In the United States, we've seen a fifteen-fold increase in autism diagnoses over the past two decades. In fact, it's currently estimated that almost 1% of US children have an autism-spectrum disorder (ASD), while the rates in US adults are largely unknown. Autism is described in the DSM-IV, listed as a disorder usually first diagnosed in infancy, childhood, or adolescence. Autism is further categorized as a pervasive developmental disorder, falling within the autistism spectrum, along with Asperger's and PDD-NOS.
Autism is characterized by impaired social development, limited communication skills, and repetitive movements. Autistic individuals may have dysfunctional mirror neuron systems, which are involved in imitation learning and empathy. The mirror neuron system is thought of as the neural basis for human social cognition, and anatomical studies show a significant reduction in cortical mass of brain areas directly populated by mirror neurons in individuals with autism.
The causes of autism, however, remain unclear. Genetic factors, dysfunctional cell-to-cell communication, and even environmental factors such as teratogens (chemicals that cause birth defects) have all been implicated. Indeed, ASDs may be as unique as the people who live with them, and a one-size-fits-all explanation may never be sufficient. One thing we know for certain is that there has never been a legitimate link found between autism and vaccine use. The science simply does not support childhood vaccination as a causal factor.
In a special issue of Discover Magazine released earlier this year, five intriguing yet largely speculative causes of the disorder are discussed. From an autoimmune hypothesis to a model of impaired mitochondria, these provocative explanations challenge conventional wisdom, and may, in fact, open the door to a new way of thinking about ASDs. We have learned a lot about autism recently, and with each new discovery, the picture grows clearer.
Both children and adults with ASDs appear to have difficulty connecting social cues with a personal emotional experience. Interestingly, they are largely immune to the highly "contagious" yawn. In a study performed on yawning behaviors in young children, only 11% of autistic children aged five to twelve-years-old caught yawns, as opposed to 43% of matched controls.
In multiple clinical studies, oxytocin, the hormone implicated in human bonding, has been shown to improve social skills in adults with ASDs. Compared to placebo, autistic adults taking oxytocin demonstrated an increased ability to understand emotional speech, improved identification of cooperation in a simulated social setting, and even a reduction in repetitive behaviors. This is an exciting development, since there is currently no known medical treatment for social or communication problems, aside from intensive behavioral intervention.
Last year, a study published in the Journal of Neuroscience provided convincing evidence that one of the first signs of autism is excessive brain growth. Although children are usually diagnosed between the ages of three and four, secondary to behavioral problems and delays, it is notable that autistic children have measurably larger brains within the first year of life. Although no cure for autism exists, earlier screening tools may lead to earlier behavioral interventions.
Autism is four times more prevalent in boys than in girls, and until recently, researchers could only speculate as to a genetic or hormonal cause for the discrepancy. But, in a study released earlier this year, a gene-hormone interaction that appears to be largely implicated was identified. Retinoic acid-related orphan receptor-alpha (RORA) is a gene that indirectly controls production of sex hormones via an enzyme called aromatase. In the brains of individuals with autism, the way these neurochemicals communicate seems to be dysregulated, causing lower than normal levels of RORA proteins and aromatase, and a significant buildup of testosterone. This could explain why boys are so much more commonly affected than girls, since high levels of estrogen appear to protect against dysfunction of this system.
Another recent trend I've noticed in the scientific literature is one that celebrates the unique perspective, focus, and creativity seen in the autistic community, instead of fixating on deficits alone. The human side of autism is beautifully displayed in a recent issue of National Geographic, wherein photographer Timothy Archibald presents "Echolilia," an expose of his child's autism, and a joint effort between father and son to learn more about the minds of one another, minds that often feel frustratingly inaccessible. In addition, a New York Times article published just this week tells the romantic story of Jack and Kristen, two young people who love one another in spite of, or perhaps by virtue of, the daily autistic experience. Stories like these remind us that the science and humanity of autism are inextricably linked, and we cannot know one without knowing the other.