Too often the general public relegates mental illnesses like depression, bipolar disorder, and schizophrenia to just that, mental illness, diseases of the mind. However, with modern science, we are beginning to see more and more the folly of this simplistic viewpoint. We are now seeing the science behind these illnesses; the changes in brain form, function, and chemical balance that alter how our brain functions and perceives the world around us. For the next month or so, in my “Exploring the Science of…” mini series, I will be talking about how what happens in our brain impacts what happens in our mind. In this post, I will be talking about how subtle changes in the brain can lead to bipolar disorder.
What is Bipolar Disorder?
Bipolar disorder consists of hyperactive episodes called “manic” episodes, as well as episodes of depression called “depressive” episodes. During manic episodes, a person may feel unstoppable, stop sleeping, and generally feel extremely happy, active, and outgoing, sometimes engaging in high risk behaviors. Depressive episodes are similar to those found in depression, and the person may feel tired, in slow motion, or hopeless for extended periods of time.
There are several sub-diagnoses within bipolar disorder. These include Bipolar I, categorized by full blown manic episodes, as well as Bipolar II, in which depressive episodes and more mild manic episodes are present. Other diagnoses include Cyclothymia and Bipolar Disorder – Not Otherwise Specified (BP-NOS).
It’s All in the Genes
Like so many things, mental illness is often impacted by genes. This has been shown through familial studies for mental illness, along with ever helpful twin studies. These studies give a strong case for mental illness having a genetic component, helping to explain why mental illness so often runs in families. Bipolar disorder is no exception, in fact over half a dozen genes have been implicated in the formation of bipolar disorder. These genes affect everything from your biological clock to how your body handles neurotransmitters like serotonin. Mutations of these genes can cause anything from anxiety, to depression, to increased chance of alcohol abuse, and leaves the person at a higher risk of developing bipolar disorder.
Those of you who have extensively studied mental illness may have noticed an underlying similarity between the symptoms of many disorders. For instance, psychosis can be present in schizophrenia, depression, bipolar disorder, and sometimes even (in milder forms) extreme anxiety. Similarly, some of the gene mutations in bipolar disorder are the same gene mutations implicated in schizophrenia. Furthermore, mutations in specific genes cause the same symptoms across both disorders. For example, a mutation in a certain gene causes hallucinations in both schizophrenia and bipolar disorder.
Think On It
As mentioned previously, often people with bipolar disorder engage in high risk behaviors during manic episodes. With modern technology, we are now getting a glimpse into why this might be. The (potential) answer lies in two parts of the brain, and their function relative to healthy subjects. These two parts are the medial prefrontal cortex, responsible for decision making and memory, and the anterior cingulate gyrus, correlated with emotional response and control.
In those with bipolar disorder, the medial prefrontal cortex is under active compared to healthy controls, while the anterior cingulate gyrus is overactive. This basically means that less energy is going into decision making, and more into emotion. This difference, however subtle (we’re talking about minor differences in tiny parts of the brain), may lead to clues about the poor decision making often found in bipolar disorder.
Sleep is an integral part of our mental health, especially so when it comes to bipolar disorder. A decrease in sleep is almost always correlated with an increase in bipolar symptoms, and a return to a normal schedule is usually met with decreased symptoms. But what explains this phenomenon? What exactly is going on in our brain when we go without sleep?
The most important change that happens when we forgo sleep happens inside our amygdala, the brain’s center for emotion. Without sleep, the amygdala becomes overactive, meaning it is more sensitive to emotional stimuli. Remember when we talked about overactivity in the anterior cingulate gyrus which also controls emotion? Now imagine that plus an overactive amygdala. That spells trouble. It’s no surprise then that going without sleep worsens symptoms in those with bipolar disorder.
Bipolar disorder is a complex disease that is just beginning to be understood by scientists. As we begin to learn more about this disorder, we may find clues into the treatment and early identification of the disorder. With this information, we can help better the lives of millions who have bipolar disorder. Also of interest is bipolar disorders link to other disorders such as depression and schizophrenia. Already scientists have discovered similar genetic roots for these disorders, and who knows what the future holds.
The National Institute of Mental Health