What is pain Can pain be mental

When the pain doesn't hurt anymore

What happens in the body when people do not feel even the most severe injuries?
by Iris Klossika, Christian Schmahl and Martin Bohus

 

There are people who are pathologically hypersensitive to external stimuli. But there are also people who feel no pain even if they cut their skin deeply with razor blades. This self-harming behavior is typical of the "borderline disorder", a serious mental illness. A fundamental question arises for both over- and insensitivity to pain: What exactly has changed so much about the processing of pain in the body of the person affected that the normal mechanisms of pain perception are overridden? An answer to this question will help better understand not only the borderline disorder but also the pain.

Have you ever had the experience that dental treatment becomes even more painful if you are afraid of it? Or have you ever seen a football player continue playing immediately after a rough foul, as if nothing had happened? Almost everyone of us should know from everyday experience that the pain we feel does not only depend on the severity of an injury. In fact, thoughts, feelings and factors such as attention and stress influence the perception of pain at least as strongly as the objective pain stimulus, i.e. the information about the injury that is received via pain-specific receptors - so-called nociceptors.

Similar to other sensory perceptions, the perception of pain has its own sensory system of specific receptors, nerve tracts and networked brain centers: the "nociceptive system". The term nociception for pain processing goes back to the Latin word "noxa", which means "harm"; A harmful stimulus is technically referred to as a noxious agent. Nociceptors are specific in that they respond only to potentially damaging stimuli; different types of nociceptors react to mechanical and / or thermal stimuli, others to chemical stimuli. The perception of pain can be influenced in almost all stations of the nociceptive system.

In itself, the fact that pain perception can change depending on context is a normal and biologically meaningful phenomenon. However, it becomes problematic when a person's perception of pain changes permanently. This can be the case with various diseases. An example of a pathological hypersensitivity to pain is the fibromyalgia syndrome; In this pain disorder, the excessive sensitivity probably has mainly organic causes, but is still largely unexplained. In contrast, there are people who feel no pain even after making bleeding cuts to themselves with a razor blade. This phenomenon occurs particularly frequently in connection with what is known as borderline personality disorder. In both cases the question arises: What exactly has changed in the nociceptive system so much that the normal mechanisms of pain perception no longer work?

Borderline disorder is of particular interest in this context because it is a psychological disorder. In order to understand how such a disorder can lead to a change in pain perception - as far as this can be explained according to the current state of research - one must first know something about the basics of pain perception.
How the brain processes pain

There is no specific "pain center" in the brain. The processing of various aspects of the painful information - for example the type of stimulation, the intensity of the stimulus, the emotional response and the mental evaluation - takes place in a network of brain centers, even if these interact so strongly that it is difficult to clearly distinguish pain aspects from one another to delimit.

The first station of most of the pain-conducting nerve pathways that lead from the periphery of the body - such as the skin or intestines - into the brain is the thalamus. This structure of the midbrain is considered to be the "gate of consciousness" because it is there that almost all sensory impressions are interconnected and passed on to other brain regions. Already here the processing of the so-called somatosensory aspects of the pain perception is separated - to a certain extent the "objective" information such as the localization and the physical properties of the noxious stimulus - and the affective, i.e. emotional effects of the pain. The somatosensory pain aspects are interconnected in the lateral (outer) thalamic nuclei and passed on to the primary and secondary somatosensory cortex (SI and SII). Affective pain information is processed via medial (centrally located) thalamic nuclei in the anterior cingulate cortex (ACC), the insular cortex and the amygdala. A third aspect, which is downstream of the other two and has a retroactive effect on affective pain processing, includes the cognitive (mental) evaluation of the painful stimulus. Areas of the anterior cingulum are probably also involved in processing this cognitive pain component, as well as prefrontal areas, in particular the dorsolateral prefrontal cortex (DLPFC). At the end of this complex processing chain, including the interactions between the brain centers that process the various aspects of pain, there is the conscious overall sensation of pain.
Selfharming behaviour

Borderline personality disorder is a serious mental illness. Those affected have an extremely unstable emotional life and uncontrollable impulsive behavior. Many of them inflict harm on themselves; the most common is cutting open the skin with razor blades or other sharp objects. Suicide threats and attempts are also common; the suicide rate in borderline patients is around nine percent, in the general population, however, only around 0.015 percent.

This condition affects around one percent of the population. The diagnosis of a borderline personality disorder is made according to the current version of the "Diagnostic and Statistical Manual for Mental Disorders" (DSM-IV-TR) if at least five of the following criteria are met:
  • a desperate attempt to prevent actual or suspected abandonment;
  • very intense but unstable interpersonal relationships, in which there is often a rapid change between idealization and contempt for the caregiver;
  • Identity disorders (strong fluctuations in self-image or self-perception): the affected patients are often not sure who they really are or what characterizes them;
  • recurring impulsive actions with a self-damaging character, for example lawn on the highway or sexually dissolute behavior;
  • Suicide attempts or threats or self-harming behavior;
  • pronounced fluctuations in feeling;
  • a chronic feeling of emptiness;
  • the difficulty of controlling anger and anger;
  • Temporary stress-induced paranoid delusions or severe dissociative symptoms ("stepping away", inability to feel your own body).
Essentially, it is a profound disturbance of affect regulation, combined with a consistently high level of tension, which most of those affected experience as very stressful. It is now believed that chronic stress plays a decisive role in the development of this syndrome. The reason for this is the striking connections with traumatic experiences in the patient's history; Experiences of serious physical or sexual abuse are the rule rather than the exception. Many of those affected also suffer from post-traumatic stress disorder.

The most obvious indication that something is wrong with the pain perception of borderline patients is the self-harming behavior observed in around 70 to 80 percent of all borderline patients. During these episodes of self-harm, many patients report that they do not experience the pain associated with the injuries or that they are only slightly aware of it. At some point in the nociceptive system, the normal processing of pain must be disturbed here.

Changed pain perception

Research currently agrees that borderline patients tend to experience pain less intensely than healthy people. It is not only during the often trance-like states in which self-harm is carried out that the pain sensitivity of these patients is reduced; Experimental pain stimuli, for example heat or pressure stimuli applied by researchers, have a comparatively low effect. In a state of high tension, which borderline patients often experience as extremely uncomfortable, the sensitivity to pain is reduced even more. This may explain self-harming behaviors: at least some of the patients seem to try to end this uncomfortable state of tension and the inability to perceive pain in order to "feel themselves again". This assumption is also supported by the fact that one could demonstrate a clear connection between pain perception and subjective tension on the one hand and dissociative states on the other hand: the more pronounced these states - typical of borderline syndrome - were, the less sensitive the patients were versus the painful irritation.

You get closer to it if you use imaging studies to study brain activity in borderline patients while they are experiencing pain. Various studies work here with functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). Various methods can be used to specifically influence and thus separate the different components - sensory, affective and cognitive - of pain perception. Amazingly, the sensory pain component seems to be processed completely normally in borderline patients. In an EEG examination, in which the electrical reaction of the cerebral cortex to painful laser stimuli (laser-evoked potentials, LEPs), it could be shown that, despite significantly reduced subjective pain perception, the reaction of the brain regions that process sensory pain aspects (SI and SII), is at least as strong as in healthy subjects. Neither a calculation task that was supposed to test the influence of attention nor a spatial discrimination task had an influence on the result. The reduced pain perception in these patients is therefore probably not related to reduced pain-related attention. A change in the processing of the affective and / or cognitive aspects of the pain is more likely.

Results obtained with fMRI can also be interpreted in this sense. Apparently there is a characteristic pattern of brain activity in borderline patients with painful irritation that is not found in healthy subjects. This applies in particular to a strong activation of the dorsolateral prefrontal cortex in connection with a deactivation of the perigenual ACC and the amygdala. This finding could be the organic equivalent of a cognitive inhibition mechanism that reduces the affective pain components that are processed in the ACC and amygdala.

Borderline patients may not experience pain as intensely because their emotional response to pain is slowed down by some kind of mental control. But in order to be able to say that with certainty, one would need experimental investigations that specifically pursue this question.

Can the feeling of pain be specifically influenced?

Even if one can assume that the reduced pain perception in borderliners is related to cognitive and affective factors, this has not yet been conclusively clarified. It would therefore be interesting to specifically influence the thoughts and feelings that patients have about pain. This could have different effects than in healthy people. For example, one might assume that negative mood affects borderline patients differently than healthy subjects. Healthy individuals usually become more sensitive to pain stimuli when they are moderately negative; A state of so-called "stress-induced analgesia" only occurs when there are massive negative emotions and high levels of tension. This phenomenon of insensitivity to pain caused by stress became known for the first time through anecdotal reports from soldiers, who often state that they recognized serious wounds "in the heat of the moment" as not nearly as serious. Such a reaction makes biological sense because it ensures that the ability to act is maintained even under high stress - i.e. potentially in great danger.

But what happens if someone experiences increased tension without any external influences, as is the case with borderline patients? In this case, pain sensitivity may decrease as the mood worsens instead of increasing as in healthy people. If that is the case, one should be able to observe abnormalities in the pain network in the brain at the same time.

Another interesting question is whether it matters if someone suffers from post-traumatic stress disorder in addition to borderline personality disorder. Amygdala deactivation with a simultaneous reduction in pain sensitivity has also been found in patients with post-traumatic stress disorder; many sufferers have both diseases. Could the findings in border-line patients be related to this second disorder only? Other open questions concern, among other things, the influence of the severity of the borderline disorder and the fact whether the patients are currently injuring themselves or not.

However, one question that clinical research has to ask itself is the question of relevance. Borderline patients mainly have problems with their unstable emotional life, their often dangerous impulsive actions, and their suicidal tendencies. Is it really that crucial whether or not they feel pain in one way or another problematic self-harm? What significance does this detail have for the overall picture of this disease, perhaps even for therapy?

First of all, this topic is important for the basics of pain perception. By examining deviations from normal pain processing - this also applies to excessive pain sensitivity such as in fibromyalgia - one can gain important information about the normal process. One example of this is the search for genetic influences on pain perception. In this context, for example, the genetic encoding of the enzyme catechyl-O-methyl transferase (COMT) is of interest: the genetic variation of a single amino acid within this enzyme leads to considerable differences in its activity. This in turn has a measurable influence on the pain processing of the person concerned, both on the subjective pain perception and on the underlying neurobiological processes. Are there any connections between such genetic factors and changes in pain perception, such as those found in borderline patients, for example?

The question of whether the lack of sensitivity to pain in borderline patients is more or less directly related to the symptoms is of direct relevance to borderline research. The self-harming behavior may be reduced if pain is felt during the self-harm, because at least in some patients the self-harm serves to end an unpleasant analgesic state. In this context, it would be interesting to ask what effect a pharmacological treatment of reduced pain perception has on the symptoms. Conversely, one can ask oneself whether an improvement in the symptoms, for example through psychotherapy, also normalizes the noticeable pain perception.

There is no shortage of current questions that the topic of "pain perception in borderlines" is currently asking. It is a research area that offers many possibilities and, in addition to research into a serious illness, also makes a contribution to basic research.
 
Dr. Iris Klossika is a psychologist and has been a research assistant at the Clinic for Psychosomatics and Psychotherapeutic Medicine at the Central Institute for Mental Health (ZI) in Mannheim since January 2006. For several years she has been concerned with the question of what causes an altered perception of pain.
Priv.-Doz. Dr. Christian Schmahl (left) is the senior physician in charge and research coordinator at the same clinic. From 2000 to 2001 he was on a research stay at Yale University. His main research interests are in the area of ​​pain and emotion regulation.
Prof.In 2003, Martin Bohus (right) accepted the chair for Psychosomatic Medicine at the Medical Faculty Mannheim and heads the Clinic for Psychosomatics and Psychotherapy at the ZI Mannheim. His main focus is on experimental psychotherapy.
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