Causes of Asperger’s Syndrome

An Autistic Disorder (autism) is one of a number of Pervasive Developmental Disorders (PDD) or in Europe known as Autistic Spectrum Disorders. Autistic Disorders are subdivided into five categories:

• Classic autism: is generally recognized by the time children are toddlers. It is the most severe of the PDDs and is marked by a significant developmental delay.
• Asperger’s syndrome: Development appears normal or even above average until problems in socialization and communication are recognized, usually between the ages of five and nine years old.
• Disintegrative disorder: Development is normal but seems to revert at an early age. 
• Rett disorder: The one disorder in the Autistic spectrum that has been defined as a rare genetic disorder caused by a defect in a single gene. In addition, unlike other forms of autism Rett disorder affects more females than males. 
• Autism spectrum disorder NOS (not otherwise specified): Those diagnosed with PDD that don’t fit into another class in the spectrum.

The cause of autistic disorders, except for Rett disorder, has yet to be clearly defined. However, ongoing research has elicited several theories about the causes of Asperger’s syndrome and other autistic disorders.

Although it is widely accepted that Autistic spectrum disorders, including Asperger’s syndrome are caused genetically, some researchers believe that genetic research too often is given priority over environmental and other types of research. Studies of twins show that if one identical twin has an autistic disorder, from 60-90 percent of the time, the other twin will as well. However, the other 10% of the time one identical twin may be autistic while the other is not. Furthermore, while some families have more than one autistic child, others may have both autistic and non-autistic children. These facts confirm only that the causes of autistic disorders are complex. Many experts believe that the symptoms of Asperger’s syndrome and other autistic disorders may not result from any single cause.

Genetic or not, several studies of the brain in autistic individuals are helping science to pinpoint the factors that lead to autistic disorders such as Asperger’s syndrome.

Underconnectivity theory

With the aid of functional magnetic resonance imaging (fMRI),  researchers at Carnegie Mellon have found numerous abnormalities in the activity of brains of autistic people with normal IQs. First findings indicated white matter abnormalities in the brain. In correlation, new findings also indicate a deficiency in coordination and synchronization of some brain areas.

A separate study conducted at Carnegie Mellon's Center for Cognitive Brain Imaging (CCBI), compared a group of autistic adults to a control group of normal participants of similar ages and IQs. The autistic group showed less activity in the anterior (front) regions of the brain and more activity in the posterior regions than the control group. Overall synchronization among the brain regions was weaker for the autistic group than for the control group. In addition, the autistic group showed more activity in the right hemisphere of the brain than the left in direct contrast to the control group.

Extreme Male Brain Theory

In general, men are better at cognitive or systematic thinking, (i.e. building from objects and facts). Women are better at empathetic or perceptual thinking (i.e. building from ideas and feelings).

The extreme male brain theory suggests that those with autistic disorders display an extreme cognitive thinking brain. Some studies have indicated that when high levels of testosterone are released during pregnancy, the baby (whether male or female) develops an extreme cognitive thinking brain that is a characteristic of Asperger’s syndrome and other autistic disorders. Simon Baron-Cohen, director of the Autism Research Centre at Cambridge University and his colleagues are investigating this theory. Baron-Cohen believes that the autistic mind over-systematizes at the expense of empathy.

Robert Schultz, director of the Yale Developmental Neuroimaging Laboratory, and his colleagues have studied a brain region called the fusiform face area. MRI studies show that this area, which normally lights up when a person sees a face, is impaired in autistic individuals. The amygdala (emotional center of the brain) appears to be less active in autistic people than in others. When an autistic person sees emotional faces, for instance, the pathways that normally are illuminated remain dark. MRI studies also indicate that in autistic people, the prefrontal cortex (believed to be the center of empathic behavior) is less active in those with autistic disorders.

Weak Central Coherence Theory

In the late 1980s, Uta Frith of University College London proposed the weak central coherence theory that autistic people think about things in the smallest possible parts. The theory explains how some autistic people are remarkably skilled in some subjects like math and engineering but deficient in communication and socialization skills. However, even Frith admits that her theory does not conclusively explain the causes of autism, but only the cognitive strength that the autistic individual displays.

Other theories address the rise of autism in recent times. One of the most controversial is that conditions such as autism and Asperger's are caused by the side-effects of vaccinations. However this theory has been widely discounted due to the fact that autistic disorders are more prevalent in males although both sexes are immunized in about the same numbers.

To a lesser extent, other environmental theories are being considered. Included are those that hypothesize that chemicals, mold, fluoridated water, and heavy metals in fish may be causes of autistic disorders. Maternal medical conditions are also being considered. These include medications like birth control pills, fertility drugs, and maternal health conditions such as hypothyroidism and viral infections during pregnancy.

No matter what the causes, PDDs are a significant problem for children, their families, and the services they need (e.g. schools). To that effect, the Centers for Disease Control and Prevention consider autistic disorders an urgent health problem that affects us all.

NOTE: This article was written by a lay person to provide you with general information about possible causes and ongoing research regarding Asperger’s syndrome and autistic disorders. For more definitive information, please follow these links:

Sources: Inside Autism, CDC (Center for Disease Control and Prevention), Carnegie Mellon Press Release 7/27/2004, Carnegie Mellon Press Release 11/29/2004

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