This 2015 Wisconsin macaque study was another attempt to justify the school’s continuing captivity of thousands of monkeys. The researchers performed a study that, if its experimental design was truly informative for helping humans, could have been done with humans.
A problem I saw in the news coverage was that the finding of:
“35 percent of variation in anxiety-like tendencies is explained by family history”
was attributed to genetics, with headlines such as “Anxious Brains Are Inherited, Study Finds.” The lead researcher encouraged this misinterpretation with statements such as:
“Over-activity of these three brain regions are inherited brain alterations that are directly linked to the later life risk to develop anxiety and depression.”
However, the researchers produced this finding by running numbers on family trees, not by studying genetic samples to assess the contributions of genetic and epigenetic factors. The study’s “family history” correlation was therefore different than finding an inherited genetic causation that wasn’t influenced by the subjects’ caged environments.
The study found:
“Metabolism within a tripartite prefrontal-limbic-midbrain circuit mediates some of the inborn risk for developing anxiety and depression.
The brain circuit that was genetically correlated with individual differences in early-life anxiety involved three survival-related brain regions. These regions were located in the brain stem, the most primitive part of the brain; the amygdala, the limbic brain fear center; and the prefrontal cortex, which is responsible for higher-level reasoning and is fully developed only in humans and their primate cousins.”
The 592 subjects were the human-equivalent ages of 3 to 12 years old. Primate brainstems and limbic systems are fully developed before these ages.
The researchers thus skipped over potential evidence for the important contributions of epigenetic factors to “the later life risk to develop anxiety and depression” that change the studied brain areas during womb-life, infancy, and early childhood. Studies such as:
- Epigenetic changes in the developing brain change behavior
- Stress in early life can alter physiology and behavior across the entire lifespan
show, for example, that:
- A developing fetus adapts to being constantly stressed by an anxious mother.
- When these adaptations persist after birth, they may present as physiological and behavioral maladaptations of the infant and young child to a non-stressful environment.
- Later in life, these enduring changes may be among the causes of symptoms
such as the anxious overreactions this study found.
http://www.pnas.org/content/112/29/9118.full “Intergenerational neural mediators of early-life anxious temperament”