Pain and Mental Health

Pain and mental health

Mixed Anxiety and depression are the most common mental health disorders in Britain, with about a third of the population experiencing some form of mental illness in the course of a year (Office for National Statistics, 2001). Mental illness refers to a range of mental health conditions that affect mood, behaviour and thinking (Gross, 2010). It is thought that these changes in mood will affect the perception of pain which will be investigated in this paper. The disorders that have been focused on are depression, schizophrenia and bipolar disorder. Although the majority of the studies that will be discussed have hypothesised that these mood disorders will  decrease the pain thresholds of those suffering, with their findings supporting the hypothesis, other studies have predicted the opposite and found an increase in the pain thresholds of those suffering from a mood disorder. The present paper will investigate both arguments, as well as discussing the reason behind there being such obvious variations in findings between studies in this area of research.

The gate control theory of pain may be the reason behind why mood influences pain perception. This theory introduced psychological causes for pain instead of just physiological causes, by claiming that a gate existed at the spinal cord which received input from peripheral nerve fibres and large and small fibres. The brain sends information related to a persons psychological state to the gate. This causes the gate to produce an output which sends information to an action system, thus resulting in the perception of pain. There are many factors suggested that result in the gate being opened or closed, with one of these factors being the individuals emotional state, i.e. anxiety, worry and depression will open the gate, creating an increase in perception of pain, whereas happiness, relaxation and optimism will close the gate reducing the perception of pain (Ogden, 2012). This theory gives a solid reason behind mood disorders affecting pain perception, with the following studies giving evidence for the the gate control theory.

Many studies have been conducted which show mood influences pain perception and pain influences mood. Evidence comes from Mel’nikova’s (1993) study where participants were asked to rate their pain and tolerate the pain for as long as they could. Mel’nikova found that participants who were depressed or anxious rated the painful stimulus as being more painful than the healthy participants did, despite the both groups being given the same stimulus. In a Similar study, pinerua-Shuhaibar et al (1999) found depressed patients tolerated acute pain for just under less than half the time than non-depressed participants (Morrison and Bennet, 2012). Both studies show that depressed participants will experience more pain than non-depressed participants, backing up the fact that mood affects pain perception. However, it can be argued that these studies and findings are outdated as views and knowledge about mental illness were extremely different compared to what they are today.

While there is evidence that depression will cause a lower pain tolerance in sufferers, little research has been done on chronic and acute pain sufferers in relation to mood and pain perception. Research has been done to explore how worry and anxiety relate to pain perception. Fordyce and steger (1979) looked into the relationship between anxiety and chronic and acute pain, and found that anxiety affects both types of pain in different ways. Pain increases anxiety in acute pain, but the treatment tends to be successful which decreases the pain and in turn, decreases the anxiety. This may be due to acute pain being easily treatable and the anxiety relates to this pain perception. However, because treatment has little affect on chronic pain, this increases anxiety which increases pain. Therefore, acute pain causes less anxiety due to the expectation that the pain will get better with the proper treatment but anxiety levels are higher in chronic pain because these disorders can’t be cured and medication is often ineffective. Again, this is a rather old study so may not be as relevant in today's society, but to later support the previous study mentioned, a more recent study conducted in 2008 found similar findings in relation to pain tolerances and perceptions. Research was done to investigate how mood has an affect on pain responses and pain tolerances in chronic back pain patients. Although this study is also aiming to find out the relationship between mood and pain, it is different to the previous studies mentioned as instead of using participants with naturally occurring depression, the researchers used a mood induction technique on participants to make them depressed, elated or neutral with the use of music to change their mood. Participants were asked to hold a heavy bag to create pain responses and tolerances on two occasions; once before they had received the mood induction and once after they had received the mood induction. This study found that those who had been given the depressed mood induction gave significantly higher pain ratings and had lower pain tolerances than those who received the elated and neutral mood induction. The depressed group held the bag for longer the first time before the mood induction than the second time. Therefore, the views expressed here would indicate that a depressed mood will increase pain ratings and lower pain tolerances. However, the mood induction method failed to work on some of the participants, which could be as a result of individual differences in music preference (Tang et al 2008).