Aussie researchers have identified a new type of depression

What is circadian depression? Researchers say this subtype isn’t like the others

• What is circadian depression?

• 6 warning signs of circadian depression

• Risk factors for circadian depression

• Why early identification is crucial

• How is circadian depression treated?

Circadian depression is a new subtype of depression, according to Australian researchers who say morning tiredness, night owl tendencies and seasonal mood patterns are among the common symptoms.

Researchers from the University of Sydney have identifieda new subtype of depression that’s based around the body’s internal clock, known as the circadian rhythm.  

Circadian depression stems from disruptions to the body’s circadian rhythm, which can not only throw off our sleep-wake cycle, but also contribute to a range of mood and overall health symptoms. 

The study considered over 10,000 Australians and found that circadian depression accounted for nearly a quarter of patients with severe, recurrent or persistent depression, and was more common in young people. 

But experts say this about more than just sleep – here’s what can cause circadian depression, and why experts say individualised treatment is so important. 

Symptoms of circadian depression develop around the body’s sleep-wake cycles, according to co-director of the Brain and Mind Centre Professor Ian Hickie.

“Circadian means “about a day”; it’s your 24-hour clock,” Prof Hickie explains. 

He says it’s not just about sleeping, but how light, motor activity and eating behaviours can trigger melatonin and regulate the body’s patterns, or “clocks”. 

“The coordination of those clocks underpins your mood, your metabolism, your concentration, your sleep-wake cycle, and many other key factors,” Prof Hickie adds.

“When it’s off, you feel jet-lagged, tired and exhausted, you gain weight, you can’t concentrate, you sleep poorly, your behavior changes and you tend to graze rather than eat in normal patterns; it all becomes disconnected.”

In their recent study, researchers from The University of Sydney’s Brain and Mind Centre considered data from adults with depression, and analysed how their symptoms might align to the new circadian depression subtype.

The study’s first author Dr Emiliana Tonini says the symptoms of circadian depression include: 

1. Seasonality:Experiencing a seasonal pattern of mood, sleep or behaviour.
2. Delayed sleep timing or midpoint:Having a delayed sleep rhythm or disrupted regularity.
3. Social jet lag:Where sleep timings vary between work days and “free” days. So, someone might go to bed and wake up at different times throughout the week, which creates a sort of jet lag effect due to social obligations or activities. 
4. Night owl tendencies:Having a preference for night activity.
5. Hypersomnia:Sleeping for a long period of time, especially when depressed.
6. Morning tiredness:Feeling tired, even after waking from a long night’s sleep.

Circadian depression can be more common in young people.

“The age of onset of their depression was younger compared to those with non-circadian depression,” Dr Tonini says, about the study’s findings.

“(People with circadian depression) also had more episodes and more complex trajectories: More suicidality, more hypomanic and psychotic-like symptoms as well.” 

Prof Hickie says women were more affected by circadian depression than men, but further research is needed.  

“In these particular studies, we found more women to be affected,” he explains.

“More women volunteer for these studies, but … a disturbed circadian clock may have other biological effects on women on other aspects of their biology, particularly their hormonal cycles and metabolic impacts.” 

Demographics aside, Prof Hickie says our modern lifestyles often disrupt the sleep-wake cycle and may contribute to circadian depression. 

“People stay up later, they spend more time inside … we spend more time in light in the evenings,” he says.

It’s the opposite rhythm of what our body needs to thrive.

Even if it’s the dim TV or phone light at night, Dr Tonini says “our circadian system is quite sensitive to it”. 

Circadian depression doesn’t respond well to conventional depression treatments, which is why it’s so important to identify early. 

“If you get on the wrong track, the traditional (treatment) that’s typically recommended, you’re likely to have bad experiences, less response to treatment and more side effects,” Prof Hickie stresses.

Currently, he says approaches are quite generalised.

“(Clinical guidelines) largely assume that anxiety is the main factor and that generic treatments with psychological therapy, particularly standard cognitive behavioral therapy, and standard antidepressants will be equally good for all.”

But when it comes to circadian depression, he says it’s critical that treatments focus on “the sleep-wake cycle, particularly in the behavioral line to do with morning light exposure, daylight activity, regularity of sleep-wake cycles and regularity of food schedules”.

Unlike standard depression, which relies heavily on generic cognitive therapy or conventional SSRIs (selective serotonin reuptake inhibitors), circadian depression is responsive to behavioural and medical therapies targeting the body clock’s unique brain circuits, such as melatonin, melatonin-targeted antidepressants and light therapy.

The 5-step clock reset 

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It’s unlikely to be one intervention alone that shifts the body clock. Instead, Prof Hickie says a combination of things can change what’s signalled to the brain for an overall effect.

Try implementing these five clock-reset habits: 

• Keep a regular sleep schedule: Go to bed and wake up at the same time seven days a week to eliminate social jet lag.
• Wake as close to sunrise as possible: This signals an immediate end to nighttime melatonin production.
• Seek midday sun: Spend time outside in the middle of the day, when the light is brightest.
• Move at sunset: Be outside and physically active around sunset.
• Close the kitchen early: Avoid large meals late at night.