Understanding the circular relationship between physical and mental health

There is a growing realisation that mental illnesses may also, like other non-communicable diseases, be associated with metabolic ageing. Representational photo: SewCream / Shutterstock

The World Health Organization (WHO) defines mental health as “a state of mental well-being that enables people to cope with the stresses of life, realise their abilities, learn well and work well, and contribute to their community.” This conceptualization of mental health lies nested within the broader rubric of health as “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity”.

While the constitution of both the WHO as well as the Republic of India recognizes health as a fundamental right of the individual and the innate responsibility of the government; it is important to appreciate the determinants of our health for the right to healthcare to be duly comprehensive and effective.

Circular relationship between mental health and physical health
There is a growing discourse around mental health and a realisation of how fundamental it is to the health and well-being of the individual. This includes recognizing the circular relationship between our mental health and physical health. The triadic phenomenon of modernization, industrialization and urbanisation that has been underway in India since Independence has led to a decline in the occurrence of most communicable diseases, with improved mother and child mortality rates and a progressive increase in lifespans. This has been accompanied by demographic ageing, with about 20% of our population expected to be over 60 years of age by 2050, as reported by United Nations Population Fund, India (UNFPA) in its 2023 India Ageing Report.

This decline in communicable diseases has led to a corresponding increase in non-communicable diseases, especially cardiovascular diseases, cancers, chronic respiratory diseases and diabetes mellitus, accounting for over 60% of all deaths in India every year. One way to look at non-communicable diseases is as varying manifestations of a single underlying process – ageing. Ageing is associated with accumulating DNA damage, increased inflammatory damage and the progressive accumulation of free radicals within cells and tissues of the human body. This progressive increase in metabolic stress can manifest as alterations in our physical parameters – the most obvious of which is an increase in blood pressure, sugar and lipid levels with ageing.

How is this associated with our mental health?
There is a growing realisation that mental illnesses may also, like other non-communicable diseases, be associated with metabolic ageing. Mental illnesses have been shown to be associated with increased leakiness of the blood brain barrier, increased metabolic stress and higher levels of inflammation in the brain. Persons with mental illnesses tend to have altered metabolism of body sugars and higher levels of resistance to insulin. This leads to an increased risk of developing non-communicable diseases such as obesity, hypertension, diabetes mellitus and dyslipidemia (high cholesterol levels). This may be both cause and effect. In persons prone to mental illnesses, metabolism appears to be altered even before the onset of the symptoms of mental illness. However, mental illness is also associated with an increased tendency to be sedentary and lower levels of physical activity, which may also accelerate metabolic ageing. Over and above this, some medicines can contribute to weight gain and insulin resistance.

On the flip side, physical health can also affect mental health. Persons with chronic non-communicable diseases such as obesity, hypertension, diabetes mellitus and dyslipidemia are more prone to develop mental illnesses – in particular, depressive disorders and anxiety disorders. There are both biological and psychosocial reasons for this risk. The metabolic stress and increased inflammation associated with chronic non-communicable diseases can disrupt brain and blood function, increasing the risk of some mental illnesses. However, persons with chronic non-communicable diseases are also likely to have lower physical activity, poorer functioning in relationships and work, higher levels of disability, higher levels of chronic pain and chronic stress associated with both the experience of illness and the responsibility of disease management. These factors act to increase vulnerability to depressive disorders and anxiety disorders.

A fairly straightforward example of this circular relationship is the relationship between depressive disorders and heart disease. Patients with depressive disorders, especially if untreated, are two to three times more likely to develop heart attacks than those without depressive disorders. Also, patients who have had a recent heart attack are also two to three times more likely to develop depressive disorders than those who have not had a recent heart attack.

Similarly, about 40% of our risk of developing Alzheimer’s disease can be reduced by addressing 12 modifiable risk factors including: high blood pressure, physical inactivity, smoking, excessive alcohol consumption, air pollution, head injury, infrequent social contact, less education, obesity, hypertension, diabetes mellitus, depression and hearing impairment. Many of these risk factors are also shared with other chronic non-communicable diseases such as heart disease, cancer, diabetes mellitus and chronic respiratory diseases.

What does this mean for us? As is apparent, simple changes in our lifestyle such as a healthier diet, lower calorie consumption, higher levels of physical activity and reduced exposure to environmental pollution can lead to dramatically better physical and mental health over time. This is not merely the responsibility of the individual, but also that of communities, workplaces and governments to facilitate the creation of conditions that are conducive to a healthier lifestyle. The theme for World Mental Health Day on October 10th, this year, is “Mental Health is a Universal Human Right”. The emphasis is on improving knowledge, raising awareness and driving actions that promote and protect everyone’s mental health as a universal human right. Healthier lifestyles and better physical health are key to this realisation of mental health as a fundamental human right.

(Dr Migita M Dcruz is Associate Consultant, Department of Psychiatry and Behavioral Medicine, KIMSHEALTH)

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