Peripheral Markers of Depression

Abstract

Major Depressive Disorder (MDD) is a leading cause of disability worldwide, creating a high medical and socioeconomic burden. There is a growing interest in the biological underpinnings of depression, which are reflected by altered levels of biological markers. Among others, enhanced inflammation has been reported in MDD, as reflected by increased concentrations of inflammatory markers—C-reactive protein, interleukin-6, tumor necrosis factor-α and soluble interleukin-2 receptor. Oxidative and nitrosative stress also plays a role in the pathophysiology of MDD. Notably, increased levels of lipid peroxidation markers are characteristic of MDD. Dysregulation of the stress axis, along with increased cortisol levels, have also been reported in MDD. Alterations in growth factors, with a significant decrease in brain-derived neurotrophic factor and an increase in fibroblast growth factor-2 and insulin-like growth factor-1 concentrations have also been found in MDD. Finally, kynurenine metabolites, increased glutamate and decreased total cholesterol also hold promise as reliable biomarkers for MDD. Research in the field of MDD biomarkers is hindered by insufficient understanding of MDD etiopathogenesis, substantial heterogeneity of the disorder, common co-morbidities and low specificity of biomarkers. The construction of biomarker panels and their evaluation with use of new technologies may have the potential to overcome the above mentioned obstacles.

Biological Markers in Anxiety Disorders

“…However, even though the diagnosis of anxiety disorders is still largely based on clinical symptoms, biomarkers could be a valuable tool to help identify individual patients with the disorder, improve treatment fit, and predict treatment responses. Such use of a biomarker is already common in other medical fields for various diseases such as asthma and rheumatoid arthritis [ 180 , 181 ], but detection of such a marker in psychiatric disease will be one of the most difficult tasks that researchers will ever face [ 182 ]. Identifying beneficial biomarkers can help diagnose and classify a group of psychiatric disorders.…”

Salivary Biomarkers of Stress, Anxiety and Depression

“…Research reports suggest that depression is the second most common disease in the world after heart failure and may even take the lead in 2030 [ 1 , 2 , 3 ]. Depressive disorders are very often preceded by the stress and accompanied by anxiety—the coexistence of anxiety and depression is found in nearly 75% of children and adolescents [ 3 , 4 ]. However, if anxiety and depressive disorders do not occur at the same time, they usually follow one another.…”

TPH2: A Key Gene Risk Factor and Potential Therapy Target in Depression

“…A mild depression episode manifests as sadness, anhedonia and a feeling of worthlessness, whereas Major depressive disorder (MDD) is classified by a recurring intention to commit suicide [12]. Suicidal tendency is exceedingly common among the people with MDD [13], almost half of which [14]. This tendency basically derives from a low sense of self-worth [15], making them disapprove of themselves and occasionally feel guilt.…”

“…Depression is a persistent and serious mental illness involving genetic, neurological and cognitive factors [1]. People with depression are often depressed, pessimistic, and even suicidal.…”