Scientists have found that increasing the levels of a molecule in a particular part of the brain can
reduce anxious temperament in young monkeys. The finding sheds light on the origins of anxiety
disorders and how it might be possible to devise early treatments for those at risk.
Although there are some effective treatments for anxiety disorders, they do not work for
everybody. Also, in some cases, they do not treat all of the symptoms.
Researchers from the University of California (UC), Davis, the University of Wisconsin-
Madison and the State University of New York in Brooklyn worked on the new study.
The team describes the findings in a recent Biological Psychiatry paper.
An anxious temperament is a risk factor for anxiety disorders and depression. Children who are
extremely shy and nervous are more likely both to develop these conditions later in life and to
abuse of alcohol and drugs.
In earlier work with young rhesus macaques, the researchers had identified that the amygdala
forms a central part of the brain circuitry of anxious temperament.
The amygdala is a brain region that has a key role in a person's emotions.
In the new study, the team used genetic, imaging, and behavioral methods to probe the molecular
components of the anxious temperament brain circuit.
The search led them to a handful of molecules from which they selected a single one,
neurotrophin-3, to investigate further.
Neurotrophin-3 is a growth factor that promotes the production of new nerve cells and their
The researchers found that increasing the levels of neurotrophin-3 in the brains of young
monkeys reduced the animals the tendency to view situations as threatening.
There are millions of people worldwide who suffer from debilitating anxiety and depressive
disorders," says first study author Andrew S. Fox, Ph.D., an assistant professor in psychology at
These disorders are also some of the leading causes of disability and days lost to disability,
adds Fox, who also works as a researcher at the California National Primate Research Center.
Feelings of anxiety are part of day-to-day life. They can arise when making important decisions,
facing difficulties at work, or anticipating events such as tests and exams.
For people with anxiety disorders, however, the feelings do not subside, and they can even get
worse over time. For these individuals, persistent symptoms can disrupt relationships and work
or school life.
The symptoms of anxiety vary, depending on the specific disorder.
People with generalized anxiety disorder find themselves continually on edge, restless, irritable,
tired, worried, tense, and unable to concentrate. They may also experience sleep difficulties.
For people with panic disorder, it is not only the attacks themselves but also the anticipation and
worry about the next one that can disrupt daily life.
Panic attacks can be sudden and bring on intense fear, causing heart palpitations, trembling,
sweating, and shaking. Sensations of choking and smothering, as well as a feeling of losing
control, can also accompany these symptoms.
People with phobia-related anxiety have an intense aversion or fear of specific objects or
situations that are out of proportion to the danger that they pose. The worry and the steps that
people take to avoid their phobia triggers can seriously interfere with their everyday activities.
A World Health Organization (WHO) estimate from 2015 suggests that the number of people
worldwide living with anxiety disorders totals 264 million.
In the United States, anxiety disorders affect about 40 million adults, according to the Anxiety
and Depression Association of America.
Using a modified virus, Fox and colleagues increased levels of neurotrophin-3 in the dorsal
the amygdala of preadolescent rhesus macaques.
Raising neurotrophin-3 in this brain region led to a reduction in anxiety-related behaviors,
including those relating to inhibition, which is a known early risk factor for anxiety disorders.
Brain scans revealed that increasing neurotrophin-3 in the dorsal amygdala altered activity in all
of the brain regions that play a role in anxiety.
The researchers have also listed other molecules that they consider worthy of further study in
relation to anxiety and associated conditions.
Fox believes that the recent study has identified what could be the first of many molecules with a
causal role in the development of anxiety in nonhuman primates. We’re only just beginning.
There could be hundreds or even thousands more.
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