Depression Signs and Symptoms

• Depression can be defined as:
  • Mood state indicating the absence of a positive affect or the feeling of sadness, despair, anxiety, discouragement or hopelessness
  • Syndrome (eg major depression, minor depression or dysthymia)
  • Mental disorder wherein depression is a manifestation (eg unipolar major depression, bipolar disorder, schizophrenia)

Epidemiology

• According to the World Health Organization (WHO), depression is estimated to affect 5% of adults globally and is a leading cause of disability
  • Approximately 5.7% among adults >60 years are affected
• Depression is also a major contributor to the overall global burden of disease and can result in poor functioning of an individual in various areas such as work, school and family life
• Approximately 75% of affected individuals in low- and middle-income countries receive no treatment due to lack of resources, lack of trained healthcare providers and social stigma associated with mental disorders

• Patients may not present with depressive mood; somatic complaints may predominateDepression should be suspected in patients who present with physical symptoms (eg fatigue, gastrointestinal distress or back pain) which cannot be explained or in those who present with pain, anxiety or substance abusePresence of depressed mood or diminished interest or pleasure in activities (anhedonia), feeling of fatigue or lack of energy (anergia), significant loss of motivation (avolition) are essential in diagnosing depressionDiagnosis may be easier in patients who are more aware of their moods or functioning

• Involves multiple factors including genetic, environmental, social, psychological, and neurobiological factors
• It is believed to be related to changes in neurotransmitter levels in the brain, particularly the neurotransmitters glutamate, γ-aminobutyric acid (GABA), serotonin, dopamine, and norepinephrine
  • These neurotransmitters play a crucial role in regulating mood, emotion, and behavior
• Patients with depression have been observed to have problems involving the hypothalamic-pituitary-adrenal (HPA) axis (eg hypercortisolemia and decreased rhythmicity)
• Volumetric reductions in the hippocampus and other forebrain regions in patients with depression support the contribution of decreasing neurotrophic factors that regulate neuronal plasticity in depression
• Studies have also implicated the role of inflammation in depression
  • Treatment with antidepressants significantly decreased the levels of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), IL-10 and C-C motif ligand 2 chemokine
• Recent studies have also linked the microbiota-gut-brain axis to the regulation of mood, behavior and neuronal transmission, and its association with the development of depression
  • Gut microbiota can influence the brain through the HPA axis, neuroendocrine, autonomic and neuroimmune systems