One in four people with depression may suffer from this new type

Scientists have identified a new subtype of depression that may be affecting as many as one in four patients, a discovery that could lead to new medical and behavioural treatments.

This could explain why traditional antidepressant treatments such as selective serotonin reuptake inhibitors (SSRIs) do not work well for some people.

“Depression is not a uniform illness and understanding the characteristics of different subtypes means that we can give people earlier access to treatments that will be most effective for them,” said Emiliana Tonini, an author of a new study detailing the condition published in the British Journal of Psychiatry.

The newly identified condition, called “circadian depression”, is linked to the body’s 24-hour internal clock that regulates our sleep-wake cycle.

It is characterised by being more resistant to common antidepressant treatments, researchers from the University of Sydney say.

But it can be more responsive to therapies targeting the body clock’s unique brain circuits, such as melatonin, melatonin-targeted antidepressants and light therapy.

Not recognising circadian depression in young people often leads to early treatment failures and more side effects, scientists warn.

“Our research has identified circadian depression as a new subtype, affecting around a quarter of people in our study in those with severe, recurrent or persistent depression,” Dr Tonini said.

In the study, scientists conducted genetic analysis of more than 10,000 Australians with depression.

Nearly 25 per cent – 2,604 participants – were identified as having circadian depression, with symptoms including a seasonal pattern of illness, sleeping longer when depressed, waking feeling very tired, and being a night owl.

People with this condition were more likely to experience their depression emerging earlier in life, were more commonly female, and had more severe symptoms.

They also had a higher genetic risk for inflammatory and heart health problems, as well as major neurological disorders like ADHD, anxiety, and bipolar disorder, the study noted.

“Because circadian depression is linked to people’s internal body clock, treatments targeting the circadian rhythm, such as light therapy and melatonin, may be much more relevant, and clinicians should reach for these much earlier in people with this presentation,” said Jacob Crouse, another author of the study.

“For those who find that antidepressants are not working for them, it is important to speak to your clinician for advice about your individual circumstances.”

Scientists called for future research on a much larger and more diverse population to validate their findings.

If you are experiencing feelings of distress, or are struggling to cope, you can speak to the Samaritans, in confidence, on 116 123 (UK and ROI) or visit the Samaritans website to find details of your nearest branch.

If you are based in the USA, and you or someone you know needs mental health assistance right now, call or text 988, or visit 988lifeline.org to access online chat from the 988 Suicide and Crisis Lifeline. This is a free, confidential crisis hotline that is available to everyone 24 hours a day, seven days a week. If you are in another country, you can go to www.befrienders.org to find a helpline near you.