Integrating mental & physical health: Towards a paradigm shift

Brain and mind: discrete or connected?

This approach has also been true of the body and mind, and, as a corollary, physical and mental conditions. Such a dichotomy evolved from diverse constructs: the historical concept of mind-body dualism¹, specialty-based categorization of diseases as either neurological or psychological, and the emphasis on objective diagnostic measures. However, contemporary understanding informs us that there are complex interactions between genetic risk, epigenetics, immune function and various environmental factors (exposome) that underlie brain and mind disorders. Thus, it emerges that psychiatric symptoms are common in many neurological conditions, including epilepsy, migraine, dementia, movement disorders, and stroke². Conversely, many neurological disorders are accompanied by psychiatric manifestations and epidemiological evidence often suggests a bidirectional relationship³.

Mental health, neurological health, and substance use conditions

The COVID-19 pandemic possibly brought to centre stage the complex interactions between mental health, neurological health, substance use (MNS) conditions and physical health in a way that caught global attention⁴. The World Health Organization has recently developed an integrated operational framework for mental health, brain health and substance use⁵. The central logic is the recognition of ‘a constellation of health conditions and disorders that compromise mental or brain health and functioning and may lead to cognitive, intellectual, psychosocial or physical impairment’. Common characteristics include shared determinants, common neural pathways, shared co-morbidities, as well as stigma and discrimination across these conditions.

Co-morbidity

Substance use disorders typically illustrate this complex interplay. The concept of alcohol related brain damage (ARBD) covers the plethora of structural and functional neuropathology associated with different levels of alcohol use⁶. Similarly, a wide range of psychiatric co-morbidity can accompany alcohol use⁷, with explanatory hypotheses including direct causal associations, shared genetic and environmental causes, as well as shared psychopathological characteristics. Substance use co-morbidity (misusing more than 1 substance) is often the norm, as illustrated by the co-occurrence of alcohol and tobacco use. A higher risk of infections, particularly HIV and Hepatitis, is well recognized among substance users⁸.

Co-morbidity increases adverse health outcomes both in terms of mortality, morbidity, and quality of life. Persons with schizophrenia who smoke tobacco die 10-15 yr prematurely as compared to the general population, with excess mortality arising from a non-communicable disorder (NCD), commonly respiratory or cardiovascular conditions⁹.

The chronic nature of severe mental illnesses like schizophrenia, necessitates the use of long-term anti-psychotic medications. This carries the risk of metabolic side-effects, such as weight gain and insulin resistance¹⁰.

Tobacco use has been linked with reduced medication effectiveness, increased mental illness relapse rates, and hospitalisation in this population¹¹. Further, the core symptoms of mental illness, which include lack of insight, might delay access to health care for co-occurring physical illness. There is also the high likelihood of diagnostic overshadowing, leading to neglect of concurrent physical problems, as primacy is given to the psychiatric condition.

The corollary is also well-established. Non-communicable disorders have a higher prevalence of psychiatric symptomatology. The pooled estimate from a meta-analysis of 96 studies in South Asian countries found a 40 per cent prevalence of depression in individuals with diabetes, 37 per cent in individuals with cancer, 38 per cent in those with hypertension, 39 per cent in those with stroke, and 44 per cent in individuals with COPD. The pooled prevalence of anxiety was 29 per cent in individuals with diabetes and cancer¹².

Multimorbidity

Co-morbidity refers to additional conditions that may be present alongside a primary one. Multi-morbidity refers to the co-occurrence of multiple chronic or acute diseases and medical conditions within one person, where one is not necessarily more central than the others¹³. A meta-analysis in 2023 suggests that 51 per cent of adults over 60 yr worldwide have multi-morbid conditions¹⁴. While multi-morbidity associated with ageing can be attributed to several biological hallmarks of ageing, multi-morbid conditions also exist in younger populations, including adolescents.

The growing understanding of the connections between various multi-morbid conditions suggests that these need be tackled together, addressing the conditions, as well as focusing on the promotion of health and well-being. Low levels of awareness and accessibility to services, as well as limited resources, merit an integrated approach which is rational, rights-based, adopts a biopsychosocial approach, focuses on health promotion, disease prevention, treatment, and recovery.

Public health principles of healthcare underlie all integrated approaches. These include ensuring that no one is left behind, special consideration for persons who are most vulnerable, gendered perspectives, adopting a life course approach, adapting interventions to local contexts, onboarding persons with lived experience, and ensuring inter-sectoral coordination beyond health sector interventions⁵.