The interdependent nature of physical health and mental health has been known for thousands of years, and the co-occurrence of mental and physical disorders in the same person is not uncommon in our society. In fact, studies from Singapore indicate that the number of individuals with both mental and physical disorders is on the rise from 5.8% in 2010 to 6.7% in 2016 as per the Singapore Mental Health Study.
The study also found depression to be the most common mental illness in Singapore among individuals with physical diseases. This is consistent with global data according to which depression is common among individuals suffering from various physical illnesses, including but not limited to diabetes, hypertension, arthritis, and cancer. Individuals with depression also have an increased occurrence of physical diseases such as diabetes, heart diseases, dementia, and cancer, among others.
In particular, depression is very strongly associated with diabetes; a 60% increased risk of diabetes is seen in people with a history of depression. The presence of diabetes also increases chances of depression, with as much as increasing the risk to two times in some cases.
One explanation of depression among individuals with diabetes is the psychological burden of life with diabetes and this burden is often associated with poor self-care behaviors. In addition, as per research studies, there are multiple other causes which can explain the high co-occurrence of depression and diabetes among individuals. See figure below, which explains common proposed mechanisms through which individuals can develop both the diseases.
- Dysregulation of stress response and other body processes
Biologically, stress is any stimulus that disrupts the body’s internal balance, i.e. physiological selfregulation. The response to stress includes a system of stress hormones and physiological changes which eventually aims to enable the individual to respond to the stressor through a ‘fight or flight’ response and eventually regulate the body back to balance.
In both, depression and type 2 diabetes, this stress response system becomes dysregulated leading to multiple other biological mechanisms which eventually lead to the development of both the diseases. - Immunity and Inflammation
Our inflammatory responses, as part of activation of innate immunity functions in response to specific genetic factors and outside adversity, are underlying triggers that lead to biological mechanisms for both depression and diabetes.
Common social stressors leading to the above two mechanisms:
Stressors during Adulthood and Adolescence
One of the social factors associated with both depression and diabetes is low socio-economic status (SES). Studies found that low-SES individuals had higher odds of being depressed and even higher odds of staying depressed. Relationship between deprivation and prevalence of diabetes has also been established with the prevalence of diabetes 1.6 times more in the most deprived category as compared to the least deprived category.
Social stressors in adolescence (10-19 years) also contribute to the mechanisms of these diseases, with stressors typically presenting themselves in form of depressive symptoms in the early stages.
Inequality for example, is known to result in social stress and the highly prevalent gender inequality makes the adolescent girls an especially vulnerable group. Adolescent girls reportedly face more stressful life events and have higher – almost double – rates of adolescent depression as compared to adolescent boys. Further, adolescent girls and boys also tend to struggle with social stress related to body image issues resulting in high levels of stress.
Adolescents who identify as sexual minority (lesbian, gay, bisexual, etc.) are also often at the receiving end of discrimination and are at risk for compromised physical and emotional health. Buildup of stressors over time, such as internalized homophobia, stigma consciousness, identity concealment, and experiencing heterosexism and victimization, makes such adolescents at a greater risk of health problems.
Adolescents growing up in poverty are also at risk of several negative outcomes, including poor academic achievement and violent behavior. Poverty often may be associated with limited community resources or a lack of parental monitoring and can lead to stressful circumstances.
Childhood Adversity
Childhood adversities such as parental mental illness, child abuse, neglect, etc. are also known to significantly contribute to symptomatology of both diabetes and depression. Alterations in stress responses have also been found in adult survivors of childhood abuse as compared to similar individuals without a history of abuse.
In-utero Stress and Nutrition
In-utero stress, i.e. stress experienced by fetuses while in the womb, as well as perinatal stress, can lead to permanent influences on the brain and behavior of the fetus / baby. Prenatal stress or anxiety is associated with raised basal cortisol or raised cortisol reactivity in the offspring.
Unhealthy Lifestyle
Unhealthy behaviors such as poor diet, low levels of physical activity, and smoking are also associated with both depression and diabetes. These unhealthy behaviors are known to result in dysregulation of stress response and body processes which are known mechanisms leading to both the illnesses. Depression is also linked to self-neglect and low self-esteem, which might increase risk of unhealthy lifestyles and, in turn, increase risk of diabetes.
