The nervous systems of people with bipolar disorders frequently make specific types of regulatory errors. Many of them involve the body’s internal clock, which controls the phenomena known as circadian rhythms. These are the regular rhythmic changes in waking and sleeping, waxing and waning activity levels, even sensations of hunger or thirst and their satisfaction. The chemical clock that governs these rhythms is located in a part of the hypothalamus gland called the suprachiasmatic nucleus, which (among other things) regulates the pineal gland’s secretion of the hormone melatonin.

You’ve probably heard about melatonin supplements sold as a cure for insomnia. Indeed, this hormone is the body’s own shut-down mechanism, and production of it usually kicks in as dusk begins. The suprachiasmatic nucleus sets itself based on the past several days’ pattern of light and dark, slowly adjusting itself in pace with the seasons. It does seem important for people to be exposed to at least some strong, direct light (sunlight or artificial) around mid-day, and for the overall patterns of dark and light to change slowly and naturally. People with bipolar disorders appear to have more difficulty in regulating this system. It’s a chicken-and-egg situation: the rhythms are disordered, so sleep, waking, and other patterns are disturbed. As insomnia, oversleeping, changes in eating habits, and higher or lower activity levels set in, the clock gets harder to reset, and the person becomes more and more ill.1

The production of the neurotransmitter serotonin is also affected by a reduced amount of light in the environment. Neurotransmitters are hormone-like chemicals that send signals to all parts of the nervous system. Serotonin affects mood, appetite, and much more. In people with bipolar disorders, serotonin and other neurotransmitters may be created in the wrong amounts, absorbed by the wrong parts of the brain or other sites, or refused admittance at sites that should accept them.

With each regulatory error, the person’s symptoms become more noticeable, and more serious. It’s like a snowball rolling downhill: eventually the circadian rhythms and other regulatory systems are completely off track, resulting in extreme mood swings, and bringing on depression, mania, or other abnormal states of mind. The affected person may start to have noticeable errors in thinking. He may even hear sounds or voices that aren’t there, feel that he’s being watched, or think that he is a special person with a great mission to accomplish.

The nervous system’s disordered condition will eventually show up outwardly as well. Movements may become rapid or very slow, jerky or super-precise. The tone and pace of speech may change. For example, speedy, disjointed speech is associated with mania.

What is it about people with bipolar disorders that permits this devastating chain reaction to occur? As of this writing, no one can point to a specific gene or brain difference with certainty, but bipolar disorders are probably caused by a complicated mix of inherited genetic differences, differences in brain structure and chemistry, unusual electrical or magnetic activity in the brain, and environmental factors.

From Bipolar Disorders: A Guide to Helping Children and Adolescents by Mitzi Walsh.