New Subtype of Depression Linked to Internal Body Clock Identified
Research suggests that a dysregulated circadian rhythm may be the cause of 'circadian depression' in approximately one in four individuals experiencing depressive symptoms.
Recent studies have identified a novel subtype of depression, dubbed 'circadian depression,' which may be triggered by disruptions in the body's internal 24-hour clock. This internal clock, known as the circadian rhythm, governs crucial bodily functions including hormone regulation, digestion, mood, and sleep-wake cycles.
When this internal clock is out of sync, individuals may experience symptoms akin to constant jet lag, including persistent fatigue, exhaustion, weight gain, difficulty concentrating, poor sleep, and altered behavior. Lead researcher Ian Hickie described this state as feeling "jet-lagged all the time."
The findings, published in The British Journal of Psychiatry, emerged from an analysis of data from 11,380 participants in the Australian Genetics of Depression Study. The research indicated that roughly 25% of individuals with depression met at least three of six criteria defining this circadian subtype.
Key characteristics of circadian depression include symptoms that fluctuate with the seasons, a delayed midpoint of sleep (typically between 2 and 4 a.m.), and a phenomenon known as 'social jet lag.' Social jet lag occurs when an individual's sleep midpoint significantly differs between workdays and non-working days, causing their sleep patterns to misalign with societal schedules.
Additional criteria identified for this subtype include an evening chronotype (being more active at night), sleeping longer than average when given the opportunity, and reporting significant morning tiredness. Previous research has suggested that evening chronotypes may be associated with an increased likelihood of depressive symptoms due to potential for poor decision-making and impulsive behavior later in the day.
The study also noted that individuals with circadian depression may experience more adverse side effects from traditional antidepressant medications and find these treatments less effective. Emiliana Tonini, the first author of the study, emphasized the importance of recognizing different depression subtypes to ensure patients receive the most effective treatments earlier.
Furthermore, the research linked circadian depression to a higher risk of weight gain during depressive episodes, as well as increased susceptibility to inflammatory and cardiovascular health issues, and neurodevelopmental disorders such as ADHD. Individuals with this subtype may also experience depression at an earlier age and report more severe symptoms, including mania, psychosis, and suicidality.
Given the ineffectiveness of conventional medications and the link to the body's internal clock, researchers are proposing treatments that specifically target the circadian rhythm. These may include light therapy and melatonin as potential therapeutic interventions for individuals diagnosed with circadian depression.