Differences in a person’s circadian rhythm — such as any changes in light exposure, motor activity and temperature cycles — may help in the diagnosis and treatment of depressive mood disorders, according to new research conducted by the Chronobiology Laboratory in Porto Alegre, Brazil.
The research suggests that these three cycles are disturbed in adults with depression and may play a role in the evaluation of clinical depression and perhaps even differentiate between acute and chronic depression.
Circadian theories have suggested that the circadian rhythm in patients with depression is out of alignment. Stable connections between internal rhythms, such as temperature and rest/activity, and the external day-night cycle are considered vital for adapting to life in the external world.
Maria Paz Hidalgo, M.D., Ph.D., and colleagues conducted the new study to investigate “chronodisruption” in people with depression. They also looked into whether the rhythm differences could differentiate between healthy individuals and patients with acute and chronic depression.
The study involved 30 women: 10 met criteria for a first depressive episode (never treated), 10 had major recurrent depression (taking antidepressants) and 10 were healthy, age-matched controls. None of the participants were jet-lagged or had performed shift work in the month before the study.
The rhythm variables — light, motor activity, and temperature — were continually assessed during a period of seven days.
The researchers found differences in rest/activity, peripheral temperature, and light intensity rhythms in depressed patients compared with healthy individuals. These variables may help differentiate between acute and chronic stages of depressive disorder.
With regard to the rest/activity rhythm, women having their first depressive episode and those with chronic depression showed a decrease in amplitude (smaller time difference between the peak and crest of the cycle) compared with the control group.
These differences were lower according to the severity of the illness, the researchers said.
“Because this variable was found to be a high coefficient for discriminating chronic depressive patients, it could be an important tool in clinical practice to evaluate the stage and prognosis of major depressive disorder,” said the researchers.
Depressed patients also showed lower amplitude in the circadian rhythm of light exposure, but a higher amplitude in the rhythm of temperature. Temperature remained above average for a longer time period in the depressive groups compared with the control group.
The researchers also found that the amplitude of the activity rhythm was capable of discriminating healthy individuals from acutely depressed patients.
Source: BMC Psychiatry