Study identifies depression subtype related to biological clock

A recent study published in The British Journal of Psychiatry identified a subtype of depression associated with biological clock dysregulation. The research, part of the Australian Genetics of Depression Study, analyzed data from more than 10,000 participants with severe and recurrent depression ^1,2.

Circadian subtype characteristics

The researchers classified the participants into two groups: those with a 'circadian' subtype and those with a 'non-circadian' subtype of depression. To be considered circadian, the participant needed to present at least three characteristics associated with the biological clock, such as social jet lag, seasonality, delayed sleep midpoint, evening chronotype, morning fatigue, and hypersomnia. Approximately 23% of the participants were identified as having the circadian subtype ^1,2.

Individuals with circadian depression presented more severe symptoms, including (hypo)manic and psychotic experiences, suicidal ideation, psychological stress, and somatic complaints. They also reported weight gain during depressive episodes and a poorer response to selective serotonin reuptake inhibitors and serotonin and norepinephrine reuptake inhibitors, as well as more side effects compared to those with the non-circadian subtype ¹.