The White Lakes Township resident would go on Facebook game binges at 3 a.m., then couldn’t focus during meetings the next day. “Half the time, even when I was awake, I was moving too slow and speaking too slow,” Carter recalls. “I just wasn’t like a functional adult.”
Then in her fifties, Carter had battled with depression since adolescence. But it was only recently that she learned that her depressed moods were linked to her off-kilter internal clock.
“People were used to thinking about psychological states as something really different from our body,” says Huda Akil, co-director of the U-M’s Molecular & Behavioral Neuroscience Institute and Pritzker Neuropsychiatric Disorders Research Consortium. “The more we study the biology of depression, the more we see they’re really closely intertwined.”
Akil and other U-M researchers are uncovering the links between depression and circadian rhythms, the biological clocks that make most people energetic in mid-morning, hungry in the afternoon, and tired at night. It turns out that the rhythms of depressed individuals–nearly one in ten Americans–are skewed. That explains their troubled sleep and eating habits, diminished sexual needs, and poor ability to concentrate–and opens a new path to treating mood disorders by resetting sufferers’ internal clocks.
U-M genetics prof Jun Li was lead author on a paper reporting the results of a study of fifty brains. The researchers noted the levels of certain hormones present in the brain at the time of death and matched them to those that are active in the brain at a given time of day. Typically, the brain secretes a stress hormone called cortisol in the morning to get ready for the day’s activities; at night, melatonin prepares the body for sleep.
For healthy individuals, Li’s team was able to develop a formula that correlated hormone levels with the person’s time of death. But the formula didn’t work for people who had suffered from mood disorders–their hormonal cycles were out of whack.
Akil said the consistency of circadian rhythms has an evolutionary basis. Early humans would forage during daylight, so our brains evolved to signal our body to be alert during the day and slumber at night.
Ellen Frank, co-director of the University of Pittsburgh’s Bipolar Institute, says that virtually all symptoms of depression run on a twenty-four-hour clock. Even suicidal thoughts and acts tend to occur at certain times. An Italian study found suicidal adolescents most often take their lives in the mid-afternoon while middle-aged people often choose times between 8 and 11 a.m.–partly because of their internal clocks.
Frank explains that most depression cases involve role changes or interpersonal struggles: transitioning from a college student to a cubicle worker, having a major dispute with a child, experiencing the death of a spouse. In the latter case, Frank says, partners have matching routines in sleep and mealtimes. “One adapts to that rhythm, and, when that partner’s no longer there, that partner is at loose ends.”
Understanding the importance of circadian rhythms, Akil says, opens new paths to treating mood disorders. Caregivers can focus on identifying disruptions in daily rhythms then look for solutions.
Carter sought help for her disordered sleep in early 2012. She calls her treatment by Dr. Deirdre Conroy at the U-M Behavioral Sleep Medicine Clinic the “linchpin” in restoring her mental health.
Carter’s therapy began with sleeping in one block from 5 a.m. to noon, then moving the starting time back fifteen minutes each day. With the assistance of small doses of melatonin, she now falls asleep between 10:30 and 11 p.m. and wakes up before 9 a.m. Carter also exercises for a half-hour every day and eats at typical mealtimes.
Regaining pleasures she’d missed as a night owl, Carter is again enjoying jaunts to the movie theater and inviting people to her home. Retired in her early sixties, she sees herself on an upward trend: “I feel like my world has expanded,” she says.
