It’s becoming increasingly evident in the scientific community and among peer-reviewed literature, that inflammation is a large contributor of negative mood and risk factors for worsening depression [1,4,5,6]. So first of all, what is inflammation? Inflammation refers generally to increases in immune-system activation; swelling, redness, tenderness, heat and disturbed function. Imagine you receive a nasty cut or scratch on your arm, the area quickly becomes ‘inflamed’. Blood rich in immune cells are sent to the location to take care of any pathogens that may enter the body, preventing us from getting sick, or causing further damage.
This is a necessary and automatic response to real threats that can potentially damage the body, however, we can create unwanted inflammation through poor lifestyle choices, such as physical inactivity, unhealthy diet (high in processed foods, sugars, lack of fresh vegetables), smoking and alcohol consumption [1,4,5]. We can generate inflammation through our reaction of perceived or abstract threats (physical threats or stressful life circumstances [5]. Finally, visceral fat (the accumulation of fat around the central organs) is also known to secrete inflammatory messengers (cytokines) and assist in the development of depression or depressive symptoms [5].
Inflammatory cytokines, such as interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-α), and C-reactive protein (CRP) are some of the biomarkers for inflammation and are found in higher levels in approximately one third of patients with major depressive disorder (MDD) [5]. Cytokines signal the central nervous system to produce sickness behaviours, which are thought to facilitate an individual’s recovery from illness or injury and include symptoms such as anhedonia (lack of pleasure), fatigue and social withdrawal [6]. Interestingly, these symptoms are commonly found in people with depression. However, inflammation is not necessary or sufficient enough to induce depression entirely on its own, but they do play an important role in the development of depressive symptoms [4,5,6].
These cytokines produce depressive symptoms by altering the production, metabolism and transport of neurotransmitters that affect mood, including dopamine, glutamate and serotonin. Cytokines also produce oxidative stress that can negatively affect the mood and motivation areas of the brain, such as the prefrontal cortex and amygdala. On top of these already detrimental effects, increased cytokine levels leave us in stressed, worried and reactive states through the dysregulating effects on our “stress response system” of our brain, the hypothalamic-pituitary-adrenal (HPA) axis [4,5,6].
Now that we know the effects inflammation can play on our mood, how can we go about decreasing the number of cytokines we have running around causing a ruckus in our bodies and minds? First of all, reducing the factors discussed earlier by exercising, reducing excessive body fat, cutting smoking and poor lifestyle choices. A diet rich in vegetables, fibre and omega-3 is a fantastic way to reverse inflammation [1]. There are also a great number of foods with anti-inflammatory micronutrients which include turmeric, ginger, pepper and honey [2,3].
Remember, inflammation may not be the biggest enemy to some individuals when it comes to battling depression or improving mood, but if you recognised some of these factors/behaviours to be present in your lifestyle, you should consider reducing and altering them for a healthier body and mind!
References:
1. Galland, L (2010). Diet and Inflammation. Nutrition in Clinical Practice 25:6. 634-640
2. Ghosh, S; Banerjee, S; Sil, P (2015). The beneficial role of curcumin on inflammation, diabetes and neurodegenerative disease: A recent update. Food and Chemical Toxicology, 83. 111-124
3. Kafeshani, M (2015). Ginger, micro-inflammation and kidney disease. Nutrition, 31. 703-7
4. Kiecolt-Glaser, J; Derry, H; Fagundes, C; (2015). Inflammation: Depression Fans the Flames and Feasts on the Heat. American Journal of Psychiatry 172:11. 1075-1091
5. Slavich, G; Irwin, M; (2014). From Stress to Inflammation and Major Depressive Disorder: A Social Signal Transduction Theory of Depression. Psychological Bulletin. 774-815
6. Slavich, G; O’Donovan, A; Epel, E; Kemeny, M (2010). Black sheep get the blues: a psychobiological model of social rejection and depression. Neuroscience & Biobehavioral Reviews, 35(1), 39-45.
