On Monday, September 16, 2013, a gunman killed 12 people as the workday began at the Washington
Navy Yard in Washington, DC. Aaron Alexis, 34, had a troubled history: he thought that he was being
controlled by radio waves. He called the police to complain about voices in his head and being under
surveillance by “shadowy forces” (Thomas, Levine, Date, & Cloherty, 2013). While Alexis’s actions
cannot be excused, it is clear that he had some form of mental illness. Mental illness is not necessarily a
cause of violence; it is far more likely that the mentally ill will be victims rather than perpetrators of
violence (Stuart, 2003). If, however, Alexis had received the help he needed, this tragedy might have
been averted.
Clive Wearing is an accomplished musician who lost his ability to form new memories when he became
sick at the age of 46. While he can remember how to play the piano perfectly, he cannot remember
what he ate for breakfast just an hour ago (Sacks, 2007). James Wannerton experiences a taste
sensation that is associated with the sound of words. His former girlfriend’s name tastes like rhubarb
(Mundasad, 2013). John Nash is a brilliant mathematician and Nobel Prize winner. However, while he
was a professor at MIT, he would tell people that the New York Times contained coded messages from
extraterrestrial beings that were intended for him. He also began to hear voices and became suspicious
of the people around him. Soon thereafter, Nash was diagnosed with schizophrenia and admitted to a
state-run mental institution (O’Connor & Robertson, 2002). Nash was the subject of the 2001 movie A
Beautiful Mind. Why did these people have these experiences? How does the human brain work and
what happens when the brain and behavior go awry?
Video: Psychological Disorders
https://youtu.be/wuhJ-GkRRQc
Video: OCD and Anxiety Disorders
https://youtu.be/aX7jnVXXG5o
Video: Trauma and Addiction
https://youtu.be/343ORgL3kIc
Video: Depressive and Bipolar Disorders
https://youtu.be/ZwMlHkWKDwM
Video: Schizophrenia and Dissociative Disorders
https://youtu.be/uxktavpRdzU
Video: Personality Disorders
https://youtu.be/4E1JiDFxFGk
Causes of Autism Spectrum Disorder
Neurodevelopmental disorders are a group of disorders that are typically
diagnosed during childhood and are characterized by developmental deficits in
personal, social, academic, and intellectual realms; these disorders include
attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorder.
ADHD is characterized by a pervasive pattern of inattention and/or hyperactive
and impulsive behavior that interferes with normal functioning. Genetic and
neurobiological factors contribute to the development of ADHD, which can persist
well into adulthood and is often associated with poor long-term outcomes.
The major features of autism spectrum disorder include deficits in social
interaction and communication and repetitive movements or interests. As with
ADHD, genetic factors appear to play a prominent role in the development of
autism spectrum disorder; exposure to environmental pollutants such as mercury
have also been linked to the development of this disorder. Although it is believed
by some that autism is triggered by the MMR vaccination, the evidence does not
support this claim.
Early theories of autism placed the blame squarely on the shoulders of the child’s
parents, particularly the mother. Bruno Bettelheim (an Austrian-born American
child psychologist who was heavily influenced by Sigmund Freud’s ideas)
suggested that a mother’s ambivalent attitudes and her frozen and rigid emotions
toward her child were the main causal factors in childhood autism.
In what must certainly stand as one of the more controversial assertions in
psychology over the last 50 years, he wrote, “I state my belief that the
precipitating factor in infantile autism is the parent’s wish that his child should
not exist” (Bettelheim, 1967, p. 125). As you might imagine, Bettelheim did not
endear himself to a lot of people with this position; incidentally, no scientific
evidence exists supporting his claims.
The exact causes of autism spectrum disorder remain unknown despite massive
research efforts over the last two decades (Meek, Lemery-Chalfant, Jahromi, and
Valiente, 2013). Autism appears to be strongly influenced by genetics, as identical
twins show concordance rates of 60%–90%, whereas concordance rates for
fraternal twins and siblings are 5%–10% (Autism Genome Project Consortium,
2007). Many different genes and gene mutations have been implicated in autism
(Meek et al., 2013). Among the genes involved are those important in the
formation of synaptic circuits that facilitate communication between different
areas of the brain (Gauthier et al., 2011).
A number of environmental factors are also thought to be associated with
increased risk for autism spectrum disorder, at least in part, because they
contribute to new mutations. These factors include exposure to pollutants, such
as plant emissions and mercury, urban versus rural residence, and vitamin D
deficiency (Kinney, Barch, Chayka, Napoleon, and Munir, 2009).
Child Vaccinations and Autism Spectrum Disorder
In the late 1990s, a prestigious medical journal published an article purportedly
showing that autism is triggered by the MMR (measles, mumps, and rubella)
vaccine. These findings were very controversial and drew a great deal of
attention, sparking an international forum on whether children should be
vaccinated. In a shocking turn of events, some years later the article was retracted
by the journal that had published it after accusations of fraud on the part of the
lead researcher. Despite the retraction, the reporting in popular media led to
concerns about a possible link between vaccines and autism persisting.
A recent survey of parents, for example, found that roughly a third of respondents
expressed such a concern (Kennedy, LaVail, Nowak, Basket, and Landry, 2011);
and perhaps fearing that their children would develop autism, more than 10% of
parents of young children refuse or delay vaccinations (Dempsey et al., 2011).
Some parents of children with autism mounted a campaign against scientists who
refuted the vaccine-autism link. Even politicians and several well-known
celebrities weighed in; for example, actress Jenny McCarthy (who believed that a
vaccination caused her son’s autism) co-authored a book on the matter. However,
there is no scientific evidence that a link exists between autism and vaccinations
(Hughes, 2007).
Indeed, a recent study compared the vaccination histories of 256 children with
autism spectrum disorder with that of 752 control children across three time
periods during their first two years of life (birth to 3 months, birth to 7 months,
and birth to 2 years) (DeStefano, Price, and Weintraub, 2013). At the time of the
study, the children were between 6 and 13 years old, and their prior vaccination
records were obtained. Because vaccines contain immunogens (substances that
fight infections), the investigators examined medical records to see how many
immunogens children received to determine if those children who received more
immunogens were at greater risk for developing autism spectrum disorder.
The results of this study, a portion of which is shown in the figure, clearly
demonstrate that the quantity of immunogens from vaccines received during the
first two years of life was not at all related to the development of autism
spectrum disorder. There is not a relationship between vaccinations and autism
spectrum disorders.
A graph has an x-axis labeled “total cumulative immunogens” and a y-axis with
percentage numbers. For children aged 0–3 months, the data is approximately as
follows: 0–25 immunogens are about 48% for ASD cases and 41% for controls, 26–
50 immunogens are 5% for ASD cases and 6% for controls, and for 3000–3258
immunogens45% for ASD cases and 50% for controls. For children aged 0–
7months, the data is approximately as follows: 26–50 immunogens are about 20%
for ASD cases and 18% for controls, 51–75 immunogens are 25% for ASD cases
and 22% for controls, 3000–3258 immunogens are 45% for ASD cases and 52% for
controls, 6000–6258 immunogens are 10% for ASD cases and 8% for controls, and
for 9000–9258 immunogens 33% for ASD cases and 40% for controls. For children
aged 0–24 months, the data is approximately as follows: 151–175 immunogens
are about 25% for ASD cases and 25% for controls, 176–200 immunogens are 18%
for ASD cases and 13% for controls, 9000–9528 immunogens are 17% for ASD
cases and 20% for controls, and for 12000–12258 immunogens 25% for ASD cases
and25% for controls.
Figure: In terms of their exposure to immunogens in vaccines, overall, there is not
a significant difference between children
with autism spectrum disorder and their age-matched controls without the
disorder (DeStefano et al., 2013).
Why does concern over vaccines and autism spectrum disorder persist? Since the
proliferation of the Internet in the 1990s, parents have been constantly
bombarded with online information that can become magnified and take on a life
of its own. The enormous volume of electronic information pertaining to autism
spectrum disorder, combined with how difficult it can be to grasp complex
scientific concepts, can make separating good research from bad challenging
(Downs, 2008).
Notably, the study that fueled the controversy reported that 8 out of 12
children—according to their parents—developed symptoms consistent with
autism spectrum disorder shortly after receiving a vaccination. To conclude that
vaccines cause autism spectrum disorder on this basis, as many did, is clearly
incorrect for a number of reasons, not the least of which is because correlation
does not imply causation, as you’ve learned.
Additionally, as was the case with diet and ADHD in the 1970s, the notion that
autism spectrum disorder is caused by vaccinations is appealing to some because
it provides a simple explanation for this condition. Like all disorders, however,
there are no simple explanations for autism spectrum disorder. Although the
research discussed above has shed some light on its causes, science is still a long
way from the complete understanding of the disorder.
Licenses and Attributions
Psychology. Authored by: OpenStax College. Located at:
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References: https://cnx.org/contents/Sr8Ev5Og@5.73:LMdT4sx_@5/Introduction
Causes of ADHD
Neurodevelopmental disorders are a group of disorders that are
typically diagnosed during childhood and are characterized by
developmental deficits in personal, social, academic, and intellectual
realms; these disorders include attention deficit/hyperactivity disorder
(ADHD) and autism spectrum disorder.
ADHD is characterized by a pervasive pattern of inattention and/or
hyperactive and impulsive behavior that interferes with normal
functioning. Genetic and neurobiological factors contribute to the
development of ADHD, which can persist well into adulthood and is
often associated with poor long-term outcomes.
Family and twin studies indicate that genetics play a significant role in
the development of ADHD. Burt (2009), in a review of 26 studies,
reported that the median rate of concordance for identical twins was
.66 (one study reported a rate of .90), whereas the median
concordance rate for fraternal twins was .20.
This study also found that the median concordance rate for unrelated
(adoptive) siblings was .09; although this number is small, it is greater
than 0, thus suggesting that the environment may have at least some
influence. Another review of studies concluded that the heritability of
inattention and hyperactivity were 71% and 73%, respectively (Nikolas
and Burt, 2010).
The specific genes involved in ADHD are thought to include at least two
that are important in the regulation of the neurotransmitter dopamine
(Gizer, Ficks, and Waldman, 2009), suggesting that dopamine may be
important in ADHD. Indeed, medications used in the treatment of
ADHD, such as methylphenidate (Ritalin) and amphetamine with
dextroamphetamine (Adderall), have stimulant qualities and elevate
dopamine activity.
People with ADHD show less dopamine activity in key regions of the
brain, especially those associated with motivation and reward (Volkow
et al., 2009), which provides support to the theory that dopamine
deficits may be a vital factor in the development this disorder (Swanson
et al., 2007).
Brain imaging studies have shown that children with ADHD exhibit
abnormalities in their frontal lobes, an area in which dopamine is in
abundance. Compared to children without ADHD, those with ADHD
appear to have smaller frontal lobe volume, and they show less frontal
lobe activation when performing mental tasks. Recall that one of the
functions of the frontal lobes is to inhibit our behavior. Thus,
abnormalities in this region may go a long way toward explaining the
hyperactive, uncontrolled behavior of ADHD.
By the 1970s, many had become aware of the connection between
nutritional factors and childhood behavior. At the time, much of the
public believed that hyperactivity was caused by sugar and food
additives, such as artificial coloring and flavoring. Undoubtedly, part of
the appeal of this hypothesis was that it provided a simple explanation
of (and treatment for) behavioral problems in children.
A statistical review of 16 studies, however, concluded that sugar
consumption has no effect at all on the behavioral and cognitive
performance of children (Wolraich, Wilson, and White, 1995).
Additionally, although food additives have been shown to increase
hyperactivity in non-ADHD children, the effect is rather small (McCann
et al., 2007). Numerous studies, however, have shown a significant
relationship between exposure to nicotine in cigarette smoke during
the prenatal period and ADHD (Linnet et al., 2003). Maternal smoking
during pregnancy is associated with the development of more severe
symptoms of the disorder (Thakur et al., 2013).
Is ADHD caused by poor parenting? Not likely. Remember, the genetics
studies discussed above suggested that the family environment does
not seem to play much of a role in the development of this disorder; if
it did, we would expect the concordance rates to be higher for fraternal
twins and adoptive siblings than has been demonstrated. All things
considered, the evidence seems to point to the conclusion that ADHD is
triggered more by genetic and neurological factors and less by social or
environmental ones.
Why is the Prevalence Rate of ADHD Increasing?
Many people believe that the rates of ADHD have increased in recent
years, and there is evidence to support this contention. In a recent
study, investigators found that the parent-reported prevalence of
ADHD among children (4–17 years old) in the United States increased
by 22% during a 4-year period, from 7.8% in 2003 to 9.5% in 2007 (CDC,
2010). Over time this increase in parent-reported ADHD was observed
in all sociodemographic groups and was reflected by substantial
increases in 12 states (Indiana, North Carolina, and Colorado were the
top three).
The increases were greatest for older teens (ages 15–17), multiracial
and Hispanic children, and children with a primary language other than
English. Another investigation found that from 1998–2000 through
2007–2009 the parent-reported prevalence of ADHD increased among
U.S. children between the ages of 5–17 years old, from 6.9% to 9.0%
(Akinbami, Liu, Pastor, and Reuben, 2011).
A major weakness of both studies was that children were not actually
given a formal diagnosis. Instead, parents were simply asked whether
or not a doctor or other health-care provider had ever told them their
child had ADHD; the reported prevalence rates thus may have been
affected by the accuracy of parental memory. Nevertheless, the
findings from these studies raise important questions concerning what
appears to be a demonstrable rise in the prevalence of ADHD.
Although the reasons underlying this apparent increase in the rates of
ADHD over time are poorly understood and, at best, speculative,
several explanations are viable:
ADHD may be over-diagnosed by doctors who are too quick to
medicate children as a behavior treatment.
There is greater awareness of ADHD now than in the past. Nearly
everyone has heard of ADHD, and most parents and teachers are aware
of its key symptoms. Thus, parents may be quick to take their children
to a doctor if they believe their child possesses these symptoms, or
teachers may be more likely now than in the past to notice the
symptoms and refer the child for evaluation.
The use of computers, video games, iPhones, and other electronic
devices has become pervasive among children in the early 21st century,
and these devices could potentially shorten children’s attentions spans.
Thus, what might seem like inattention to some parents and teachers
could simply reflect exposure to too much technology.
ADHD diagnostic criteria have changed over time.
Licenses and Attributions
Psychology. Authored by: OpenStax College. Located at:
http://cnx.org/contents/4abf04bf-93a0-45c3-9cbc2cefd46e68cc@4.100:1/Psychology. License: CC BY: Attribution. License
Terms: Download for free at http://cnx.org/content/col11629/latest/.
References:
https://cnx.org/contents/Sr8Ev5Og@5.73:LMdT4sx_@5/Introduction
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