I recently learned from a fellow blogger about the Dunedin Study, which explored the issue of nature vs. nurture and turned up some fascinating results.
The study followed a group of 1000 individuals born in 1972 in the New Zealand city of Dunedin. Interviewing and testing with these individuals still continues, and the study has generated an enormous amount of data and many, many published research papers. Predict My Future – The Science of Us is a 4-episode docuseries that examines some of the findings of the study.
Some dirt is good for you
One of the topics studied was the hygiene hypothesis, which is essentially the idea that exposure to a little dirt is good for your immune (go five second rule!). Researchers found that kids who were raised in dirtier environments had more adaptive immune systems and fewer allergies. This dirtiness could come from something like having pets, or living on a farm. So put down the disinfecting wipes, and send the kids outside to roll around on the ground with the dog!
One of the tests done on the study participants was retinal imaging. The idea was to examine whether there was any connection between the venules (small veins) of the retina and cardiovascular health. They found that people with schizophrenia had dilated venules, which suggests a vascular component to the development of schizophrenia. This may turn out to be a way to determine early on who is likely to develop schizophrenia.
Another interesting piece of information that came out of the study is that among children (pre-teen) who reported hearing voices and seeing things that weren’t there, fully half went on to develop schizophrenia.
The effects of poverty
The study showed that growing up in poverty increases future health problems. Economic disparities are among the recognized social determinants of health, but what’s really interesting is that this effect persists even when people go on to become affluent as adults. This appears to be a result of increased inflammation due to childhood stressors that establishes a lifelong pattern of susceptibility.
Influences on adult outcomes
The researchers identified five personality types that were established by age five and persisted into adulthood. These were: well-adjusted (40%, flexible), reserved (15%), inhibited, under-controlled, and confident. Well-adjusted types showed psychological flexibility, and represented 40% of the sample. Well-adjusted, reserved, and confident types tended to function quite well.
Those who were inhibited (high-strung, closed to new experiences) and under-controlled (poor self-control, angry acting out, antisocial behaviours) tended to have more negative outcomes, including health problems and poor quality of life.
There were a number of childhood factors that impacted adult functioning. The amount of tv watched as a child impacted future school completion and employment. Self-control at age 4 was a strong predictor of future employment and income, as well as obesity, heart disease, sexually transmitted infections, and addictions.
Nature vs. Nurture
In an interesting interplay between nature and nurture, a certain genetic variant in the MAOA gene was associated with violent behaviour, but only when it occurred in conjunction with a traumatic childhood.
I think it’s so fascinating how much can be predicted about our adult lives based on what happened in childhood, and the findings of this study fit together well with the results of the adverse childhood experiences study on the effects of childhood trauma.
Last year I became a participant in phase 3 of the Nurses Health Study, which follows a large cohort to try to establish links between various factors. It’s so valuable that these sorts of studies are generating large amounts of data and likely some very interesting conclusions as well.
Science is a wonderful thing.
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