1 in 4 People With Depression May Have an Off-Kilter Body Clock

These markers are very recognizable, says researcher Jennifer L. Kruse, MD, an associate professor of psychiatry specializing in bipolar disorder and depression at UCLA Health in Los Angeles, who wasn’t involved in the study.

“In mood-disorders practice, we often see patients whose depression is accompanied by delayed sleep timing, evening preference, excessive sleep, severe morning tiredness, and/or seasonality, such as winter depression,” she says.

“One exciting signal is that features we can actually ask patients about are associated with differences in genetic risk and may eventually help us characterize depression more precisely and potentially prioritize targeted treatments,” says Kruse.

Nearly 1 in 4 People With Depression Experienced Symptoms of ‘Circadian Disturbance’

Researchers analyzed survey and genetic data from more than 11,000 Australian adults, most of whom had severe depression that kept coming back. In the data, scientists searched for reported markers of so-called circadian disturbance, or misalignment with the body’s internal clocks. These signs and symptoms included:

• Going to bed and waking up really late
• Changing bedtimes and wake times between weekdays and weekends
• Waking up feeling really tired
• Being a night owl
• Sleeping longer when depressed
• Experiencing severe changes in sleep, mood, and behaviors linked to the seasons

About 23 percent of participants had at least three of these six symptoms, which researchers labeled as circadian depression. The analysis found that, compared with the rest of the study participants, those with a circadian depression subtype:

• Were younger when their depression started, at around age 19, versus around age 23 for the rest of the participants
• Had more episodes of depression and more severe symptoms, including suicidal thoughts and periods of unusually high energy or mood
• Were more likely to gain weight during episodes of depression
• Said two common types of antidepressants, SSRIs (selective serotonin reuptake inhibitors) and SNRIs (serotonin and norepinephrine reuptake inhibitors), worked less well and caused more side effects
• Had higher genetic risk for attention-deficit/hyperactivity disorder (ADHD), anxiety, and bipolar disorder, as well as for higher body weight, insulin resistance, and inflammation

“Our working theory is that a disrupted body clock drives depression in this group, so treatments that target [circadian alignment] directly might help,” says lead author Emiliana Tonini, PhD, a postdoctoral research fellow at the Brain and Mind Centre at the University of Sydney in Australia.

‘Circadian Depression’ May Overlap With Seasonal Depression, but Researchers Say It’s Not Identical

Seasonal affective disorder (SAD), a type of depression that waxes and wanes with annual weather patterns, seems to involve circadian rhythm disturbances, too, but it’s a much narrower concept, says Dr. Tonini.

Seasonal mood changes are only one of the six markers of circadian depression. In the study, about 41 percent of people with circadian depression had them.

People with circadian depression were also more likely to report a bipolar disorder diagnosis and to meet criteria for atypical depression, a type marked in part by sleeping too much and weight gain, says Kruse.

“Rather than completely separate kinds of depression, these features are likely distinct but overlapping dimensions of the illness,” she says.

Light Therapy May Help Depression, but Evidence for Melatonin Is Limited

The study didn’t test light therapy or melatonin, so it can’t show that these therapies especially benefit people with circadian depression, says Kruse.

“Melatonin is more complicated, and the evidence for improving depressive symptoms is much less established,” says Kruse.

Melatonin can help shift sleep earlier in people with a sleep disorder that pushes their sleep and wake times later, but whether it also eases depression in people with strong circadian features still needs to be tested, she says.

Research on whether melatonin improves mood in young people with circadian depression is currently underway, says Tonini.

Could Circadian Depression Become an Official Diagnosis?

Right now, circadian depression isn’t part of the Diagnostic and Statistical Manual of Mental Disorders (DSM), the standard guide U.S. mental health professionals use to classify mental disorders.

More research is needed before this could become an official diagnosis, says Tonini.

Kruse agrees, saying, “The findings are a signal for follow-up rather than the final definition of a new subtype of depression.”

Strengths and Limitations of the Study

The study was large and included genetic data, but it only captured a single point in time, so it can’t show that body clock problems cause depression, only that they’re linked.

Symptoms, sleep habits, and how well antidepressants worked were all self-reported, and the circadian markers came from questionnaires rather than direct measures of the body clock. All participants were also of European ancestry, so the findings may not apply to people of different races and ethnicities.

What to Ask Your Doctor if You Have Symptoms of ‘Circadian Depression’

If you feel like sleep may be a major factor in your depression, tracking your sleep and wake times for a few days with a wearable device or a sleep diary, and sharing that information with your provider, could help guide the conversation, says Tonini.

“I wouldn’t advise asking, ‘Do I have circadian depression?’” says Kruse.

Instead, she recommends describing the pattern you experience and asking targeted questions such as:

• Could changing my sleep-wake schedule, or making it more consistent, help treat my depression or reduce the risk of future episodes?
• If so, how should I approach this?
• Does the seasonal pattern of my mood, energy, and sleep suggest that a treatment such as bright-light therapy might be worth considering?

It’s also important to share your full mood history with your doctor, says Kruse.

“Body clock problems are also common in bipolar disorder, so if your depression started at a young age or you’ve had periods of unusually high energy along with distinct mood changes, your doctor may need to look beyond depression and take a more cautious approach to treatment,” she says.