Individuals suffering from chronic stress have an increased risk of mental health problems such as anxiety and mood disorders. Now a new study from researchers at the University of California, Berkeley as published in the journal Molecular Psychiatry explains why stress increases the risk of mental illness.
The brain consists of two types of matter: “gray matter” and “white matter.” Gray matter consists mostly of cells – neurons, which store and process information. Gray matter also supports cells called neuroglia or glia, cells that non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for neurons in the brain and peripheral nervous system. White matter consists of axons that create a network of fibers that interconnect neurons.
Previous studies have discovered different proportions of gray matter versus white matter in individuals with stress disorders such as post-traumatic stress disorder (PTSD) compared to individuals not suffering from chronic stress. Some individuals suffering from stress disorders have excess white matter in some areas of the brain. Chronic stress therefore appears to causes the generation of more myelin-producing cells and fewer neurons than normal. As a result, the “delicate balance” of the brain becomes disrupted.
For the present study, the researchers examined the hippocampus, the area of the brain that regulates memory and emotions and that plays a role in various emotional disorders. Explains Daniela Kaufer, UC Berkeley associate professor of integrative biology, “We studied only one part of the brain, the hippocampus, but our findings could provide insight into how white matter is changing in conditions such as schizophrenia, autism, depression, suicide, ADHD and PTSD.”
The changes in the brain of individuals suffering from stress disorders suggest a mechanism for the increased risk of other mental illnesses. For example, individuals with PTSD could develop a stronger connectivity between the hippocampus and the amygdala and a lower than normal connectivity between the hippocampus and prefrontal cortex. The amygdala plays a key role in the processing of emotions including the fight or flight response. The prefrontal cortex is associated with planning complex cognitive behavior, personality expression, decision making, and moderating social behavior.
“You can imagine that if your amygdala and hippocampus are better connected, that could mean that your fear responses are much quicker, which is something you see in stress survivors. On the other hand, if your connections are not so good to the prefrontal cortex, your ability to shut down responses is impaired. So, when you are in a stressful situation, the inhibitory pathways from the prefrontal cortex telling you not to get stressed don’t work as well as the amygdala shouting to the hippocampus, ‘This is terrible!’ You have a much bigger response than you should.”
Kaufner and her research team are currently conducting more studies to confirm the hypothesis that brain changes as a result of chronic stress are the reason for the increased risk of other mental illnesses among individuals with stress disorders. The researchers are also investigating the effects of therapies, ranging from exercise to antidepressant drugs, that reduce the impact of stress and stress hormones.
New evidence that chronic stress predisposes brain to mental illness: http://newscenter.berkeley.edu/2014/02/11/chronic-stress-predisposes-brain-to-mental-illness/
Stress can make the brain more susceptible to mental illness: http://www.medicalnewstoday.com/articles/272703.php
Stress and Mental Illness: http://www.freeimages.com/photo/692911