A new study supports a link between inflammation and depression and adds to the literature by associating inflammation with specific symptoms of depression, including sleep troubles and lack of energy and appetite.
Individuals with depression are known to have elevated levels of inflammatory markers, such as C-reactive protein (CRP), and it has recently been suggested that this association may be symptom specific, Markus Jokela, PhD, from the University of Helsinki, Finland, and colleagues note in a research letter published online November 18 in JAMA Psychiatry.
“Higher levels of inflammation are particularly likely to underlie depression symptoms that characterize sickness behavior, including fatigue, reduced appetite, withdrawal, and inhibited motivation. From an evolutionary perspective, such symptoms have the beneficial effect of preserving energy resources for use in fighting infection and promoting healing processes,” they say
Dr Jokela and colleagues tested the hypothesis that the association between CRP and depression is symptom-specific using data on roughly 15,000 men and women who participated in three US National Health and Nutrition Surveys. The mean age of the participants was 47.5 years, and the median CRP level was 2 mg/L (interquartile range, 0.8 - 4.7 mg/L).
“Inflammation was associated with a range of depression symptoms, particularly with tiredness, lack of energy, sleep problems, and changes in appetite,” the investigators report. These symptoms characterize sickness behaviors seen in people who are physically ill.