Published online Aug 19, 2020. doi: 10.5498/wjp.v10.i8.175
Peer-review started: February 29, 2020
First decision: April 29, 2020
Revised: May 31, 2020
Accepted: June 27, 2020
Article in press: June 27, 2020
Published online: August 19, 2020
Major depressive disorder (MDD) affects 350 million people, approximately 6% of whom are adolescents; however, research on this age group is limited. The depressive symptomatology in adolescents can be confused with other psychiatric disorders, in turn affecting the proper diagnosis and normal development of patients. MDD in adolescents is associated with several negative outcomes including other psychiatric disorders later in life, educational impairment, self-injury, and suicide.
The immune system reaches maturity at about 16 years of age and upon the central nervous system second neural pruning. This makes adolescent patients with MDD have molecular characteristics that initially differ from adults and the elderly. These particularities have not been efficiently explored.
This study determined the differences in circulatory levels of eotaxin, interleukin (IL)-8, interferon gamma-induced protein (IP)-10, monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein (MIP)-1α and MIP-1β in HVs and adolescents with MDD, and assessed the changes induced by antidepressants consumed during 8 wk of clinical follow-up, which is the minimum time to observe the therapeutic efficacy of selective serotonin reuptake inhibitors, like fluoxetine.
We measured serum levels of eotaxin, IL-8, IP-10, MCP-1, MIP-1α, and MIP-1β in adolescents with MDD and performed a clinical psychiatric evaluation using the Hamilton depresión rating scale (HDRS). Eighteen HVs and twenty-two adolescents with MDD were monitored throughout 8 wk of clinical follow-up.
All evaluated chemokines decreased at 4 wk, but only MCP-1 and IL-8 differed significantly (P < 0.05) between 0 and 4 wk. In adolescents with MDD, all chemokines rose to their initial concentrations by 8 wk (vs 0 wk), but only IP-10 did so significantly (P < 0.05). All patients experienced a significant decrease in HDRS scores at 4 wk (P < 0.0001) and 8 wk (P < 0.0001) compared with 0 wk. Despite the consumption of fluoxetine, adolescents with MDD had significantly higher chemokines levels, even after considering the improvement in the HDRS score.
Our results showed a significant elevation in serum chemokine levels in adolescents with MDD despite treatment with fluoxetine and an improvement in HDRS scores. This prompted us to consider the multidisciplinary management of MDD patients since high levels of MCP-1 and IP-10 are associated with coronary risk. The elevation detected in eotaxin, IP-10, and IL-8 serum levels might explain certain features of depressed patients such as impaired cognition, memory, and learning.
Given the number of functions in which chemokines and their receptors are involved in the central nervous system, they could become novel diagnostic markers or therapeutic targets for MDD patients. However, a more significant number of studies are required, particularly in the adolescent population.