A study in the British Journal of Psychiatry identified a potential new subtype of depression called "circadian depression," affecting about 23 percent of the more than 10,000 Australians with depression who participated in the research. People with circadian depression have an internal 24-hour clock that doesn't sync with their external environment, leading to disrupted sleep-wake cycles, low daytime activity, low energy, and weight gain during depressive episodes.
The condition isn't yet in the DSM-5, the diagnostic manual mental health professionals use, so it remains unofficial. However, researchers found that people with circadian depression tend to have more severe depression symptoms and are more likely to experience ADHD, anxiety, bipolar disorder, obesity, or insulin resistance.
Hillary Ammon, PsyD, clinical psychologist at the Center for Anxiety and Women's Emotional Wellness, explains that when the body's internal clock is misaligned, it disrupts the brain's coordinated changes throughout the day. "Increased tiredness, low motivation, or decreased focus can all be factors that lead to depression and also be traits of depression," Ammon says. The misalignment also affects metabolism and cortisol, the stress hormone. Elevated nighttime cortisol can increase anxiety and sleep difficulty, while metabolic changes can cause weight gain.
People with circadian depression showed poor responses to standard antidepressants like SSRIs or SNRIs. Aaron P. Brinen, PsyD, assistant professor of psychiatry and behavioral sciences at Vanderbilt University Medical Center, notes that sleep disruption and depression have a known connection. Since no set treatment exists yet, researchers suggest light therapy and melatonin may help reset the body's internal clock.
Brinen recommends that providers target the specific drivers of depression. "If it's being driven by sleep or sleep disruption, you're going to target that." He adds that people may need to be "more thoughtful about sleep, travel, and work schedules," prioritizing sleep the way someone with low blood sugar prioritizes eating.
If you're experiencing depression symptoms, talk with a mental health professional for evaluation and personalized treatment rather than self-diagnosing.