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A new study from Australian researchers has identified a new subtype of depression “circadian depression”, that is thought to be linked to a disruption to the 24-hour internal body clock, which regulates the body’s sleep-wake cycle.
The study found that participants who presented with this subtype were younger and more often female and reported experiencing an earlier onset of depression.
The study, published in the British Journal of Psychiatry earlier this month, found that of 11,380 participants with severe and recurrent depression, 23% were identified as being affected by circadian depression.
Dr Emiliana Tonini, the study’s first author, of the University of Sydney’s Brain and Mind Centre said researchers defined circadian depression as being present in participants who displayed at least three out of the six criteria:
- Experienced a seasonal pattern of illness
- Delayed sleep timings
- Sleeping longer when experiencing depression
- Being an evening type or ‘ a night owl’
- Feeling very tired upon waking
- Experiencing social jetlag, where sleep patterns vary significantly between the work week and weekends
Treatments for circadian depression
Researchers believe the new subtype to be less responsive to conventional antidepressant treatments, such as selective serotonin reuptake inhibitors (SSRIs) and serotonin–noradrenaline reuptake inhibitors (SNRIs). The research suggests that beneficial treatment for circadian depression could include light therapy and melatonin, both of which target the body’s circadian rhythm and unique brain circuits.
Co-senior author Dr Jacob Crouse from the Brain and Mind Centre urged clinicians to reach for treatments like melatonin and light therapy earlier for people who present with the circadian subtype. Dr Jacob Crouse said, “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…”
The research showed that people with circadian depression were more likely to experience hypomanic and psychotic-like symptoms and were at a higher risk of suicidal ideation and attempted suicide. People with circadian depression were also found to have a higher genetic probability of ADHD, and mood disorders.
Professor Ian Hickie, Co-Director of the Brain and Mind Centre and a clinical psychiatrist, highlighted the importance of recognising circadian depression early in young people to avoid treatment failures and additional side effects. Professor Ian Hickie said, ” We really want young people to receive the most appropriate treatment early in their course of illness. Most young people will be offered SSRIs first up, but for at least a quarter there are better circadian-focused medical and behavioural options to help treat and manage their condition.”
The researchers said the “study strengthens the evidence base for a circadian subtype of depression as a biologically valid and clinically useful phenotype of depression” and experts hope that the identification of this new subtype will lead to more alternative and targeted behavioural and medical treatments.
Dr Emiliana Tonini said at a press briefing, “Depression is not a uniform illness and understanding the characteristics of different subtypes mean that we can give people earlier access to treatments that will be most effective for them.”
