Lead exposure during childhood may influence mental health in adulthood, a new study suggests.
Lead is a type of metal that people throughout the world have used in the construction of water pipes, added into paint to prevent corrosion, and put into gasoline to maintain engine durability.
However, over the years, researchers have concluded that lead is toxic and can be extremely dangerous.
According to the World Health Organization (WHO), "there is no known level of lead exposure that is considered safe." In time, ingested lead particles tend to accumulate in a person's bones, brain, and other organs, increasing the risk of health problems, including high blood pressure, and damage to the kidneys.
Now, new research from Duke University in Durham, NC, also suggests that exposure to lead during childhood can affect how an individual's personality develops and predispose them to mental health problems in adulthood.
The research findings, which appear in JAMA Psychiatry, indicate that people who had high levels of lead in their blood when they were young are more likely to experience mental health issues by the time they turn 38. The study also indicates that they are also more likely to have developed unhealthy personality traits, such as neuroticism.
'High lead levels were viewed as normal'
The research team looked at the data of 1,037 participants, all born in born in 1972 and 1973 in Dunedin, New Zealand. Then, New Zealand was one of the countries who added the highest levels of lead to gasoline.
Of the total number of participants, 579 children received blood tests to measure their level of exposure to lead when they were 11 years old. The results showed that 94 percent of these children had lead levels higher than 5 micrograms per deciliter of blood (ug/dL).
Nowadays, when a child has blood lead levels of 5 (ug/dL), they will immediately receive a referral for special medical attention. However, this did not use to be the case decades ago.
"These are historical data from an era when lead levels like these were viewed as normal in children and not dangerous, so most of our study participants were never given any treatment for lead toxicity," says the study's senior author, Terrie Moffitt.
Throughout the study, the participants also took part in regular mental health assessments, with the most recent assessment taking place when the volunteers were 38 years old.
The researchers assessed the participants' psychopathology factor (p-factor), which is a mental health measurement. They determined the factors by looking at 11 disorders: alcohol misuse, dependence on cannabis, tobacco, and hard drugs, conduct disorder, major depression, generalized anxiety disorder, phobias, obsessive-compulsive disorder, mania, and schizophrenia.
After looking at the p-factor in conjunction with blood lead levels, the researchers concluded that, while lead exposure's impact on mental health may be modest, it may have far-reaching effects.
Lead exposure's "effects really can last for quite a long time, in this case, 3 to 4 decades," according to study coauthor Jonathan Schaefer.
"Lead exposure decades ago may be harming the mental health of people today who are in their 40s and 50s," Schaefer warns.
Effect on personality?
Besides upping the mental health risk, it appears that lead exposure during childhood also affects individuals' adult personalities.
When quizzing friends and family members about the participants' personalities, the researchers found that the ones with evidence of the highest lead exposure seemed to present more neurotic tendencies, were less agreeable, and less conscientious compared with participants with lower lead exposure in childhood.
The researchers note that having unhealthier personality traits can affect a person's adaptability to different life situations, impacting their relationships and levels of job satisfaction. Negative personality traits, the investigators add, are also associated with poorer mental health, overall.
"For folks who are interested in intervention and prevention, the study suggests that if you're going to intervene on a group of kids or young adults that have been lead exposed, you may need to think very long-term when it comes to their care," Schaefer explains.
Moreover, although the current study focused specifically on a population from New Zealand, the investigators emphasize that their findings could be relevant across cohorts since many countries across the globe used leaded gasoline in the past.
"When we see changes that may be the result of lead exposures in New Zealand, it's very likely that you would have seen those same impacts in America, in Europe, and the other countries that were using leaded gasoline at the same levels at the same time."
Study coauthor Aaron Reuben
The research team would also like to find out whether lead exposure in childhood could also influence the development of neurodegenerative diseases, such as dementia, and the development of cardiovascular problems.