The brain is the central organ of stress and adaptation because it perceives what is threatening and determines a behavioural response that may include fighting, fleeing, vigilance, and anxiety toward possible danger. The brain also determines health-damaging behaviours such as eating too much, smoking or drinking, and sleeping poorly. The brain regulates body processes through the nervous system, the neuroendocrine system, and the immune and metabolic systems, which work together as a nonlinear network that concurrently affects many body organs, such as heart, liver, kidneys and brain. The brain also responds to stress, sex, and metabolic hormones, which can alter neuronal architecture and alter behaviour as well as the regulation of those body processes.
For example, chronic stress, including sleep deprivation and jet lag, can produce changes in brain architecture, increase anxiety, alter mood, and decrease memory and cognitive flexibility. Fortunately, these changes in neuronal circuitry are reversible in a healthy, resilient brain. When they do not reverse after the stressor is removed, chronic anxiety and depression may occur that require treatment by behavioural and pharmaceutical means.
At the same time, with the epidemic of obesity and Type 2 diabetes, there is a new threat to the brain as well as to body health. Type 2 diabetes has damaging effects on the young brain as well as the adult brain. It impairs the capacity to learn and remember and has also been linked to increased risk for dementia. Thus counteractive measures, including diet and increased physical activity, are important for brain health as well as for body health.
The social environment has enormous impact on the individual through the brain. Besides major life events, abuse, and neglect, it is the ordinary day-to-day experiences in family, neighbourhood, school, and work that affect brain and body function and promote those health-damaging behaviours.
Socioeconomic status (SES), which includes both income and education, is a very strong predictor of brain and body health, even when health behaviours and access to health care are factored out. Gradients of both mortality and incidence of disorders of modern life such as cardiovascular and metabolic disease have been described in developed countries, where those with the least education and the lowest income have the highest disease incidence, on average, and those at the top have the lowest disease incidence and longer lives, on average. And there is a linear gradient, with people in the middle showing intermediate levels of life expectancy and disease frequency, which is why the middle class should also be concerned about these health-related issues.
Moreover, the very perceptions of inequality, in cities, states, and nations that have large differences between rich and poor have been linked to poorer physical and mental health for those who are not at the very top and a steeper gradient of cardiovascular, metabolic, and other diseases from low to high SES, as well as higher levels of depression, substance abuse, crime, and suicide, as has been documented in an number of recent publications.
[Dr. Neil] Perceptions of inequality is a key concept in brain health. In other words, understanding the drivers of “keeping up with Jones’” or more importantly, managing one’s own expectations in life – where you should be or what you should be achieving. The subconscious stress you place upon yourself has a far greater impact on the neuroendocrine system than anything physical.