researchers long ago discovered that different parts of the brain controlled different functions, such as muscle movement, detection of sounds heard through the ears, and psychologic and behavioral capacities such as emotion, memory, and social interactions.  All of these jobs are coordinated through a complex system of neurons, which communicate with each other through chemical signals called neurotransmitters.  Some common neurotransmitters found in the brain and elsewhere in the body include epinephrine (also known as adrenaline), norepinephrine, dopamine, serotonin, and many others.

The basic abnormality in ADHD is related to an imbalance of the levels of various neurotransmitters (particularly norepinephrine and dopamine) in the areas of the brain that control complex thoughts and behaviors such as knowing right from wrong, understanding the consequences of actions, personality traits, and more (mostly the prefrontal cortex and connections in the basal ganglia).


In these PET scans (a type of radiologic imaging),
the brain of the ADHD patient (right) shows less activity,
especially in the frontal areas (top of the image)
compared with the non-ADHD patient (left).


So what causes ADHD?

Genetics plays a big part in the development of ADHD. The first-degree relatives of a person with ADHD are up to 8 times more likely to have ADHD than the general population. Of course, the disease is not entirely familial. More likely, ADHD develops when a genetic predisposition is mixed with a set of environmental circumstances. Though researchers have not fully worked out what those factors are, theories include toxin exposure during brain development in the womb, some commonly used food colorings, or hypersensitivity to environmental allergens. In short, besides family history, we really have no good way of predicting which kids will develop ADHD until the symptoms begin to appear.


Family history is one of the
strongest links to ADHD


What Doesn’t Cause ADHD?

Despite the abundance of circulating myths, excessive consumption of sugary foods has no association with ADHD.  Despite substantial research, no dietary factors have been found to be responsible for causing ADHD.  Likewise, no amount of “bad parenting” will cause a child to develop ADHD, nor will “good parenting” prevent ADHD.  As stated above, genetics provide the major susceptibility, with some unidentified environmental exposures believed to play a role as well.

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