The American Society of Addiction Medicine (ASAM) five years ago re-defined addiction as a chronic brain disorder, not just a behavioral issue.
“The theory seems to have a lot of validity. Addiction changes areas in the brain related to motivation and primacy of reinforcement for salience,” said Michael M. Miller, M.D., past president of ASAM, medical director of the Herrington Recovery Center at Rogers Memorial Hospital in Wisconsin and chair of the committee that issued the new definition.
Other research is now exploring a connection between the brain and mental health diagnoses.
Genetics is one of the risk factors that plays a role in brain development, according to Larry J. Seidman, Ph.D., director, Commonwealth Research Center, Professor of Psychology at the Harvard Medical School Department of Psychiatry, and vice chair (Research), Massachusetts Mental Health Center Public Psychiatry Division of the Beth Israel Deaconess Medical Center.
Family history is a common indicator for transmitting genetic risk for a mental illness. “For instance, one in 10 offspring of a parent with schizophrenia will develop schizophrenia,” he said. “In the general population, the risk is one out of 100.”
Seidman noted that alterations in the brain can occur for different reasons and can have different effects.
“There is substantial research with pregnant women that has found infections or substance abuse during pregnancy or physical trauma during the birth process can result in damage to the brain,” he said.
“For example, diabetes or malnutrition in the pregnant mother can affect the baby’s brain. Sometimes a baby may experience changes to the brain if the umbilical cord becomes wrapped around the baby’s neck during birth, resulting in a reduction of oxygen to the brain.”
Neurodevelopmental changes early in a person’s development, may also be linked to a mental illness.
“Autism is a classic neurodevelopmental disorder. From conception, the brain didn’t get wired right or something went wrong during pregnancy so the baby’s brain is altered early on,” Seidman said.
Seidman explained that research shows that copy number variants (CNV), which are pieces of DNA that are deleted or duplicated, may be found in a modest number of people with autism or schizophrenia.
“Most people with mental illness don’t have a CNV, but when they do, it may have significant effects,” he said, adding that several studies have found a correlation between the brain and CNVs.
Neurodegenerative changes typically take place later in life and may also alter brain chemistry, according to Seidman.
Some studies on neurotransmitters in the brain, e.g., serotonin and norepinephrine, have explored their connection to depression, anxiety, schizophrenia and bipolar disorder, according to Karen A. Holler, Ph.D., neuropsychologist at Bradley Hospital, Children’s Inpatient Unit, and pediatric neuropsychologist at Butler Hospital.
Attention deficit hyperactive disorder, which is a seemingly straightforward condition, has also been clearly linked to brain function.
“It may sound like a simple diagnosis, but there are so many steps in the process of paying attention. You need the right arousal level. Is the person oriented to the stimuli? Can they shift focus and sustain attention? There are a million pieces involved in regulating attention and, ultimately, all are linked to emotional salience,” Holler said.
Another potential brain-related factor that may contribute to the development of a mental illness is inflammation.
Holler pointed out that Crohn’s disease, obesity, multiple sclerosis and diabetes all involve an inflammatory process that can impact brain function.
For example, exploratory studies have shown that children who get strep throat sometimes present with acute onset obsessive compulsive traits or tics presumably related to inflammation.
And theories on the impact of stress on the brain present an “interesting concept,” Holler pointed out.
“It’s not necessarily bad to be exposed to some stress. It helps you learn coping skills. When it becomes toxic is the problem and can impact brain development,” she said.
“Elevated stress increases cortisol, which can damage the neurons. For instance, a child exposed to domestic violence experiences a toxic level of stress. We suspect that has a measurable impact on processes such as executive control.”
Brain development is never static, added Holler.
“Most believe that at 25, development is done as far as morphology is concerned and at 30, it is done with myelination. But myelination may actually continue past 30.”
Maintaining adequate brain functioning through crossword puzzles and number games can help “keep the iceberg above water,” she added. “There are lots of programs on the market. The jury is out on their long-term effectiveness, but it’s not a bad idea. It could be useful, but if you stop practicing, you might go back to baseline.”
The debate over the complexities of nature versus nurture has gone on for years, noted Stephen D. Sarfaty, Psy.D., director, Comprehensive Neuropsychological Services in Cheshire, Connecticut.
“The genetic makeup [of the brain] is powerful, but it’s also true that our conditioned development of the brain is powerful. Early experiences give us what we’ve inherited and our environment exposes us [to other factors],” he said. “How we cope develops or fails to develop neuronal patterns in the brain. So there is a strong relationship between nature and nurture.”
Sarfaty added that, even though we don’t live in the same environment as our caveman ancestors, we have the same hardwiring in the brain. “We all live with stress and get alarmed. The brain sends neuroendocrinal signals in response to stimuli. We have to have exposure to shut it off. But it won’t have the same effect on everyone,” he said.
For instance, three soldiers involved in a traumatic situation may have different responses. One may develop posttraumatic stress disorder, another may be unaffected and the third may become more resilient. “Stimuli doesn’t translate as a one-to-one predictability of a pathological state,” Sarfaty said.
In the last 20 years, there have been major developments in tools to objectively measure brain function, according to Sarfaty. “We’ve learned so much and have so far to go. There are fundamental challenges to making progress. There is a huge delay between accumulation of scientific evidence and translation to clinical care,” he said.