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(Reuters Health) – – Beyond the well-known effects of lead exposure in children on IQ, a new study suggests that lasting effects on the brain could extend to personality traits at adulthood.
Of the more than 500 New Zealanders whose blood lead levels were tested as children, those with higher concentrations in children were more likely to have personality traits related to a number of negative consequences on their lives, including greater psychopathology, poorer physical health, less job satisfaction and difficult interpersonal relationships.
"We were following people born decades ago when lead was still very much in our atmosphere," said Aaron Reuben, PhD candidate in clinical psychology at Duke University in Durham, North Carolina. "We asked the following question: if a person was exposed to lead as a child, would it affect him in adulthood in terms of mental health and personality?"
Although the effects noted by Reuben's team were "modest", they were comparable to the results of previous studies of these same New Zealanders, including a slight decline in IQ and a slightly higher risk of criminal behavior. he declared. In addition, the impact of lead has been shown to be comparable to that of other modifiable risk factors, such as child abuse.
Peak concentrations of lead in the air coincided with its use in gasoline between the 1940s and the early 1990s, writes the Reuben team in JAMA Psychiatry. They note that from 1976 to 1980, the average child in the United States had blood lead levels three times higher than the current standard of clinical attention.
The researchers badyzed data from a large multigenerational health study of 579 people born in 1972 and 1973 in Dunedin, New Zealand. Participants had their blood tested for lead at age 11 and were interviewed every two to six years in adulthood for indicators of mental disorders. They were also asked to identify people who knew them well to describe them with the help of a 25 item questionnaire measuring five personality traits: neuroticism, extroversion, openness to experience, friendliness and conscience.
The results showed that people with higher levels of lead in children "were a little more neurotic, a little less pleasant, a little less conscientious," said Reuben. "And these factors influence your professional performance and interpersonal relationships."
Each increase of 5 micrograms per deciliter of blood lead to 11 years was badociated with a 34% increase in adult age of the likelihood of general psychopathological symptoms such as thought disorders, and slight increases in neurotism as well as that's a decrease in agility and consciousness. , the study found.
These badociations can not prove the cause and effect, but the researchers were able to take into account various factors that could influence the results. For example, they show that the socio-economic status of childhood was not related to the psychiatric traits of the adult.
While other studies have examined the effects of lead exposure on the risk of future antisocial behavior, ADHD and IQ, "these researchers examined personality traits," said Joel Nigg, Professor of Psychiatry, Pediatrics and Behavioral Neuroscience at Oregon Health and Science University in Portland. "It's a nice extension."
It's important to note "that these were fairly high blood lead levels compared to what you see today," said Nigg, who did not participate in the new study. "They are about 10 times higher than those you see in American children today."
Nevertheless, said Nigg, "many studies show that much lower levels of lead are linked to children's mental health problems. Although we do not have longitudinal data, the short-term data show the same types of effects (as reported in the new study) at low levels of lead. "
Nigg's own research has shown that genetics can play a role in the impact of lead exposure. "The effect of lead on development can be very different depending on the genetic makeup of each," he said.
This means that the effects measured in a study such as Reuben 's might be more important for some children and smaller for others than the reported average, said Nigg. "Our study showed that some children were very sensitive to ADHD."
SOURCE: bit.ly/2HtR3hl JAMA Psychiatry, online 23 January 2019.
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