Overprotective parents inhibit more than their kids' freedom: they may also slow brain growth in an area linked to mental illness.
Children whose parents are overprotective or neglectful are believed to be more susceptible to psychiatric disorders – which in turn are associated with defects in part of the prefrontal cortex.
To investigate the link, Kosuke Narita of Gunma University, Japan, scanned the brains of 50 people in their 20s and asked them to fill out a survey about their relationship with their parents during their first 16 years.
The researchers used a survey called the Parental Bonding Instrument (pdf), an internationally recognised way of measuring children's relationships with their parents. It asks participants to rate their parents on statements like "Did not want me to grow up", "tried to control everything I did" and "tried to make me feel dependent on her/him".
Narita's team found that those with overprotective parents had less grey matter in a particular area of the prefrontal cortex than those who had had healthy relationships. Neglect from fathers, though not mothers, also correlated with less grey matter.
This part of the prefrontal cortex develops during childhood, and abnormalities there are common in people with schizophrenia and other mental illnesses.
Narita and his team propose that the excessive release of the stress hormone cortisol – due either to neglect, or to too much attention – and reduced production of dopamine as a result of poor parenting leads to stunted grey matter growth.
Anthony Harris, director of the Clinical Disorders Unit at Westmead Hospital in Sydney, Australia, says the study is important for highlighting to the wider community that parenting styles can have long-term effects on children.
Parents to blame?
But he adds that such brain differences are not always permanent. "Many individuals show great resilience," he says.
Stephen Wood, who studies adolescent development at the Melbourne Neuropsychiatry Centre in Australia, says the brain abnormalities cannot necessarily be blamed on children's relationship with their parents. He points out that the subjects studied may have been born with the abnormalities and as a result didn't bond well with their parents, rather than vice versa.
Wood also takes issue with the study team's decision to exclude individuals with low socioeconomic status and uneducated parents – two factors known to contribute to poor performance in cognitive tests. "The effect they found may be real, but why worry about parenting if there are other factors that are so much larger?" he says.
Journal Reference: Progress in Neuro-Psychopharmacology and Biological Psychiatry, DOI: 10.1016/j.pnpbp.2010.02.025News by SoulRiser on March 23, 2010 @ 6:53 PM