Daijiworld Media Network - New Delhi
New Delhi, Oct 22: A genetic analysis has identified a new subtype of depression linked to the body's internal 24-hour clock, which regulates sleep-wake cycles. Researchers have termed the condition “circadian depression”.
The study involved a clinical and genetic analysis of more than 10,000 people with depression, using data from the Australian Genetics of Depression Study. The findings, published in the British Journal of Psychiatry, suggest that circadian depression affects around one-fourth of people in the study who experienced severe, recurrent or persistent depression.
“Our research has identified circadian depression as a new subtype, affecting around a quarter of people in our study into those with severe, recurrent or persistent depression,” said Emiliana Tonini of the University of Sydney's Brain and Mind Centre, the study's first author.
Symptoms associated with the subtype include seasonal patterns of illness, sleeping longer during depressive episodes, waking up feeling extremely tired and being more active at night.
Tonini said understanding the different subtypes of depression could help patients gain earlier access to treatments that are more effective for their condition.
According to the researchers, circadian depression appears to respond less effectively to commonly prescribed serotonin-based antidepressants but may respond better to behavioural and medical therapies targeting the body's internal clock. These include melatonin, melatonin-targeted antidepressants and light therapy.
The findings also offer insights into the genetic mechanisms underlying the condition and why traditional treatments, including selective serotonin reuptake inhibitors (SSRIs), may be less effective for some patients.
Researchers found that people with circadian depression were more likely to experience depression earlier in life and report more severe symptoms, including mania and higher levels of suicidal thoughts. They also had a higher genetic risk of inflammatory and cardiovascular conditions, as well as major neurodevelopmental disorders such as attention-deficit/hyperactivity disorder (ADHD).
SSRIs and serotonin-norepinephrine reuptake inhibitors (SNRIs) work by preventing nerve cells from reabsorbing certain chemical messengers, helping regulate mood and ease anxiety. These medicines are commonly used as first-line treatments for depression, but the study suggests they may be less effective and cause more side-effects among people with the circadian subtype.
Dr Ian Hickie, co-director of the Brain and Mind Centre and a clinical psychiatrist, said failure to recognise circadian depression in young people could contribute to unsuccessful early treatment and increased side-effects.
“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,” Hickie said.