Why Bipolar Kids Can’t Get Up and Get Going
Children with bipolar disorder often have irregularities in their thermoregulatory systems. They are hot all the time—even when the ambient temperature feels cold (often very cold) to everyone else. Parents struggle constantly to get them to wear jackets in winter. In addition, it is not uncommon to see their ears turn beet red.
Scientists have found that the rapid onset of sleep occurs when the blood vessels in the skin of the hands and feet dilate and cause heat loss at the extremities. This causes the core body temperature to lower. A group of researchers, Drs. Kurt Krauchi, Christian Cajochen, and Anna Wirz-Justice, noted this functional relationship between core body temperature and sleepiness, and hypothesized that the opposite would also be true: the constriction of blood vessels would raise the core body temperature and the human being would come to a state of wakefulness. (Think colder at night and the onset of sleepiness; and warmer in the morning and the onset of wakefulness.)
The authors write:
The circadian clock prepares the thermoregulatory system for vasodilation to begin in the early evening as sleepiness increases, followed by a drop in core body temperature. Even lying down increases sleepiness by redistributing heat in the body from the core to the periphery. Turning out the light is a complex cognitive and physiological signal that also leads to vasodilation. There is a tight correlation between the timing of the endogenous increase in melatonin in the evening and vasodilation, an effect that is mimicked by pharmacological doses of melatonin. Before bedtime, then, many overlapping events orchestrate the thermoregulatory overture.
Could irregularities in the timing of melatonin release—a peptide known to reduce core body temperature and induce sleep—be a factor in the increased activity level seen at night and the marked sleep inertia seen in the morning? Melatonin, produced in the pineal gland, is secreted into the cerebral spinal fluid at dusk and diminishes its effect at dawn.
The pineal gland is a small reddish-gray structure that sits near the center of the brain. Its name is derived from the Latin word for “pine cone” because early viewers glimpsed a resemblance. The pineal gland has a story of its own.
The Pineal Gland
All vertebrates possess a pineal gland, and in certain reptiles and birds the gland is situated close enough to the top of the skull to monitor the intensity of sunlight. This “third eye” appears to help animals adjust to changes in the day-light cycles of the yearly seasons. Seventeenth-century philosopher Rene Descartes, thought the human pineal to be the seat of the rational soul; early 20th-century scientists felt that the buried-down-under human pineal had been abandoned by the roadside of human evolution.
Not so. In the mid-sixties, researchers discovered that the pineal gland secretes an important hormone called melatonin. As we mentioned above, it is a sleep-inducing hormone thought to have a part in the synchronization of circadian (daily) rhythms. In animals, melatonin influences seasonal breeding patterns. Its secretion is at the highest levels in winter.