Many researchers over the years have suggested a strong link between people having mood disorders and people living with long-term (chronic) pains, however researchers still have no hard evidence to show why this is the case. Approximately 40% of people who are currently living with a chronic illness will experience depression in their life.
A recent study conducted on mice has found that chronic illnesses in mice can cause changes in the genetic make-up of parts of their brains that are known to be linked to mental issues such as anxiety and depression. The researchers investigated mice with damaged peripheral nervous systems to simulate chronic pain and what the researchers found was that the mice acted in ways very similar to humans with the same condition; they took extra measures to avoid anything that may cause them pain and they reacted very strongly to even the lightest of touches.
The group of researchers next looked at the activity of the genes in three specific areas of the mice brains that are known to be associated with anxiety and depression. The way that these areas are known to be related with those illnesses is via brain imaging. The three regions are: periaqueductal gray, its function is to act as a site of pain transmission; medial prefrontal cortex, its function is to mediate decision making and it is involved in the retrieval of remote long-term memories; nucleus accumbens, its function is to play a role in the reward circuit of an individual. After analysing these three areas, the team found approximately 40 genes that were acting vastly different to the same genes in a healthy mouse.
Before this investigation, the reason there may not have been a breakthrough is because these types of studies were only conducted for a week at a time. The successful study tested the mice for 10 weeks and this had an impact as at the start of their investigation they only witnessed small observations and a few symptoms, whereas nearing the end of their investigation they recorded much different behaviours.
If humans could comprehend the factors that are causing these changes to occur, it could lead to improved drugs for patients and us becoming less reliant on current anti-depressants which can take many weeks to effectively ease stress. The information gathered from this study is promising and provides a platform for people wanting to carry out further studies to stand on.