Many people with depression don’t respond to existing treatments, and scientists believe this may be due to the many different pathways people can take to arrive at the same depressive symptoms.
A new study has found that a quarter of patients enter a subtype of “circadian” depression, resulting from a state of perpetual jet lag.
Led by psychiatric researchers Jacob Crouse and Ian Hickie, a team from the University of Sydney in Australia published their findings in the British Journal of Psychiatry.
Current clinical guidelines treat depression as a single disorder. But Hickie and his team believe that while depression may seem similar for each patient, many different biological issues can be causing the symptoms.
Most available treatments for depression assume that the disorder is underpinned by anxiety. But for the 30 percent of young people suffering from atypical depression, that’s not the case.
So, Hickie asks, if it’s not driven by anxiety, then what’s driving it?
“What we have been studying for some time now is the neurobiology of the brain regulators of the circadian system,” he explains.
))>
Our body’s circadian systems are those aligned with the 24-hour day and night cycle, with light being the primary signal modulating these systems. But every body is a little different.
“The coordination of these clocks underpins your mood, metabolism, concentration, sleep/wake cycle, and many other key factors,” says Hickie.
“When it’s off, you feel jet lag all the time. You feel tired, you feel exhausted, you gain weight, you can’t concentrate, you sleep poorly and your behavior changes.”
Hickie and his colleagues have now found evidence that this fundamental mechanism is indeed behind some of the mood disorders, in data from 11,380 participants in the ongoing Australian Study of the Genetics of Depression.
Researchers define the circadian subtype of depression with six criteria.
For someone with circadian depression, their symptoms will change with the seasons, due to the changing length of days. Second, half of their sleep is delayed compared to the general population.
They also experience social jet lag: that is, their sleep midpoint on work days is several hours different from the midpoint on non-work days (i.e., their sleep tendencies do not match the timing around which society is typically designed).
They have an evening chronotype, and when given the chance, they sleep longer than the typical person (perhaps, researchers suggest, due to the constant experience of jet lag). Not surprisingly, they also report being very tired in the morning.
Among the 11,380 people included in this study, approximately 1 in 4 patients correspond to this circadian subtype.
There was some overlap with other proposed subtypes of depression. The largest crossover was for atypical depression, but even then, about 1,400 cases met criteria for atypical depression but not the circadian subtype, suggesting that they may still be distinct forms of the disorder.
“Depression is not a uniform illness and understanding the characteristics of different subtypes means we can give people quicker access to treatments that will be most effective for them,” says Emiliana Tonini, first author of the new paper.
Participants in the circadian subtype began experiencing depression earlier in life and reported more severe clinical symptoms like mania, psychosis, and suicidal tendencies.
They were also more likely to gain weight during depressive episodes. They also had a higher genetic risk for major neurodevelopmental disorders, including ADHD, as well as inflammatory and cardiovascular health conditions.
These participants were also less likely to find common antidepressant medications effective and tended to experience more side effects from the medications.
“Since circadian depression is linked to people’s internal biological clock, treatments targeting the circadian rhythm, such as light therapy and melatonin, may be much more relevant, and clinicians should apply them much earlier in people with this presentation,” says Crouse.
“For those who find that antidepressants are not working for them, it is important to speak to your clinician for advice about your personal situation.”
If this story has raised concerns or you need to talk to someone, please use this list to find a 24/7 crisis hotline in your country and seek help.
The research was published in British Journal of Psychiatry.
This article was fact-checked by Fiona MacDonald and edited by Fiona MacDonald. Although we are proud of our process, we are only human. If you spot an error, please let us know.
Gn Health
