It has recently been discovered that chronic, unpredictable, psychological stress in early life can lead to inflammation in the brain. This has come as something of a surprise to many researchers as it had previously been believed by most of those working in this recondite field of neurology that such inflammation of the brain had to have a physical (rather than psychological) cause such as a head injury or an infection.
According to McCarthy, an expert in this area of study, chronic and unpredictable stress in early life can cause particular brain cells (called microglia) to malfunction. This malfunctioning causes the microglia to produce neurochemicals that lead to neuroinflammation (i.e. inflammation of the brain).
What Is The Function Of Microglia?
Under normal circumstances (i.e. in a healthy brain) the function of microglia is to control the number of neurons needed by the cerebral cortex by ‘pruning away’ neurons that are superfluous to requirements.
What Happens When Microglia Malfunction?
However, when, due to chronic and unpredictable stress, the microglia malfunction, this may result in them going into a kind of destructive overdrive and the subsequent ‘pruning away’ of NECESSARY BRAIN CELLS THAT ARE VITAL TO EXECUTIVE BRAIN FUNCTIONING; this destructive process can lead to various neurological problems such as POOR IMPULSE CONTROL and IMPAIRED REASONING ABILITY.
Research also suggests that malfunctioning microglia may interfere with the generation of new neurons in the hippocampus and that this may be closely linked to the development of depressive disorders.
Depression, Microglia, And Animal Studies :
Indeed, the hypothesis that malfunctioning microglia may interfere with the generation of new neurons in the hippocampus which may, in turn, give rise to depressive disorders has been supported by studies of mice; when HEALTHY microglia are reintroduced into the brains of mice that have been induced into a depressive state their depressive symptoms ameliorate.
Implications For Treatment Of Depression In Humans :
However, more research needs to be conducted in order to discover what (if any) extent we can extrapolate from these studies in mice to help us develop similar ways of treating depression in humans.
McCarthy RC, Sosa JC, Gardeck AM, Baez AS, Lee CH, Wessling-Resnick M. Inflammation-induced iron transport and metabolism by brain microglia. J Biol Chem. 2018 May 18;293(20):7853-7863. doi: 10.1074/jbc.RA118.001949. Epub 2018 Apr 2. PMID: 29610275; PMCID: PMC5961037.