Childhood environment and socioeconomic status appear to affect cognitive ability and brain development during adolescence, independently of genetic factors, according to a new study by a research team at Karolinska Institutet in Sweden.
The findings, published in the journal Proceedings of the National Academy of Sciences (PNAS), demonstrate how important the family environment is, not just during early infancy but throughout all of adolescence.
While the way in which genes and environment (nature vs. nurture) affect the brain and cognitive faculties is still hotly debated, previous research has not taken genes into account while looking at the environmental effects.
The Swedish research team conducted a study in which they analyze environmental factors while also looking at a new genetic measure: an index value based on a cluster of the 5,000 or so DNA locations that are most strongly linked to educational achievements.
The study involved 551 adolescents from different socioeconomic environments in different areas in Europe. At the age of 14, the participants gave DNA samples, completed cognitive tests and had their brain imaged in an MR (magnetic resonance) scanner. The process was repeated again five years later.
At the age of 14, genes and environment were independently linked to cognitive ability (measured using working memory tests) and brain structure. However, the environmental effects were found to be 50 to 100 percent stronger than the genetic effects. Differences in socioeconomic status were associated with differences in the total surface area of the neocortex.
“The previous debate was whether there is a special area that is affected by the environment, such as long-term memory or language,” said Nicholas Judd, doctoral student at the Department of Neuroscience, Karolinska Institutet and co-first author of the study along with his departmental colleague Bruno Sauce, Ph.D.
“However, we’ve been able to show that the effect occurs across the neocortex and so probably affects a whole host of functions.”
Genetic differences were also linked to brain structure, affecting not only the brain’s total area but also specifically an area of the right parietal lobe known to be important for mathematical skills, reasoning and working memory. This is the first time a brain area has been identified that is linked to this genetic index.
When the research team followed up on the teens five years later, they were able to look at how genes and the environment had affected the brain’s development during adolescence. What they found was that while the genes did not explain any of the cerebral changes, the environment did. However, it is unknown which aspect of the environment is responsible for this.
“There are a number of possible explanations, such as chronic stress, diet or intellectual stimulation, but the study shows just how important the environment is, not only during early childhood,” said principal investigator Dr. Torkel Klingberg, professor of cognitive neuroscience at the Karolinska Institutet.
“Finding the most important environmental factors for optimising childhood and adolescent development is a matter for future research.”
The study is published in the journal Proceedings of the National Academy of Sciences (PNAS).
Source: Karolinska Institutet
Source: PsychCentral Family Environment Affects Teen Brain Development