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The overlooked relationship between clinical depression and other medical illnesses

The mental illness can significantly impact the course of medical treatment
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Dr. Joshua Rosenblat suggests that biological, psychological, and social factors are the main sources of depression among people with other medical illnesses. COURTESY OF TIM MOSSHOLDER/UNSPLASH
Dr. Joshua Rosenblat suggests that biological, psychological, and social factors are the main sources of depression among people with other medical illnesses. COURTESY OF TIM MOSSHOLDER/UNSPLASH

An overlooked issue in medicine is the high rate of depression among people with other medical illnesses, according to a recent paper by U of T-affiliated co-authors including Dr. Joshua Rosenblat, a clinician-scientist at the Department of Psychiatry, and Dr. Paul Kurdyak, the director of Health Systems Research at the Centre for Addiction and Mental Health.

They reviewed articles related to depression among people with other medical illnesses, a condition which is twice as common for them than in otherwise healthy patients. The Varsity spoke with Rosenblat to learn more about the high rates of depression observed in patients with other medical illnesses, and how to best tackle the issue.

Causes of depression in patients with other medical illnesses

Rosenblat suggested three main sources of depression among people with other medical illnesses: biological, psychological, and social. Psychological and social triggers can include sadness driven by unfortunate circumstances, such as a serious medical diagnosis.

When considering biological sources, Rosenblat said, “A lot of things… can happen in your body biologically that can actually have a profound impact on the immune and cognitive systems.”

Inflammation, often caused by infection, autoimmune disorders, and cardiovascular issues, can release inflammatory signals that lead to depression. This is likely an evolutionary adaptation meant to reduce the spread of disease disincentivizing socialization through depressive symptoms.

Additionally, neurological disorders can also make the brain more susceptible to depression. As an example, half of all stroke victims will develop depression.

Impacts of depression on treatment

It is important to note that while illness can cause depression, depression can also give rise to illness. For example, depression often leads to changes in appetite, resulting in malnourishment or complications related to overeating.

Additionally, just as inflammation can trigger depression, so too can depression trigger inflammation, leading to the development of autoimmune disorders among patients. Depression can also cause harmful changes in behaviour, such as alcohol or tobacco use disorders, which may lead to other illnesses such as cancer, and can worsen pre-existing medical conditions.

Depression can have serious impacts on disease recognition. According to Rosenblat, there is an increased risk of a false link between symptoms of neurological disorder or medical illness. For example, a patient with diagnosed anxiety may also have an undiagnosed stomach ulcer, but their stomach problems may be dismissed as a symptom of anxiety.

The opposite is also true: a patient being treated for cancer might struggle with low energy caused by undiagnosed depression, but this may be dismissed as a symptom of cancer.

Diagnosing and treating depression

Depression is often not properly diagnosed among people with other medical illnesses. It is difficult to measure how often depression is under diagnosed, but Rosenblat estimates at least 25 per cent of cases are not diagnosed.

There are a number of reasons for this discrepancy. Primarily, patients and medical providers may feel uncomfortable discussing depression. In addition, there may be problems with the systems used to diagnose depression. Screening tools that are too specific may overlook some patients who have depression, while screening tools that are too sensitive may overwhelm the mental health system with some patients who do not have depression.

An overwhelmed medical system can also mean that patients who have issues more serious than their depression might not have time to discuss depressive symptoms. Rosenblat suggested a number of solutions to these diagnosis problems, including reducing stigma, as well as pairing highly sensitive and highly specific screening tools.

An example of paired screening tools might be a doctor asking, “Do you feel depressed?” and “Do you feel less motivated?” as sensitive tools. If the responses are affirmative, they would follow up with a test that asks about symptoms of depression, which is a specific tool.

Unfortunately, screening improvements do not necessarily lead to improvements in depressive symptoms. Many hospitals do not have adequate resources to treat depression. More investment into the mental health system, as well as better treatment education for medical providers would help.

According to Rosenblat, the current recommended treatment includes starting with less intense interventions, such as community engagement and socialization, and if those do not work, trying antidepressants and psychotherapy.

Next steps for depression research

What’s on the horizon of depression research? A number of more radical treatments, such as psychedelics — Rosenblant’s current focus of research — and the dissociative anesthetic ketamine have shown interesting clinical trial results. More research is generally needed for biological treatments of depression.

Lastly, Rosenblat suggested that future clinical trials should begin with stronger predictions, such as the potential side effects of a drug and the ways in which it will improve depression. This is different from previous methods, which simply gave a drug to patients and considered side effects and biological pathways in hindsight.

Depression is difficult to both discuss and study. Numerous changes, such as reduced stigma, better funding, and additional research need to take place to improve the diagnosis and treatment of depression.

For now, the results of this study demonstrate the importance of considering depression among people with other medical illnesses and how to best go about diagnosing and treating the disease.

If you or someone you know is in distress, you can call:

  • Canada Suicide Prevention Service phone available 24/7 at 1-833-456-4566
  • Good 2 Talk Student Helpline at 1-866-925-5454
  • Ontario Mental Health Helpline at 1-866-531-2600
  • Gerstein Centre Crisis Line at 416-929-5200
  • U of T Health & Wellness Centre at 416-978-8030.