Circulating cytokine levels in the treatment of comorbid anxiety disorders

Levels of Peripheral Circulating IL-6 and IL-10 Decrease Over Time Despite High Depression Burden in PTSD Patients

BACKGROUND

Patients with combined depression symptoms and post-traumatic stress disorder (PTSD) often exhibit high levels of circulating inflammatory biomarkers as either a cause or consequence of their disease. We aimed to investigate how cytokines and depression symptoms develop with one-year follow-up and compare them with non-PTSD patients.

METHODS

The study had a longitudinal design with one-year follow-up measurements in an inpatient treatment setting at a psychiatric center in Norway. PTSD diagnoses were set using the Mini International Neuropsychiatric Interview (MINI). The first three measurements were at baseline (T₀), halfway (T₁) and at discharge (T₂) from a 12-week main stay, followed by a final measurement one year after discharge (T₃). Serum blood samples were collected on all four occasions. The Beck Depression Inventory-II (BDI-II) was administered at T₀, T₂ and T₃.

RESULTS

Levels of interleukin-6 (IL-6) and interleukin-10 (IL-10) in PTSD patients were higher than in patients without PTSD at T₀ (p = 0.005 and 0.042). The PTSD patients had a higher average level of IL-10 across all four measurements (B = 1.62, Standard Error (SE) = 0.78, p = 0.037). The IL-10 levels in PTSD patients declined from T₀ to T₃ (p = 0.039). The PTSD patients were more depressed than non-PTSD patients at T₃ (p = 0.019).

CONCLUSIONS

The levels of IL-10 and IL-6 in PTSD patients more closely resembled the levels in non-PTSD patients at one-year follow-up, despite level of depression being unchanged in the PTSD patients. This calls into question the close relationship between level of circulating cytokines and depressive symptoms, at least in PTSD patients. Further research is needed to investigate what appears to be a complex relationship between immune markers and depression in patients with PTSD.

Psychoneuroimmunology: The new frontier in suicide research

Elucidating complex, multifactorial phenomena like suicide and suicidal behaviors (SSB) require multidisciplinary fields such as Psychoneuroimmunology (PNI). Indeed, our appreciation of the bidirectional communication channels between the brain and the rest of the body with its immune arsenal as the key player has positioned PNI as a promising field of research. We now know that major psychiatric, behavioral, and somatic disorders related to SSB accompany neuroimmune dysregulation. These disorders range from depression, emotional dysregulation, atopy, and epilepsy to certain viral and parasitic infections. By utilizing epidemiological, genetic, microbial, and molecular approaches, the PNI research community has excogitated novel biomarker candidates and pathways in support of SSB risk stratification at individual level. This remarkable progress in just two previous decades shall, if successful, help implement personalized prevention and treatment strategies, using PNI-assisted tools. The aims of this narrative review and opinion piece are to summarize important discoveries concerning the role of neuroimmune activation in SSB and to highlight important future directions for the field. Major caveats of the findings concerning methodological approaches, clinical reality of frequent comorbid psychopathology, and novel molecular targets are presented. Finally, this review calls on the PNI research community for increased attention towards factors that promote resilience to suicide, while accepting "consciousness" under its wing. Thus, PNI represents the new frontier in suicide research. Future breakthroughs in this discipline shall bring us closer to understanding the biological substrates of qualia i.e., subjective, and experiential meanings of life and death.