Science/Tech

Aggressive, Impulsive Behavior Linked To Lack Of Serotonin Receptors During Brain Development

Aggression May Be Explained By Early Brain Development
With implications for childhood psychiatry and criminal law, lacking serotonin receptors during early brain development could explain aggression and impulsive behaviors. Shutterstock

Some variations to the serotonergic system during early brain development may lead the nascent mind to more aggressive behaviors and impulsivity, explaining — though not excusing — delinquency and later criminality.

In presenting new findings to the Society for Neuroscience, lead investigators reported the development of aggression and impulsivity among laboratory mice whose receptors for serotonin had been disrupted. Upon reintroduction of those receptors, impulsivity as a trait receded while aggression remained for the long term.

Such “deviant” behavior in the animal model brings implications for how humans assess moral and legal judgment against one another, according to Nita Farahany, an academic from Duke University trained in neuroscience and law. As some criminal defendants begin to leverage neuroscience in the courtroom, the U.S. legal system continues to reassess the interplay between science and morality in human relations.

Weaker control of the prefrontal cortex, the brain’s “decider-in-chief,” may at least partially explain the lack of self-control observed in people with anti-social tendencies. Neuroscientist B.J. Casey, of Weill Cornell Medical College, says new research would soon lead to practical treatments for maladaptive behaviors, in children and adults.

"Our deeper understanding of the origins of delinquent behavior can be a double-edged sword," Casey said. "While we're making tremendous gains in neuroscience that should lead to improved treatments, our biological insights also have implications for criminal cases and the judicial process that we need to understand."

But the research on serotonergic influence of early brain development may also influence how society manages behavior in children deemed delinquent or deviant, or those merely boisterous and troublesome, who are often diagnosed with Attention Deficit Hyperactivity Disorder (ADHD). Such diagnoses in children rose 66 percent from 2000 to 2010, to more than 10.1 million cases, Northwestern University investigators reported last year in the journal Academic Pediatrics.

“ADHD is now a common diagnosis among children and teens,” study leader Craig Garfield in a news release at the time. “The magnitude and speed of this shift in one decade is likely due to an increased awareness of ADHD, which may have caused more physicians to recognize symptoms and diagnose the disorder.”

Despite some protestation over possible over-diagnosis and unwarranted drugging of American children, many investigators express enthusiasm for medical interventions — to the point of decrying a “racial imbalance” in treatment. Investigators from Pennsylvania State University and the University of California, Irvine in April found that nonwhite children were much less likely to receive diagnoses for the disorder. On average, African American kids were 69 percent as likely to receive the same diagnosis as white kids, with Hispanics only half as likely.

“Culturally sensitive monitoring should be intensified to ensure that all children are appropriately screened, diagnosed, and treated for ADHD,” the researchers concluded.

Still, some experts in the field worry about an inflationary trend in the diagnosis of children for cognitive-based behaviors deemed deviant or abnormal.

“The years pass and I see an even more frightening picture — one in which disorders in children are often given inaccurate and punitive psychiatric diagnoses and treated with inappropriate medication,” Manuel Mota-Castillo, of Holly Hill, Fla., wrote in a 2007 commentary in Psychiatric Times.

“And yet, the [two] organizations that represent the majority of American psychiatrists, the American Psychiatric Association and the American Academy of Child and Adolescent Psychiatry show no sign of worry, despite the terrible consequences that often follow when a disorder is incorrectly diagnosed and treated in emotionally disturbed young people.”

Investigators at the “Neuroscience 2013” meeting in San Diego said new findings hold promise for improved medical interventions for behaviors associated with impulsivity and aggression.

Source: Morgan, Paul L., Staff, Jeremy, Hillemeier, Marriane M., Farkas, George, Maczuga, Steven. Racial And Ethnic Disparities In ADHD Diagnosis From Kindergarten To Eight Grade. Pediatrics. 2013.

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