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You can’t have missed all the recent press about the possible role of inflammation in mental ill-health. Inflammation is increasingly billed as the root cause of a dizzying range of psychiatric conditions, from depression to addiction, anxiety to schizophrenia, obsessive compulsive disorder to autism.
It offers an exciting new way of thinking about mental health and treatments, but there is much yet to be worked out.
Inflammation is most familiar to us as part of the body’s normal immune response to a physical injury, infection or irritation.
In inflammation, blood flow is increased to a region, the permeability of local capillaries is increased to allow an easier exchange of fluids and proteins between damaged cells and blood, and white blood cells are released to attack invading micro-organisms. Inflammation thereby promotes recovery from infection or physical damage, and promotes healing.
What is fascinating is that inflammation in the body leads to psychological changes too.
In fact, inflammation affects neural systems and behavior in very specific ways, most notably by interfering with motivation, motor activity, arousal, anxiety and sensitivity to threat, as outlined by Andrew Millar - a Professor of Psychiatry and Behavioral Sciences at Emory University School of Medicine.
A short-term ‘sickness behavior’ in response to inflammation tends to make us lay low and conserve energy when we are injured or fighting an infection. It makes sense from an evolutionary point of view.
However, it is easy to see how chronic inflammation could underpin mental health disturbances through long-term effects on systems that signal reward, mediate threat and responses to it, or affect motivation.
In terms of mechanism, inflammation reduces levels of serotonin, dopamine and norepineprine in the brain, changes often correlated with mental illness. Furthermore, inflammation also reduces the production of BDNF, which is central to the creation of new neurons and synaptic connections, and critical to memory and flexible thinking.
Inflammation definitely appears to be an unexpected and very important piece of the mental health puzzle, but work on the precise link between inflammation and mental health disorders is ongoing. It is not a catch-all ‘smoking gun’.
Inflammation is likely to be a general risk factor that makes mental illness more likely: it is found at significantly higher levels on average in people with any mental illness.
The specific condition triggered—depression or anxiety or other—is determined by other factors such as life events and their timing, or genetics or preexisting tendencies. Thus it is possible to be generally inflamed, but mentally healthy, if someone is psychologically resilient.
Secondly, taking depression as an example, only about one third to a half of people with depression have raised inflammation levels, so inflammation cannot be "the cause" of depression (or anything else). At most, inflammation might be the cause of some depression, or a cause in combination with other factors for some depression.
So where does my dentist come in?
Periodontitis is one of the most common diseases—affecting nearly half of the US population—and causes an inflammation of the gums and the structures supporting the teeth.
Whilst the link between mental illness and poor dental health has been long established, it has historically been understood as related to the poor self-care and lifestyle often observed in those with poor mental health. Typically the finger has been pointed at negligent oral health care, poor diet, smoking, alcohol use and stress-induced changes in saliva.
However, it is now clear that inflammation can play a direct role in the development of mental illness, so there is a two-way relationship. As chronic gum disease (and other inflammatory conditions) lead to a significant and prolonged general increase in inflammatory markers throughout the body, treating them should give us a better chance for mental health.
So, yes: a trip to the dentist may improve your depression and general mental health!
‘OK, what does this mean for me?’
The key take-home message is that although inflammatory processes may not explain all mental illness, reducing inflammation where possible sounds like a pretty good investment for maintaining well-being, and for mental health recovery.
Manage specific causes of inflammation:
- Go and see the dentist!
- Review the management of any other inflammation-causing medical conditions (e.g. rheumatism and arthritis).
- Estrogen is protective against inflammation, therefore women in peri-menopause or menopause may particularly benefit from controlling inflammation.
- Consider losing weight if you are very overweight. Obesity is associated with increased levels of pro-inflammatory cytokines.
Interestingly, our familiar lifestyle foes—stress, poor diet, lack of sleep, low levels of exercise—can also lead to chronic inflammation. In fact, psychological stress is one of the most potent triggers for inflammation (possibly because of an evolutionary role in preparing the immune system for possible attack).
Pretty much whatever angle we take on mental health and illness, we are led inexorably back to the idea that lifestyle—that is, stress management, diet, good sleep and exercise—are the keys to mental health.
Manage general sources of inflammation:
- Can stress be reduced? Can life be made more manageable? Can stress-creating thoughts and beliefs be changed? Yoga, meditation and mindfulness increase parasympathetic tone, which inhibits inflammation.
- Eat a healthy diet, reducing inflammatory over-processed foods such as sugar, trans-fats, refined carbohydrates, alcohol and certain additives. (Be very skeptical of unproven fad diets and theories.)
- Poor sleep increases pro-inflammatory cytokines, which is yet another reason for improving sleep habits.
- Exercise. Just 20 minutes of moderate exercise can reduce inflammation.
Trauma and childhood adversity are also linked to higher levels of adult inflammation, possibly through changes in the hypothalamo-pituitary-adrenal axis and its effect on the immune system. Managing sources of inflammation, and learning better ways of coping to reduce stress can therefore be of particular benefit to those with a history of trauma.
We often behave as if improving our basic lifestyle is a "nice to have" but optional extra when we are trying to manage anxiety, depression, addiction or other difficulties. We’ll get around to it ‘once we’ve sorted out our problems’... But perhaps this is the wrong way round?
Changing ingrained lifestyle habits is hard, but with the right approach it can be done.
In sum, generalized inflammation in the body can trigger depression, and is associated with poor mental health. Treating inflammatory conditions such as gum disease reduces the inflammatory load on the body. So yes, dental treatment might help improve depression and general mental health.
Inflammation can also be reduced by improving the management of other inflammatory medical conditions, changing certain medications, and improvements to diet, exercise, stress and sleep; such changes would also aid mental well-being.
What do you think? Is your motivation to make positive changes helped by understanding the mechanisms through which they might help? Or are the barriers to change elsewhere?
