Urban legends posit that the moon and its lunar cycles affect human health, but most of those allegations aren’t up to scientific snuff. A few examples: Menstrual cycles are not correlated with an orbiting moon, full moons don’t drive us crazy, and the appearance of a blood moon doesn’t mean the apocalypse has arrived. But there is at least one aspect of human health that appears to be tied to the lunar cycle, and it’s the focus of a bizarre new study published in Translational Psychiatry.

According to first author and scientist emeritus at the National Institute of Mental Health Dr. Thomas Wehr, bipolar disorder can be triggered by celestial movement.

Wehr makes this argument in a case study about a 51-year-old man diagnosed with a rapid-cycling bipolar disorder. People with disorder go through four or more distinct episodes of depression, mania, or hypomania in a one-year period. In the paper, Wehr writes that this man was just one participant in an 18-patient study on manic-depressive cycles, but what made him stand out was the fact that he had kept careful, multi-year records of his mood and sleep. These records allowed Wehr to examine how the lunar and solar cycles affected the patient’s health.

The episodes of mania and depression that typically accompany bipolar disorder are accompanied by dramatic changes a person’s sleeping habits. When a person is depressed, they sleep a lot, and when they are feeling manic, they hardly sleep at all. Some scientists think this means that sleep disturbances aren’t just a symptom of bipolar disorder; rather, sleep (or lack thereof) could actually be the cause. This, in turn, might have to do with the lunar and solar cycles.

bipolar disorder
Charts following the patient's mood and sleep cycle.

Because sleep is regulated in part by the circadian pacemaker, the small group of cells that control the circadian “internal clock”, Wehr hypothesized that people with bipolar disorder may have irregular circadian rhythms. Usually, the circadian pacemaker keeps time with the 24-hour rhythm of the solar day. But in people with bipolar disorder, Wehr argues, these cells may have “uncoupled” from the solar cycle and become fixed to the 24.8-hour rhythm of the lunar tidal day.

The patient’s sleep and mood records revealed that at each new moon, which happens every 29.5 days, the man experienced one or more nights of total insomnia and shift from feeling depressed to manic. But when he stuck to a rigid schedule of sleep during long periods of darkness every night, writes Wehr, “the lunar signal disappeared and his mood cycling stopped.” These periods of darkness seemed to stabilize his moods and increase the circadian pacemaker’s ability to respond to light, allowing the man’s circadian pacemaker to couple to a more normal day-night schedule.

“These results support the hypothesis that interference between two components of the circadian system that were separately entrained to the solar day and the lunar tidal day generated the mood cycles,” Wehr explains. “Although skepticism is warranted, lunar mood cycles may be an experiment of nature that is pointing towards aspects of gravity and biophysics that are only beginning to be investigated.”

While better, longer, and darker sleep helped this patient, the first step for anyone who thinks he or she may have bipolar disorder is talking with a doctor or a licensed mental health professional. Effective treatment plans usually consist of a combination of medication and psychotherapy.