The Complex Link between Inflammation and Depression

Dear Colleagues,

Depression is one of the most prevalent disorders worldwide, representing a heavy medical and social burden for many welfare systems. There are several forms of depression, ranging from mild to severe, based on the psychological domains impaired and on how much it affects every-day life. Major depressive disorder (MDD) represents the most severe stage in this range, with many milder and subclinical forms going undetected, especially in population strata with lower socioeconomic status and reduced access to healthcare service. Depression is comorbid with a number of chronic health conditions, such as cardiovascular disease (CVD), cancer, and diabetes, alongside a number of neuropsychiatric disorders. Depression represents a risk factor for these conditions, although in most cases it may be also a consequence. Moreover, depression often represents one of the first symptoms of common neurodegenerative disorders like Alzheimer’s and Parkinson’s disease. Common biological pathways like low-grade inflammation have been suggested to be at the basis of these links, and to be one of the pathological mechanisms acting in depression. However, many open questions remain in this field, and some aspects of the disease are still scarcely investigated. These include:

• The directionality of the relation between psychological health and inflammation, which remains unclear: while some data support the hypothesis that inflammation predisposes to depression, others suggest the opposite or even a bi-directional effect between depression and inflammation;
• A fine-grained picture of the relation between inflammation and specific depressive domains;
• The influence of lifestyle (e.g., nutrition) and other environmental exposures (e.g., pollution) on the link between depression and inflammation;
• The contribution of inflammation to treatment-resistant forms of depression and the effect of anti-depressant drugs on inflammatory response;
• The role of different biomarkers of low-grade inflammation in explaining the link between depression and chronic conditions like CVD, cancer, and type 2 diabetes;
• The long-hypothesized but yet unclear link between depression and platelets, which represent a sort of “circulating neurons”;
• The mechanisms which may explain why depression occurs in the prodromal phase of common neurodegenerative disorders;
• The role of inflammation in psychiatric comorbidities of depression and related traits, such as bipolar disorder, anxiety, suicidality, schizophrenia, and attention deficit hyperactivity disorder (ADHD).

Epidemiological, functional, and genetic/genomic studies attempting to clarify one or more of these aspects are invited to contribute to this Special Issue. Moreover, studies investigating measures and domains related to both depression and inflammation (e.g., association with frailty measures, cognitive performance, or other mental health scales like psychological resilience and quality of life) will be also taken into consideration. Studies using machine learning techniques and bioinformatic tools will be considered a plus, such as those investigating these relations in different ethnicities/ancestries, specific population strata (e.g., elders), or analyzing gender-specific aspects. Reviews on any of the abovementioned topics are also welcome.

Dr. Alessandro Gialluisi
Guest Editor

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• inflammation
• depression
• major depressive disorder
• depressive symptoms
• neuropsychiatric disorders
• neurodegenerative disorders
• cardiovascular disease
• diabetes
• cancer
• aging
• gender
• Parkinson’s disease
• Alzheimer’s disease
• anxiety
• bipolar disorder
• blood platelets