Depression at the beginning of a year-long study of 3,200 patients raised
the likelihood of fatigue by four times, while fatigue at the start more
than doubled the chances of depression, says lead author Petros Skapinakis,
M.D., M.P.H., Ph.D., of the University of Ioannina School of Medicine in
Greece.
The study appears in the journal Psychosomatic Medicine.
Doctors have long been aware of the association between depression and
unexplained fatigue, but were never sure which symptom came first.
To find the answer, Skapinakis and two colleagues looked at patient data
from 14 countries, part of a World Health Organization study of psychological
problems in general health care.
“Fatigue and psychiatric disorder are not the same,” Skapinakis
says. “It is evident from the literature that fatigue and depression
have different risk factors.”
But they may have some overlap, too, he says. Fatigued persons might feel
psychologically distressed over their condition, and decreased energy is
one symptom of depression. Levels of physical activity could explain the
interaction between fatigue and depression, he says.
“Physical activity is known to have a protective effect on depression,” Skapinakis
says. “It has also been suggested that physical deconditioning
might be an important factor in the development of unexplained fatigue.”
Since treatment for both chronic fatigue and depression includes exercise,
future research might look at whether physical activity could explain the
interrelation of the two conditions.
