Claudia Horn-Hofmann

The effect of nonrecurring alcohol administration on pain perception in humans: a systematic review.

Purpose Alcohol is believed to have pain-dampening effects and is often used as self-medication by persons with pain problems; however, experimental evidence confirming this effect is scarce. We conducted a systematic review of experimental studies on the effects of nonrecurring alcohol administration on pain perception in healthy human subjects and the underlying mechanisms. Method Three databases (PubMed, PsycINFO, and Web of Science) were searched for relevant studies using a predefined algorithm. In a next step, irrelevant articles were excluded by screening titles and abstracts. Finally, articles were checked regarding a set of methodological criteria; only publications meeting these criteria were selected for this review. A total of 14 experimental studies were identified. Results Overall, most of the studies were able to show a pain-dampening effect of alcohol. However, many of them had methodological shortcomings (eg, lack of placebo control, insufficient blinding, or very small sample sizes). In addition, comparability is limited due to considerable variations in alcohol administration and pain measurement. More importantly, potential mechanisms of action and moderating variables have scarcely been investigated. Conclusion Despite the frequent use of alcohol as self-medication by persons with pain problems, there are to date only a few experimental investigations of alcohol effects on pain perceptions. The results of these studies suggest that alcohol does in fact have pain-dampening effects. However, the mechanisms implicated in these effects are still unknown, and experimental research has been limited to pain-free subjects. Future research should provide more knowledge about alcohol effects on pain, especially in chronic pain patients.

Modulation of the startle reflex by heat pain: does threat play a role?

Previous studies have indicated that the startle reflex is potentiated by phasic, but not by tonic, heat pain, although the latter is seen as more strongly associated with emotional responses and more similar to clinical pain. The threat value of pain might be a decisive variable, which is not influenced alone by stimulus duration.

Psychological Predictors of Acute Postoperative Pain After Hysterectomy for Benign Causes

Objectives: Psychological parameters have been shown to contribute significantly to the development of acute postoperative pain (APOP). For the prediction of APOP in chest malformation patients and cancer patients, we found pain-specific psychological predictors to be of higher relevance than general psychological predictors. The current study aims to further substantiate these findings. Materials and Methods: In a sample of 73 middle-aged hysterectomy patients, 3 predictor sets were assessed 1 day before surgery: attentional biases (toward pain-related, social threat, and positive words in a dot-probe task), pain-related emotions and cognitions (pain anxiety, pain catastrophizing, and pain hypervigilance), and affective state variables (depression and somatization). APOP intensity rated 2 to 3 days after surgery and analgesic consumption during the first 48 postoperative hours were used as outcome measures. Results: APOP intensity ratings were significantly explained by their best single predictors in a multiple regression analysis: social threat words of the dot-probe task, pain anxiety, and somatization (14.7% of explained variance). When comparing standardized &bgr; coefficients, pain-specific psychological predictors appeared to be of higher explanatory relevance than general psychological predictors. In contrast, analgesic consumption could not be significantly predicted by the psychological variables. Discussion: Hysterectomy patients at risk for high APOP intensity could be characterized by the psychological variables used, whereas their predictive value for analgesic consumption was limited. The high predictive potency of pain-specific psychological variables should be considered for further improvement of pain management and prevention, because pain-specific variables such as pain anxiety can be the target of focal psychological interventions when preparing for surgery.

Prediction of persistent post-operative pain: Pain-specific psychological variables compared with acute post-operative pain and general psychological variables

Psychological variables and acute post‐operative pain are of proven relevance for the prediction of persistent post‐operative pain. We aimed at investigating whether pain‐specific psychological variables like pain catastrophizing add to the predictive power of acute pain and more general psychological variables like depression.

Associations of nocturnal sleep with experimental pain and pain catastrophizing in healthy volunteers

Strong alterations of night sleep (e.g., sleep deprivation, insomnia) have appeared to affect pain in inducing hyperalgesic changes. However, it has remained unclear whether everyday variations of night sleep in healthy individuals have any influence on pain processing. Forty healthy subjects were studied by portable polysomnography (PSG) and sleep questionnaire during two non-consecutive nights at home. Experimental pain parameters (pressure pain threshold, temporal summation = TS, conditioned pain modulation = CPM) and situational pain catastrophizing (Situational Catastrophizing Questionnaire = SCQ) were always assessed the evening before and the morning after sleep recording in a pain laboratory. Linear regression analyses were computed to test the prediction of overnight changes in pain by different sleep parameters. Significant prediction of changes in pain parameters by sleep parameters was limited (2 out of 12 analyses), indicating that everyday variations in sleep under non-pathological and low stress conditions are only weakly associated with pain.

The Relationship Between Pain Severity and Alcohol Use Among School-Aged Children and Adolescents: The Moderating Role of Drinking Motives

Objective Evidence from adult samples suggests a co-occurrence between pain and alcohol abuse. However, studies in adolescents are scarce and results are inconsistent, with some studies observing heightened and others observing reduced alcohol consumption in adolescents suffering from pain. We hypothesized that in adolescents the association between pain and alcohol use will be moderated by drinking motives. Methods Data from a large representative sample of Flemish school children and adolescents (N = 10,650, 50.8% boys, age range = 10-21 years, Mage = 14.33 years) were collected as part of the World Health Organization collaborative Health Behaviour in School-Aged Children (HBSC) survey. Pain severity was graded based on a pediatric pain classification system that accounts for both pain intensity and disability. Alcohol consumption was operationalized using two variables: frequency of drinking and drunkenness. The Drinking Motives Questionnaire-Revised was used to capture drinking motives; it assesses four motive categories (enhancement, coping, social, and conformity). Results Findings indicated that higher pain severity was associated with greater frequency of alcohol use and drunkenness. However, drinking motives moderated this association. The positive association between pain severity and drinking frequency was stronger in case of high conformity motives. Likewise, the association between pain severity and drunkenness frequency was stronger at high levels of conformity motives and reached significance only at high levels of coping motives. Conclusions Our findings suggest that specific drinking motives are linked to problematic alcohol use in adolescents with pain. Future studies using a longitudinal design are needed to draw conclusions about direction of effects.

Interactive effects of conditioned pain modulation and temporal summation of pain-the role of stimulus modality

Abstract Conditioned pain modulation (CPM) and temporal summation of pain (TSP) are 2 experimental paradigms capturing endogenous pain modulation, which have repeatedly demonstrated clinical relevance. Conditioned pain modulation describes the inhibition of the pain response to a test stimulus (Ts) when a second noxious stimulus, the conditioning stimulus (CS), is concurrently applied. Temporal summation of pain describes the enhanced pain response to a series of stimuli compared with single stimuli. Temporal summation of pain–limiting effects of CPM are likely but may depend on the stimulus modality of the Ts. This study aimed at investigating these differential effects of stimulus modality. Thirty-five healthy volunteers completed 2 experimental blocks (Ts modality: pressure vs heat) in balanced order. Both blocks consisted of 3 conditions: baseline (no CS), CPM1 (nonpainful CS: 42°C water bath), and CPM2 (painful CS: 46°C water bath). Single stimuli and series of stimuli were alternatingly applied to assess TSP by means of a Numerical Rating Scale. Both TSP and CPM were successfully induced with no difference between the 2 Ts modalities. We also detected a significant interaction between TSP and CPM, with higher pain reduction for a series of Ts compared with single Ts during the painful CS. Interestingly, this interaction was modality-dependent: TSP for heat Ts was completely abolished by CPM, whereas this was not the case for pressure Ts. Our findings suggest different forms of central sensitization induced by TSP using either heat or pressure stimuli, which differ in their susceptibility to CPM. Clinical implications and directions for future research are discussed.

Acute alcohol effects on facial expressions of emotions in social drinkers: a systematic review

Background As known from everyday experience and experimental research, alcohol modulates emotions. Particularly regarding social interaction, the effects of alcohol on the facial expression of emotion might be of relevance. However, these effects have not been systematically studied. We performed a systematic review on acute alcohol effects on social drinkers’ facial expressions of induced positive and negative emotions. Materials and methods With a predefined algorithm, we searched three electronic databases (PubMed, PsycInfo, and Web of Science) for studies conducted on social drinkers that used acute alcohol administration, emotion induction, and standardized methods to record facial expressions. We excluded those studies that failed common quality standards, and finally selected 13 investigations for this review. Results Overall, alcohol exerted effects on facial expressions of emotions in social drinkers. These effects were not generally disinhibiting, but varied depending on the valence of emotion and on social interaction. Being consumed within social groups, alcohol mostly influenced facial expressions of emotions in a socially desirable way, thus underscoring the view of alcohol as social lubricant. However, methodical differences regarding alcohol administration between the studies complicated comparability. Conclusion Our review highlighted the relevance of emotional valence and social-context factors for acute alcohol effects on social drinkers’ facial expressions of emotions. Future research should investigate how these alcohol effects influence the development of problematic drinking behavior in social drinkers.

Startle modulation by heat pain with varying threat levels in chronic pain patients and pain-free controls

Background Empirical evidence suggests that affective responses to pain are changed in chronic pain. The investigation of startle responses to pain might contribute to clarifying whether such alterations also expand to motivational defensive reactions. We aimed at comparing startle responses to tonic heat pain with high threat (HT) or low threat (LT) in patients with chronic musculoskeletal pain and controls. As pain-related anxiety and catastrophizing are typically elevated in chronic pain, we expected to find stronger startle responses in patients specifically under experimental HT. Methods Patients with chronic musculoskeletal, preferentially, back pain (N = 19) and matched pain-free controls (N = 19) underwent two pain-related threat conditions (high and low) in balanced order. Only, in the HT condition, 50% of the trials were announced to include a short further noxious temperature increase at the end. Startle responses to loud tones were always assessed prior to a potential temperature increase in the phase of anticipation and were recorded by surface electromyogram. Results Surprisingly, we observed no differences in startle responses and ratings of emotional and pain responses between patients and controls despite significantly higher pain-related anxiety and catastrophizing in the patients. Overall, startle was potentiated in the HT condition, but only in participants who started with this condition. Conclusion Our results suggest that, in general, patients with pain are not more responsive emotionally to experimental threat manipulations despite elevated pain anxiety and catastrophizing. Instead, exaggerated responses in patients might be triggered only by individual concerns relating to pain, which are not sufficiently mirrored by our threat paradigm.