Interleukin 6 factors in sustained attention impairment in major depressive disorder
Patients with major depressive disorder (MDD) are more likely to have increased interleukin 6 (IL-6) levels and greater impairment of sustained attention compared with healthy individuals, a study has found. Abnormal IL-6 levels are implicated in sustained attention deficits in MDD.
The study included 30 adult patients with MDD and 30 healthy controls. Sustained attention was evaluated using the Rapid Visual Information Processing (RVP) task in the Cambridge Neuropsychological Tests Automated Battery. Serum IL-6 levels were measured using sandwich enzyme-linked immunosorbent assays.
Significant differences between MDD patients and controls were observed in the log10RVP total hits (p=0.017), log10RVP total misses (p<0.0001) and log10RVP mean latency (p<0.0001). Moreover, the serum levels of Log10IL-6 were significantly higher in the MDD group (p<0.0001).
Stepwise multivariate regression analysis revealed a significant association between log10IL-6 levels and the log10RVP mean latency among patients with MDD (p=0.025).
The findings indicate that abnormal levels of serum IL-6 may reflect an imbalance between pro- and anti-inflammatory mechanisms underlying the psychopathology of MDD, researchers said. Furthermore, IL-6 may play a vital role in the impairment of sustained attention in MDD.
However, researchers pointed out that the findings are preliminary given the relatively small sample size and absence of a longitudinal follow-up. More studies should therefore be conducted to confirm the data in a large and independent cohort of MDD patients.
It is not clearly known whether peripheral changes of IL-6 are directly related to the structural and functional changes of the brain, but recent reports point to a negative association between IL-6 levels and cognitive functions in patients with MDD. [Mol Psychiatry 2016;21;1696-1709]