Post No.: 0222
Comorbidity is the co-occurrence of one or more additional diseases or disorders with a primary disease or disorder of interest; or to simplify the definition for the purpose of this post – comorbidity is having multiple health issues of any kind that exist simultaneously, whether they’re related or seemingly independent from each other.
It shouldn’t be difficult to imagine that if you have cancer or have just become quadriplegic, for instance, how that will also affect your mental health. In fact, any type of major and stressful personal life event or change can increase the chances of experiencing mental health issues (including having a child or going through puberty or the menopause, even though these seem like non-unusual events in the course of people’s lives).
The comorbidity of depression and physical problems are two-way – depression can cause physical problems e.g. one can start to neglect one’s own diet and not feel like being physically active, or one can attempt self-medication and get physically hooked on drugs; and physical problems can also cause depression too e.g. viruses that affect the brain, stroke, a physical disability such as a chronic injury, chronic pain or the loss of a body part or function, leading to a loss of independence and self-worth. This means treating depression will likely help prevent other health problems, burdens and costs too.
Therefore it’s not as simple as thinking that depression sufferers aren’t economically worth treating, especially when accounting for ‘disability adjusted life years’ (DALYs), which are the total potential number of life years lost due to premature death and productive years lost due to disability. (Depression alone accounts for ~5% of all DALYs in the entire world.) There are thus financial as well as social costs, both personally and societally.
Likewise it shouldn’t be hard to understand again that if you’re chronically not feeling in a good mental frame of mind then you’re not going to be feeling physically energetic or optimal too, to do your best, most productive work or anything else. So don’t underestimate the risk of physical health problems co-occurring with any mental health problems.
As a result of comorbidity, there are therefore potential vicious circles that are hard to break. The stigma of depression can also add to the stress itself for sufferers. The symptoms of depression may not be as severe as e.g. schizophrenia, in general, but it’s far more common, can start relatively early in life and can last for many years. Along with the somatic (bodily) symptoms, the chronic duration (most of the day, nearly every day, for at least two or three weeks) of these symptoms are important to note, since everybody can temporarily feel any of the psychological (mind) symptoms without being clinically depressed.
A medical practitioner will, or should, therefore first need to rule out any other physical disorders that may be in turn causing or exacerbating the mental problems in a patient, where solving the physical health problem might subsequently solve the mental health problem too (e.g. treating the symptoms of a sufferer of HIV, which will enable the patient to feel better physically, which in turn will improve her/his mental state). Meow.
Comorbidity is common – even someone who has a phobia of going to the dentist can end up with bad teeth, who then eats an unhealthy diet full of soft processed foods and sugary drinks, who then becomes obese, who then becomes depressed and/or suffers from heart problems, and then who dies an early death, for instance. Thus seemingly trivial ‘non-life-threatening’ problems can matter down the line. It also demonstrates how bigger problems can be more effectively and more cost-effectively prevented, halted or treated if proactively nipped in the bud early (e.g. how good education and healthcare in childhood is vital, and should be considered a basic right – it’s a failure of society to not ensure these for all children). So don’t dismiss things just because they’re ‘not life threatening’ (yet) because that’s incredibly short-sighted.
Modern lifestyles have increased the prevalence of obesity, diabetes, heart disease and cancers (although longer life expectancies contribute to more cases of cancer too, along with e.g. obesity or pollution, since the longer people live, the more chances of them accumulating harmful cell mutations i.e. cancer, but I suppose greater average life expectancies is still precisely a product of modern medicine in the modern world), and these conditions themselves drive an increase in mental ill health. The increased accessibility and consumption of alcohol (low price and increased marketing) also drives alcohol misuse disorders. Rapid urbanisation in low and middle-income countries, and uprooting from a rural environment to a city, can have a huge impact on people’s mental health, possibility due to people losing their close-knit communities? Job insecurity in a globalised industrial world where one’s job can be done cheaper elsewhere or done by robots/computers increases anxiety. And vast inequities between the richest and the rest, and social comparisons and lower self-esteem due to mainstream and social media-perpetuated cultures of vanity and online abuse, also likely contribute to the increasing number of mental ill health cases across the world, in all parts of the world.
Non-communicable diseases (diseases that are not transmissible directly from one person to another) seem to correlate highly with mental disorders (e.g. alcohol dependency can cause many non-communicable diseases such as liver disease, or depression can indirectly lead to hypertension, diabetes or obesity) in both onset and severity. Unfortunately, having a mental health illness may make one less likely to seek treatment for a non-communicable disease, never mind seek help for the mental health illness itself, which can affect one’s chances of recovery for both – early intervention is often key to a swift and thorough recovery. Plus treatment tends to become more difficult for both problems if one has both a mental health disorder and a non-communicable disease.
New research is looking into whether some cases of depression are down to our immune systems attacking a healthy body and causing too much inflammation in the body and thus altering our mood. Inflammation and depression do go together (e.g. during an infection like a cold or flu, we do tend to feel less sociable, more withdrawn, irritable and tired, which are depression symptoms too). The chemicals in inflammation may therefore be directly affecting our mood? If true, this would again link to the knowledge that depression frequently co-occurs with some other disease or injury i.e. there’s a comorbidity. Life stressors and events, especially early in one’s life, may change our immune response – priming it to increase the risk of depression later in life. So anti-inflammatory drugs may help those who don’t respond to existing antidepressant drugs – a blood test can determine whether this kind of therapy is suitable for a sufferer. A link between gum disease and Alzheimer’s disease is currently being investigated too.
Whatever the case regarding what this research will find or confirm, there’s logically going to be some kind of underlying physical cause for a person’s depression because that’s how our bodies work at all levels – hence telling a depression sufferer to ‘snap out of it’ as if it’s a fluffy choice is as naïve and ignorant as telling a diabetes suffer to ‘snap out of your hypo/hyper’(!)
So viruses and autoimmune diseases can sometimes be the cause of some psychiatric disorders and so can confound diagnoses and therefore the appropriate treatments to prescribe to patients. Well it just reminds us that the body and mind are tightly or inherently interconnected – that problems with the wider body can affect the mind, and problems with the mind can affect the wider body (the brain is after all a subset of the body – not a separate or disconnected entity from the body altogether). From this understanding, disease comorbidities should really be expected rather than a surprise. Some cases of schizophrenia have been found to be actually down to autoimmune diseases and therefore require immuno-therapies rather than psychiatric treatments.
Growing research is also showing that the gut microbiome is linked to many different mental health conditions such as autism, depression and various subtypes of dementia – possibly due to a production of neurotransmitters that travel to the brain via the vagus nerve? The enteric nervous system (a part of the gut) is sometimes referred to as the ‘second brain’ for its density of neurons (although it’s not enough to simply have neurons to call something technically a brain). All this points to promising research into altering people’s diets and ultimately gut microbiota in treating or even curing some cases of mental disorders (psychobiotics).
Research is again relatively early at this moment but pollution is also being investigated to see if it is increasing the risk of psychosis.
As we begin to understand more and more about comorbidity and how the body and mind are intrinsically connected, we’re also understanding how we can improve the mind by improving the body, and vice-versa. Rather than all this research causing alarm that ‘everything’ can potentially increase the risk of mental health problems, this research bodes well for the future of mental health treatment and care because ‘everything’ can potentially be done to prevent or treat them too.
And because of the comorbidity risks of diseases and disorders – investing in the prevention, diagnosis and (early) treatment of mental and physical health problems will lead to public cost savings down the line, if we’re long-term rational enough.