As early as the turn of the 20th century, clinicians observed patients with schizophrenia failing to respond to the pain of a myocardial infarction, ruptured appendix, or perforated bowel. Although this pain insensitivity in individuals with psychosis has been described in the literature for many years, the phenomenon is still poorly understood. We therefore reviewed the literature for findings concerning whether pain insensitivity in schizophrenia represents a state or a trait marker.
A comprehensive Medline search of the literature on pain insensitivity in subjects with schizophrenia was conducted.
While the literature contains anecdotal observations, case reports, and a few rigorous clinical studies concerning patients with schizophrenia being relatively indifferent to pain, there is a dearth of empirical, well-controlled studies in this area. Although early studies that examined the response of individuals with schizophrenia to thermal or electrical pain were constrained by a variety of methodological confounders, studies on this topic suggest that the higher pain thresholds observed in schizophrenia are best explained by a complex, multifactorial model. Most intriguing are the results of one recent study that found pain insensitivity in family members of persons with schizophrenia, suggesting that this phenomenon may be a trait or endophenotype rather than being due to a psychotic state.
Pain insensitivity in individuals with schizophrenia, which is associated with increased morbidity and mortality, is poorly understood. It is possible that pain insensitivity might serve as a prodromal predictor of susceptibility for schizophrenia. Future studies are needed to further clarify the neurobiology, pathophysiology, and practical clinical implications of this phenomenon.
"Previous experimental research (Potvin and Marchand, 2008; Levesque et al., 2012) demonstrated that people with schizophrenia have a diminished response to painful stimuli, including drug-naïve populations. This is concerning since pain insensitivity in schizophrenia is associated with increased morbidity and mortality (Singh et al. 2006). Considering these experimental results, it is probable that the prevalence of clinical pain established in our study is a substantial underestimate, especially considering the high number of physical comorbidities in patients with schizophrenia (Leucht et al., 2007; De Hert, 2011a, 2011b) and reports of low reporting (Kuritzsky et al., 1999) and help-seeking behaviours (De Hert, 2011b) and underutilization of appropriate medical care (Watson et al., 1981; de Almeidaa et al., 2013). "
[Show abstract][Hide abstract] ABSTRACT: Background:
People with schizophrenia frequently have physical comorbidities that can cause pain. Experimental studies report reduced pain sensitivity among schizophrenia patients, but it remains unclear if clinically relevant pain is less prevalent in schizophrenia.
We systematically searched major electronic databases from inception till 03/2014. Articles were included that reported the prevalence of clinical pain in people with schizophrenia. Two independent authors conducted searches, completed methodological quality assessment and extracted data. A random effects relative risks (RR) meta-analysis was conducted to determine the prevalence of all-cause and specific pain in schizophrenia, and the relative prevalence compared to the general population, and to assess moderators.
Altogether, 14 studies were included encompassing 242,703 individuals with schizophrenia (30.2-55.8 years) and 4,259,221 controls. Different types of pain were considered. The overall pooled prevalence of clinical pain in people with schizophrenia was 34.7% (95% CI=23.6-46.6). In the comparative analysis involving 7 studies with controls, the RR was 0.99 (95% CI=0.83-1.19). The pooled prevalence of headache among 94,043 individuals with schizophrenia was 29.9% (95% CI=3-69%) and the RR compared to 4,248,284 controls was 1.32 (95% CI=0.85-2.07). In moderator analyses, neither age, sex, study quality or pain assessment method influenced pain prevalence.
Clinical pain affects a third of people with schizophrenia and levels are similar with age- and sex-comparable controls. Future research is needed to determine if similar clinical pain prevalences in schizophrenia occur despite having more painful conditions, resulting from under-reporting, higher pain thresholds or lower help seeking behaviours.
Schizophrenia Research 12/2014; DOI:10.1016/j.schres.2014.10.017 · 3.92 Impact Factor
"Moreover, some studies showed that patients with Parkinson’s disease display a higher sensitivity to pain and greater brain responses to pain, which can be attenuated by an enhancement of dopaminergic neurotransmission , . In contrast, in patients with schizophrenia, an insensitivity to pain has been documented early  and confirmed in more recent experimental studies , . Further evidence for a dopaminergic influence on pain perception derives from observations of altered dopaminergic neurotransmission in various chronic pain conditions –. "
[Show abstract][Hide abstract] ABSTRACT: Pain is a multidimensional experience, which includes sensory, cognitive, and affective aspects. Converging lines of evidence indicate that dopaminergic neurotransmission plays an important role in human pain perception. However, the precise effects of dopamine on different aspects of pain perception remain to be elucidated. To address this question, we experimentally decreased dopaminergic neurotransmission in 22 healthy human subjects using Acute Phenylalanine and Tyrosine Depletion (APTD). During APTD and a control condition we applied brief painful laser stimuli to the hand, assessed different aspects of pain perception, and recorded electroencephalographic responses. APTD-induced decreases of cerebral dopaminergic activity did not influence sensory aspects of pain perception. In contrast, APTD yielded increases of pain unpleasantness. The increases of unpleasantness ratings positively correlated with effectiveness of APTD. Our finding of an influence of dopaminergic neurotransmission on affective but not sensory aspects of phasic pain suggests that analgesic effects of dopamine might be mediated by indirect effects on pain affect rather than by direct effects on ascending nociceptive signals. These findings contribute to our understanding of the complex relationship between dopamine and pain perception, which may play a role in various clinical pain states.
PLoS ONE 04/2014; 9(4):e96167. DOI:10.1371/journal.pone.0096167 · 3.23 Impact Factor
"Indeed, in samples of patients with chronic pain, there is a lower prevalence of individuals with schizophrenia as compared to people with other psychiatric disorders.26 However, patients with schizophrenia have a high risk of developing health problems and, with the exception of rates of suicides and accidents, they also have a life expectancy 20% lower than the general population.1 "
[Show abstract][Hide abstract] ABSTRACT: Patients with psychiatric problems show a tendency to develop temporomandibular disorders (TMD). Particularly, patients with schizophrenia are quite likely to have signs and symptoms of TMD due to the impairment of their oral health, the use of antipsychotic drugs, and other general health problems. In nonschizophrenic populations, TMD have been considered as the main cause of nondental pain in the orofacial region, involving mechanisms associated with changes in masticatory activity at the cortical and neuromuscular levels. Individuals with schizophrenia do not usually complain of pain, and TMD is misdiagnosed in this population. In this paper, we aimed to review the clinical aspects of TMD in people with schizophrenia on antipsychotic drug therapy.
Drug, Healthcare and Patient Safety 03/2014; 6(1):21-27. DOI:10.2147/DHPS.S57172
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