Why delayed onset of mental illness? Genes impact suspect brain areas late

Summary

This script discusses the role of twins in understanding the interplay of genetics and environment, emphasizing the importance of considering age in gene-environment interactions. It highlights a longitudinal study tracking brain development and heritability in twins, revealing that brain regions' heritability changes with age, aligning with the onset of adolescent mental illnesses. The study suggests that genetic expressions during adolescence may explain the timing of illness emergence.

Takeaways

• 👶 Twins are valuable for studying nature/nurture because identical twins share almost 100% DNA, while fraternal twins share about 50%.
• 🧬 The interplay between genes (nature) and environment (nurture) is crucial, often termed GxE interactions.
• 📈 A third component, age, significantly influences how genes express themselves in different environments.
• 🧠 Brain regions' heritability changes over developmental stages, with some areas becoming more heritable during adolescence.
• 📉 The study followed approximately 800 individuals at two-year intervals to observe changes in brain, behavior, cognition, and emotions.
• 🔴 The research identified that certain brain areas become more heritable at different life stages, particularly in late adolescence.
• 🧬 The same brain areas that are most heritable during adolescence are also the regions that evolved most recently in humans.
• 🌐 These brain areas' changes in heritability correlate with the onset of mental illnesses like schizophrenia, often occurring in late adolescence.
• 🧪 The study suggests that the manifestation of genetic illnesses might be linked to when certain genes are expressed during development.
• 🔍 Future research will focus on linking the onset of mental illnesses during adolescence with typical brain changes possibly driven by the same genes.

Q & A

What is the primary purpose of studying twins in nature/nurture debates?

Studying twins helps to understand the influence of genetics (nature) versus environmental factors (nurture) on behavior and brain development. Identical twins share almost 100% of their DNA, while fraternal twins share about 50%, allowing researchers to compare similarities and differences to gauge the impact of DNA.

What is the significance of the term 'G by E interactions' mentioned in the script?

The term 'G by E interactions' refers to the interaction between genes (G) and environment (E). It highlights that both genetic and environmental factors are crucial, and their interplay is key to understanding human development and behavior.

Why is age considered a third component in the G by E interactions?

Age is considered a third component because the effect of a particular gene can vary depending on the developmental stage of an individual. Understanding where an individual is in their development is crucial to comprehend how genes and environment interact at different life stages.

How does the study track the development of individuals over time?

The study tracks development by following approximately eight hundred individuals at two-year intervals. Participants visit the NIH where they undergo brain scans and assessments of their school performance, life circumstances, behavior, emotions, and cognition.

What does the term 'heritable' mean in the context of the script?

In the context of the script, 'heritable' refers to the degree to which a particular trait, such as brain structure or function, is influenced by genetic factors and can be passed down through generations.

How do heritability patterns change as individuals develop from babies to adults?

The heritability of different brain areas changes significantly as individuals develop. Some parts of the brain become more heritable during adolescence, while others are more heritable in early childhood or middle age.

What is the significance of the brain areas that become more heritable during adolescence?

The brain areas that become more heritable during adolescence are significant because they are the parts of the brain that have evolved most recently and are involved in illnesses that often emerge during this period, such as schizophrenia.

Why is the timing of mental illnesses like schizophrenia a mystery in psychiatry?

The mystery lies in the fact that individuals are born with the genetic risks for illnesses like schizophrenia, yet the illness often does not manifest until late adolescence or early adulthood, despite the presence of the genes from birth.

How might the increased heritability of certain brain areas during adolescence relate to the onset of mental illnesses?

The increased heritability of certain brain areas during adolescence might be due to the expression of genes at that time. If these genes are not expressed earlier, it wouldn't matter if one is identical or fraternal twins because those genes are inactive. But when they become expressed, possibly due to puberty or other factors, the brain areas become more heritable and if this process goes awry, it could lead to the onset of mental illnesses.

What percentage of mental illnesses typically manifest during adolescence?

Over fifty percent of mental illnesses occur during the adolescent period.

What is the next step for researchers after identifying the link between brain changes and the onset of mental illnesses during adolescence?

The next step is to explore the link between the onset of mental illnesses during adolescence and the typical brain changes that may be driven by the same underlying genes, considering how gene expression can vary with age.