Scientists Propose New Depression Variety Linked To Body Clock

Adults With Body Clock Depression Report Weaker Antidepressant Relief

Some people with depression stay up late, sleep far longer than usual during bad stretches, and wake up exhausted. University of Sydney scientists say that pattern may mark a distinct type of depression, called a circadian subtype, tied to the body’s internal clock. It showed up in nearly 1 in 4 adults with severe, recurring depression in their Australian study. People with it also reported less relief from two widely used types of antidepressants, and the researchers argue that light therapy and melatonin deserve a much earlier look.

Published in The British Journal of Psychiatry, the study drew on survey and genetic data from 11,380 adults. People in the circadian group started having depression earlier, around age 19 instead of 23, and reported more intense symptoms, including suicidal thoughts and manic-like experiences. More than half had gone through ten or more episodes, compared with just over a third of everyone else.

Co-senior author Jacob Crouse of the university’s Brain and Mind Centre said treatments targeting the circadian rhythm, such as light therapy and melatonin, “may be much more relevant” for these patients. Those treatments were not tested in the study, and the authors call their findings “an initial exploration.”

Circadian Subtype of Depression Appeared in 23 Percent of 11,380 Adults

Data came from the Australian Genetics of Depression Study, a nationwide project that enrolled adults diagnosed with depression at some point in their lives. Participants were recruited through government prescription records or a public media campaign. The adults in this analysis were of genetically inferred European ancestry, about three-quarters were women, and the average age was roughly 44. Across the full study, the typical participant had been through six depressive episodes, and about two-thirds had experienced suicidal thoughts.

Participants filled out online surveys about their sleep, mood, and experiences with ten commonly prescribed antidepressants. Researchers then looked for six body clock traits: sleep schedules that swing between work days and days off, moods that shift with the seasons, unusually late sleep timing, strong night-owl tendencies, heavy tiredness right after waking, and sleeping much more than normal during depressive episodes. Anyone with at least three landed in the circadian group, which came to 2,604 people, or 23 percent of the sample.

Circadian Subtype of Depression Linked to Higher Genetic Risk and More Distress

Compared with everyone else, the circadian group was younger (about 38 versus 46 on average) and more often female (80 versus 73 percent). Members also reported more psychological distress, unusual perceptions or beliefs, and bodily complaints.

DNA told a similar story. Researchers tallied how many gene variants each person carried that are linked to certain traits and conditions. The circadian group carried somewhat more of those tied to depression, ADHD, anxiety, bipolar disorder, insomnia, and body weight, though the differences were small. The strongest link of all was to variants tied to being a night owl. Those patterns hint that these symptoms reflect more than overlapping sleep problems, though independent research must confirm whether they point to a biologically distinct form of depression.

Circadian Subtype of Depression Tied to Weaker Antidepressant Relief

Participants rated how well each antidepressant had worked for them. The circadian group reported less relief from two of the most widely used types, SSRIs and SNRIs, which work on serotonin and related brain chemicals, and more side effects such as drowsiness, muscle pain, nausea, and anxiety. The gaps were modest, and two other drugs, amitriptyline and mirtazapine, showed no clear difference.

One explanation the authors float is that standard medications, which act on brain chemicals, may not do enough to correct a body clock running off schedule. Authors say clock-focused approaches, including dimmer evenings and regular sleep and wake times, may benefit people with depression and disrupted sleep rhythms.

Ian Hickie, Co-Director of the Brain and Mind Centre, said that missing this pattern in young people often leads to early treatment failures and more side effects, and that most young people are offered SSRIs first. First author Emiliana Tonini put the broader point simply: “Depression is not a uniform illness.”

Today, treatment guidelines mostly sort depression by how severe it is or how often it returns, not by what is driving it, which often sends patients through rounds of trial and error with medication. A subtype tied to the body clock could point some of them toward different options sooner.

Because those ratings came from memory at one point in time, the study cannot show that a disrupted body clock causes the weaker response. It also enrolled only adults, so findings in teenagers remain untested. Results do not mean everyone who struggles with antidepressants has a body clock problem.

Confirming that the group is real is the next job. Until then, the finding describes one Australian sample made up largely of severe, recurring cases, not depression as a whole.

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Disclaimer: This article is based on a published research paper and a university press release and is intended for general informational purposes only. It is not medical advice. Anyone struggling with depression or with their current medication should talk with a qualified health professional before making any changes to treatment.

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