Looking back over the past year or so it's interesting to note the renewed interest in infection, and particularly inflammation, as a possible cause of depression. Recently, for example, some of the popular press has been spotlighting allergies. There's no particular evidence to prove that allergies cause depression but there is an association between those who suffer with allergies being at higher risk of depression. In fact allergy sufferers are twice as likely to suffer from depression. Take hay fever as an example. As any sufferer will know the effects often extend beyond dry eyes, sniffles and sneezes. They also include sleep disturbances, headaches and so on, which in turn affects mood. A family of proteins known as cytokines is of particular interest in this respect. Cytokines set off an inflammation response and may also reduce levels of serotonin in the brain - I'll come back to this in a moment - but allergy medications also carry side effects that include anxiety and mood disturbances, which blurs the picture somewhat in terms of causes and effects.
Everyone knows what it feels like to be ill. We feel drained of energy, incapable of moving from one place to another, and generally pretty wretched. Depression sufferers know these feelings only too except they have more symptoms besides. It has also been known for some time that cytokines and inflammation increases dramatically during episodes of depression. In fact by injecting an otherwise healthy volunteer with a substance that increases bodily inflammation for a short period of time we can readily observe increased anxiety and symptoms of depression.
Dr. Turhan Canli, a psychologist and associate professor in integrative neuroscience at Stony Brook University, New York, has been attributed as saying depression should be rebranded as an infectious, but not contagious, disease.
Aside from what you may feel about
'branding' any physical or mental condition, it's a bold claim which perhaps comes on the back of mounting evidence showing people with inflammatory diseases such as rheumatoid arthritis suffer more than most with depression. Inflammation isn't only caused by disease however. A high sugar and trans fat diet can be the cause as can obesity. Belly fat stores high quantities of cytokines and high stress levels are yet another cause of inflammation.
Some recent clinical trials have included anti-inflammatory medication with antidepressants and the results suggest an increase in response from those previously regarded as treatment resistant. Clearly there's a lot of work sitting in the in-tray so far as research is concerned. This isn't the first time we've looked at depression as a physical issue - the chemical imbalance theory is a case in point. Still, it's a worthy issue to investigate as any insight is better than none at all, and who knows what might be discovered as a result. As to how it may help, well some commentators suggest the stigma surrounding depression will lessen if it can be shown to be a physical illness. Let's see.