On the Human Condition
Volume XXVIII Number 2
Joan Esterline Lafuze
Photo by Susanna Tanner
The Biology of Mental Illness
It's perhaps a natural inclination to view mental illnesses and addictions as largely moral issues. But many brain scientists have long asserted that such problems are questions of biology.
The research of Joan Esterline Lafuze, a professor of biology at Indiana University East in Richmond and a research associate at the IU School of Medicine in Indianapolis, looks into physical explanations for various social and psychological dysfunctions.
Recently, Lafuze has been working with investigators at the Institute of Psychiatric Research, in the School of Medicine's Department of Psychiatry, to explore brain mechanisms that may be responsible for the high rates of overlap between drug abuse and mental illness. In a previous study, one of her collaborators at the Medical School, Robert "Andy" Chambers, an assistant professor of psychiatry and Raymond E. Houk Scholar, described increased vulnerability to drug addiction in adult rats that had a schizophrenia-like illness. This illness results from lesions induced in the hippocampus region of the brain shortly after birth.
"The rats grow up pretty normally," Lafuze says, "but when they reach adolescence, they're challenged with addictive substances. When the rats with lesions on the hippocampus were exposed to the substance, those rats were exquisitely sensitive to that substance."
This outcome is intriguing, Lafuze says, because "there is already some evidence that something can happen in the second or third trimester of human pregnancies that disrupts the fetus's brain and is linked to the kinds of problems that we're discussing. And developmentally, rat pups are very similar to human fetuses."
Based on this work, Lafuze joined up with Chambers and Tammy Sajdyk, an assistant scientist at the Institute of Psychiatric Research who studies a brain region called the amygdala. The amygdala is implicated in anxiety and mood disorders and illnesses that affect social functioning such as autism. When lesions are introduced to this brain structure at a very early age, the rats tested in adulthood show loss of normal fear responses and abnormal social behavior. With a normally functioning amygdala, Lafuze says, "the brain knows how to incorporate a host of emotional signals, ranging from attraction to fear, into guiding appropriate social behavior." Lafuze, Sajdyk, and Chambers wondered how adult rats with neonatal amygdala lesions might respond to an addictive drug such as cocaine. So far, their results indicate that, similar to the hippocampus studies, these rats also show signs of increased addiction vulnerability.
"We already know that there is a huge overlap in humans, in terms of brain activity, between mental illness, anxiety disorders, and addiction," Lafuze says. "There are common neural pathways involved," she says, "and these animal models are confirming that observation."
How is the neural overlap manifested? "Fifty percent or more of humans with mental illness also misuse addictive substances," Lafuze says. "People who have schizophrenia, for example, have a very high rate of nicotine addiction."
A grasp of this correlation is leading to improved therapeutic approaches. "Ten years ago, you would have heard that a mentally ill person would have to become dry or sober before beginning psychiatric treatment," Lafuze says. "Now professionals are realizing that you can't treat one condition without treating the other."
Professionals are also recognizing the multi-disciplinary nature of the struggle against these disorders. "In my Biology of Mental Illness class, my students meet and hear the perspectives of at least one psychiatrist, one registered nurse, one social worker, one psychologist, one person with a mental illness, and one family member of a person with mental illness," says Lafuze.
Implications of Lafuze's research extend beyond the mental health community, as traditionally defined. She has helped law enforcement and corrections organizations reduce violent incidents by identifying the biological underpinnings of aggression. And she and co-researcher David Perkins of Ball State University have studied clergy attitudes about mental illness and the role of churches in serving congregation members who suffer from mental illness and their families.
"Marie Curie said that nothing in life is to be feared--it is only to be understood," Lafuze says."Understanding that these illnesses have a biological basis can help us live together more effectively, and that's what the research is all about."
Karen Grooms is a senior editor for the IU Office of Creative Services in Bloomington.