Study Finds Circadian Patterns in 23% of People With Depression

A study of more than 10,000 Australians with depression found that 23% fit a profile linked to disrupted circadian rhythms—the body’s roughly 24-hour timing system. The finding points to a possible way of describing differences among people with depression, but it doesn’t establish a separate diagnosis or show that a particular treatment works better for this group.

Published in the British Journal of Psychiatry, the research analyzed clinical and genetic information from participants in the Australian Genetics of Depression Study. Researchers used participants’ self-reports to assess patterns including social jetlag (a mismatch between a person’s internal clock and daily schedule), seasonal mood changes, later sleep timing, being a night owl, morning tiredness, and excessive daytime sleepiness.

The researchers argue that these features may form a clinically useful profile and could eventually help tailor care. For now, circadian depression remains a proposed subtype. It isn’t a formal diagnosis in the DSM-5, the manual mental health professionals use to classify psychiatric conditions, and the study does not prove that circadian disruption causes depression.

What the profile may involve

The researchers describe this profile as depression accompanied by circadian disruption: a mismatch between the body’s internal timing and a person’s surroundings or routine. People in the group showed disrupted sleep-wake cycles, less daytime activity, low energy, and weight gain during depressive episodes. They were also more likely to have depression begin at a younger age and to show features associated with mania.

Within the study group, people classified under the circadian profile were more likely to be night owls and to experience insomnia. About 80% were female. Researchers also found higher rates of severe depressive symptoms, including mania, suicidal thoughts, psychological distress, and physical symptoms such as pain or fatigue. The group was more likely to report weight gain during depressive episodes and had a weaker response to antidepressants in the study data.

ADHD, anxiety, bipolar disorder, overweight or obesity, and insulin resistance were also more common in this group than among participants with other depression profiles. These are associations reported in the study; they don’t show that circadian disruption causes these conditions or that people with them necessarily have circadian depression.

Why body-clock timing matters

The circadian system helps coordinate sleep and alertness, hormone release, and metabolism. Thea Gallagher, Psy.D., a clinical associate professor at NYU Langone Health, says that when the body’s timing and daily life fall out of step, sleep and biological processes involved in mood may be affected.

Sleep and mood can then influence each other. Irregular or disrupted sleep may make it harder to manage emotions and stay involved in daily activities; depression, in turn, can make sleep and routines less regular. This feedback loop offers one possible explanation for why sleep timing deserves attention in depression care, while leaving open which changes matter most and for whom.

W. Christopher Winter, M.D., a neurologist and sleep medicine physician, emphasizes that circadian disruption differs from simply getting too little sleep. In his view, a fairly consistent schedule with somewhat insufficient sleep may affect a person differently from a schedule that shifts substantially from day to day, even when total sleep time is adequate. The study did not test that comparison directly, so it should be understood as clinical perspective rather than a result established by this research.

What the findings mean for care

The study doesn’t establish a new diagnostic checklist. Being a night owl, waking tired, or having insomnia alone does not mean someone has depression or this proposed subtype. Gallagher advises people who are concerned about depression to seek an assessment from a mental health professional, who can consider mood symptoms, sleep patterns, and other possible explanations, including sleep disorders. A short record of sleep timing, mood, energy, and seasonal changes may help a clinician identify patterns.

There’s no set treatment for circadian depression because it isn’t yet a formal diagnosis. Gallagher says the findings don’t show that people who match the profile should change or stop medication. Rather, they suggest that clinicians may want to consider sleep and circadian timing alongside established depression care.

The study authors report that standard antidepressants, including SSRIs and SNRIs, may be less effective and cause more side effects for people in this group. That result calls for further study: it doesn’t mean these medicines won’t help an individual, or that someone should alter treatment without discussing it with their prescriber.

Approaches that aim to align the body clock, sometimes called chronotherapies, could warrant research. These include light therapy, melatonin, and changes in the timing of exercise or sleep. The study does not establish which approach works, when it should be used, or whether it’s suitable for a particular person. Melatonin can affect sleep timing, but the source experts’ comments aren’t a treatment recommendation. Anyone considering it, light therapy, or a change to medication can discuss the options with a doctor or pharmacist, especially when managing other conditions or medicines.

For insomnia, cognitive behavioral therapy for insomnia (CBT-I) may also be worth discussing with a clinician. The practical message is to bring persistent mood concerns and sleep-pattern changes into the same conversation. Further research will need to test whether this profile can be identified reliably and whether treatments that address timing improve outcomes.