Enhanced recognition of facial expressions of disgust in opiate users receiving maintenance treatment

Is pain empathy associated with pain indices and trauma history? A comparison between patients receiving methadone maintenance treatment and healthy controls

BACKGROUND

To study whether pain empathy and theory of mind (ToM) are related to pain indices and trauma experience, we studied opioid users receiving methadone maintenance treatment (MMT), a population with a history of traumas and a high prevalence of chronic pain.

METHODS

MMT patients (n = 53), substance abuse-free, with no impaired cognition (Montreal Cognitive Assessment (MoCA) ≥24), were compared to healthy controls (HC) matched by age and gender (n = 66). All participants were assessed using Reading the Mind in the Eyes (RMET) for ToM, empathy (Interpersonal Reactivity Index [IRI], Empathy Quotient Scale for Adults [EQ60]), and Pain Empathy [PE task]). An algometer was used for pain pressure threshold, and supra-pain threshold was rated using a visual analog scale (VAS). Catastrophizing, McGill pain, Negative life events (NLE), and MoCA questionnaires were administered. Substance abuse was tested in the urine of MMT patients and self-reported by HC.

RESULTS

MMT, compared to HC, were less educated with more NLE and a lower RMET (logistic regression). Groups had comparable empathy and pain indices, except for higher supra-threshold VAS rating and catastrophizing in univariate analyses. Pain empathy (PE) correlated with NLE in HC, and in MMT, with catastrophizing, which correlated with NLE, perceived stress, and pain intensity. Higher empathy was observed in 18 participants with a history of sexual abuse (83.3 % belong to the MMT group).

CONCLUSIONS

Pain Empathy was found to be associated with personal suffering experience in both groups, as reflected by correlations with NLE in HC and with catastrophizing, which correlates with NLE, stress, and pain intensity, in MMT.

Emotional Expression on Social Media Support Forums for Substance Cessation: Observational Study of Text-Based Reddit Posts

BACKGROUND

Substance use disorder is characterized by distinct cognitive processes involved in emotion regulation as well as unique emotional experiences related to the relapsing cycle of drug use and recovery. Web-based communities and the posts they generate represent an unprecedented resource for studying subjective emotional experiences, capturing population types and sizes not typically available in the laboratory. Here, we mined text data from Reddit, a social media website that hosts discussions from pseudonymous users on specific topic forums, including forums for individuals who are trying to abstain from using drugs, to explore the putative specificity of the emotional experience of substance cessation.

OBJECTIVE

An important motivation for this study was to investigate transdiagnostic clues that could ultimately be used for mental health outreach. Specifically, we aimed to characterize the emotions associated with cessation of 3 major substances and compare them to emotional experiences reported in nonsubstance cessation posts, including on forums related to psychiatric conditions of high comorbidity with addiction.

METHODS

Raw text from 2 million posts made, respectively, in the fall of 2020 (discovery data set) and fall of 2019 (replication data set) were obtained from 394 forums hosted by Reddit through the application programming interface. We quantified emotion word frequencies in 3 substance cessation forums for alcohol, nicotine, and cannabis topic categories and performed comparisons with general forums. Emotion word frequencies were classified into distinct categories and represented as a multidimensional emotion vector for each forum. We further quantified the degree of emotional resemblance between different forums by computing cosine similarity on these vectorized representations. For substance cessation posts with self-reported time since last use, we explored changes in the use of emotion words as a function of abstinence duration.

RESULTS

Compared to posts from general forums, substance cessation posts showed more expressions of anxiety, disgust, pride, and gratitude words. "Anxiety" emotion words were attenuated for abstinence durations >100 days compared to shorter durations (t12=3.08, 2-tailed; P=.001). The cosine similarity analysis identified an emotion profile preferentially expressed in the cessation posts across substances, with lesser but still prominent similarities to posts about social anxiety and attention-deficit/hyperactivity disorder. These results were replicated in the 2019 (pre-COVID-19) data and were distinct from control analyses using nonemotion words.

CONCLUSIONS

We identified a unique subjective experience phenotype of emotions associated with the cessation of 3 major substances, replicable across 2 time periods, with changes as a function of abstinence duration. Although to a lesser extent, this phenotype also quantifiably resembled the emotion phenomenology of other relevant subjective experiences (social anxiety and attention-deficit/hyperactivity disorder). Taken together, these transdiagnostic results suggest a novel approach for the future identification of at-risk populations, allowing for the development and deployment of specific and timely interventions.

Social Cognition in Opioid Use Disorder

Background: Opioid use disorder (OUD) is associated with significant functional impairment and neurocognitive dysfunction, but only a handful of studies have investigated social cognitive abilities in this condition. This study aimed to investigate facial emotion recognition accuracy/biases and two different aspects of theory of mind (ToM) (ToM-decoding vs ToM-reasoning) in people with recovered OUD. Methods: The participants included 32 people with recovered OUD who were on Buprenorphine + Naloxone (B/N) maintenance treatment and 32 healthy controls. In addition to neurocognitive tasks, both groups were assessed by a facial emotion recognition task, the faux pas recognition task, and the reading the mind from the eyes task. Results: In comparison to healthy controls, people on B/N maintenance treatment showed deficits in facial emotion recognition (d = 1.32) and both aspects of ToM (d = 0.87-1.21). In analyses of individual emotions, people on B/N maintenance treatment had decreased accuracy in recognition of anger and fear and had a bias to identify other emotions as sad. The duration of opioid use was robustly associated with difficulties in the recognition of anger. Conclusion: People in B/N maintenance treatment have significant difficulties in recognizing the emotions and mental states of others. Deficits in social cognition might be important for understanding the difficulties in interpersonal and social functioning in people with OUD.

Decoding Emotion in Drug Abusers: Evidence for Face and Body Emotion Recognition and for Disgust Emotion

Background: Different drugs damage the frontal cortices, particularly the prefrontal areas involved in both emotional and cognitive functions, with a consequence of decoding emotion deficits for people with substance abuse. The present study aimed to explore the cognitive impairments in drug abusers through facial, body and disgust emotion recognition, expanding the investigation of emotions processing, measuring accuracy and response velocity. Methods: We enrolled 13 addicted to cocaine and 12 alcohol patients attending treatment services in Italy, comparing them with 33 matched controls. Facial emotion and body posture recognition tasks, a disgust rating task and the Barrat Impulsivity Scale were included in the experimental assessment. Results: We found that emotional processes are differently influenced by cocaine and alcohol, suggesting that these substances impact diverse cerebral systems. Conclusions: Drug abusers seem to be less accurate on elaboration of facial, body and disgust emotions. Considering that the participants were not cognitively impaired, our data support the hypothesis that emotional impairments emerge independently from the damage of cognitive functions.

Impact of adolescent methamphetamine use on social cognition: A human-mice reverse translation study

BACKGROUND

Methamphetamine dependence is associated with social cognition deficits that may underpin negative social outcomes. However, there are considerable inter-individual differences in social cognition within people with methamphetamine dependence, with age of onset of methamphetamine use being a potential contributing factor.

MATERIALS AND METHODS

We conducted two sequential studies examining the link between age of onset of methamphetamine use (adolescence versus young adulthood) and performance in social cognition tests: (1) a human cross-sectional study in 95 participants with methamphetamine dependence varying in age of onset (38 with adolescent onset and 57 with adult onset) and 49 drug-naïve controls; (2) a mice study in which we tested the effects of methamphetamine exposure during adolescence versus young adulthood on social interaction and aggression, and their potential neurochemical substrates in the striatal dopaminergic system.

RESULTS

We initially showed that people with methamphetamine dependence who started use in adolescence had higher antisocial beliefs (p = 0.046, Cohen's d=0.42) and worse emotion recognition (p = 0.031, Cohen's d=0.44) than those who started use during adulthood. We reasoned that this could be due to either social cognition deficits leading to earlier onset of methamphetamine use, or methamphetamine-induced neuroadaptive effects specific to adolescence. Mice experiments showed that methamphetamine exposure during adolescence specifically decreased social investigation during social interaction and upregulated striatal tyrosine hydroxylase (p < 0.05, Bonferroni corrected). There was no evidence of adolescent-specific methamphetamine effects on aggression or other measures of dopaminergic function.

CONCLUSION

Together, translational findings demonstrate heightened sensitivity to methamphetamine effects on social cognition during adolescence.

Dysfunctional personality beliefs and emotion recognition in individuals with methamphetamine dependence

Previous studies have demonstrated that individuals with methamphetamine dependence have impaired emotion recognition. However, heterogeneity in results from these studies may indicate that individual factors such as personality beliefs moderate emotion recognition deficits. Thus, we aimed to examine the relationship between dimensional estimates of dysfunctional personality beliefs and facial emotion recognition in 86 Australian treatment seekers with methamphetamine dependence. Dysfunctional beliefs were measured using the Personality Beliefs Questionnaire, and emotion recognition was measured with the Ekman's Faces Test. We applied hierarchical regression analyses to test the relationship between beliefs and emotion recognition after accounting for the effects of intelligence. Results indicated that personality beliefs reflecting antisocial and paranoid schemas together accounted for a significant increase in the variance in fear recognition (higher levels of beliefs associated with poorer fear recognition). Further, high levels of passive-aggressive personality beliefs were associated with a tendency to misclassify faces as disgust. Our findings suggest that antisocial, paranoid, and passive-aggressive dysfunctional personality beliefs may underlie inter-individual differences in emotion recognition in methamphetamine dependent individuals. Additional research is required to better understand the relationship between personality and social processing biases, and investigate the direct impact these have on the significant psychosocial impairments present in individuals with methamphetamine dependence.

Social cognition impairments in long-term opiate users in treatment

BACKGROUND

Long-term opiate users experience pervasive social difficulties, but there has been surprisingly limited research focused on social-cognitive functioning in this population.

AIM

The aim of this study was to investigate whether three important aspects of social cognition (facial emotion recognition, theory of mind (ToM) and rapid facial mimicry) differ between long-term opiate users and healthy controls.

METHODS

The participants were 25 long-term opiate users who were enrolled in opiate substitution programmes, and 25 healthy controls. Facial emotion recognition accuracy was indexed by responses to 60 photographs of faces depicting the six basic emotions (happiness, sadness, anger, fear, surprise and disgust). ToM was assessed using the Reading the Mind in the Eyes task, which requires participants to infer mental states of others from partial facial cues. Rapid facial mimicry was assessed by recording activity in the zygomaticus major and corrugator supercilii muscle regions while participants passively viewed images of happy and angry facial expressions.

RESULTS

Relative to the control group, the opiate user group exhibited deficits in both facial emotion recognition and ToM. Moreover, only control participants exhibited typical rapid facial mimicry responses to happy facial expressions.

CONCLUSIONS

These data indicate that long-term opiate users exhibit abnormalities in three distinct areas of social-cognitive processing, pointing to the need for additional work to establish how social-cognitive functioning relates to functional outcomes in this group. Such work may ultimately inform the development of interventions aimed at improving treatment outcomes for long-term opiate users.

Opioid system and human emotions

Emotions are states of vigilant readiness that guide human and animal behaviour during survival-salient situations. Categorical models of emotions posit neurally and physiologically distinct basic human emotions (anger, fear, disgust, happiness, sadness and surprise) that govern different survival functions. Opioid receptors are expressed abundantly in the mammalian emotion circuit, and the opioid system modulates a variety of functions related to arousal and motivation. Yet, its specific contribution to different basic emotions has remained poorly understood. Here, we review how the endogenous opioid system and particularly the μ receptor contribute to emotional processing in humans. Activation of the endogenous opioid system is consistently associated with both pleasant and unpleasant emotions. In general, exogenous opioid agonists facilitate approach-oriented emotions (anger, pleasure) and inhibit avoidance-oriented emotions (fear, sadness). Opioids also modulate social bonding and affiliative behaviour, and prolonged opioid abuse may render both social bonding and emotion recognition circuits dysfunctional. However, there is no clear evidence that the opioid system is able to affect the emotions associated with surprise and disgust. Taken together, the opioid systems contribute to a wide array of positive and negative emotions through their general ability to modulate the approach versus avoidance motivation associated with specific emotions. Because of the protective effects of opioid system-mediated prosociality and positive mood, the opioid system may constitute an important factor contributing to psychological and psychosomatic resilience.

LINKED ARTICLES

This article is part of a themed section on Emerging Areas of Opioid Pharmacology. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.14/issuetoc.

Predicting personality from network-based resting-state functional connectivity

Personality is associated with variation in all kinds of mental faculties, including affective, social, executive, and memory functioning. The intrinsic dynamics of neural networks underlying these mental functions are reflected in their functional connectivity at rest (RSFC). We, therefore, aimed to probe whether connectivity in functional networks allows predicting individual scores of the five-factor personality model and potential gender differences thereof. We assessed nine meta-analytically derived functional networks, representing social, affective, executive, and mnemonic systems. RSFC of all networks was computed in a sample of 210 males and 210 well-matched females and in a replication sample of 155 males and 155 females. Personality scores were predicted using relevance vector machine in both samples. Cross-validation prediction accuracy was defined as the correlation between true and predicted scores. RSFC within networks representing social, affective, mnemonic, and executive systems significantly predicted self-reported levels of Extraversion, Neuroticism, Agreeableness, and Openness. RSFC patterns of most networks, however, predicted personality traits only either in males or in females. Personality traits can be predicted by patterns of RSFC in specific functional brain networks, providing new insights into the neurobiology of personality. However, as most associations were gender-specific, RSFC-personality relations should not be considered independently of gender.

Drug effects on responses to emotional facial expressions: recent findings

Many psychoactive drugs increase social behavior and enhance social interactions, which may, in turn, increase their attractiveness to users. Although the psychological mechanisms by which drugs affect social behavior are not fully understood, there is some evidence that drugs alter the perception of emotions in others. Drugs can affect the ability to detect, attend to, and respond to emotional facial expressions, which in turn may influence their use in social settings. Either increased reactivity to positive expressions or decreased response to negative expressions may facilitate social interaction. This article reviews evidence that psychoactive drugs alter the processing of emotional facial expressions using subjective, behavioral, and physiological measures. The findings lay the groundwork for better understanding how drugs alter social processing and social behavior more generally.

Impaired emotion recognition is linked to alexithymia in heroin addicts

Several investigations document altered emotion processing in opiate addiction. Nevertheless, the origin of this phenomenon remains unclear. Here we examined the role of alexithymia in the ability (i.e., number of errors—accuracy and reaction times—RTs) of thirty-one heroin addicts and thirty-one healthy controls to detect several affective expressions. Results show generally lower accuracy and higher RTs in the recognition of facial expressions of emotions for patients, compared to controls. The hierarchical multivariate regression analysis shows that alexithymia might be responsible of the between groups difference with respect to the RTs in emotion detection. Overall, we provide new insights in the clinical interpretation of affective deficits in heroin addicts suggesting a role of alexithymia in their ability to recognize emotions.

The effects of alcohol on the recognition of facial expressions and microexpressions of emotion: enhanced recognition of disgust and contempt

OBJECTIVE

The study compared alcohol's effects on the recognition of briefly displayed facial expressions of emotion (so-called microexpressions) with expressions presented for a longer period.

METHOD

Using a repeated-measures design, we tested 18 participants three times (counterbalanced), after (i) a placebo drink, (ii) a low-to-moderate dose of alcohol (0.17 g/kg women; 0.20 g/kg men) and (iii) a moderate-to-high dose of alcohol (0.52 g/kg women; 0.60 g/kg men). On each session, participants were presented with stimuli representing six emotions (happiness, sadness, anger, fear, disgust and contempt) overlaid on a generic avatar in a six-alternative forced-choice paradigm. A neutral expression (1 s) preceded and followed a target expression presented for 200 ms (microexpressions) or 400 ms. Participants mouse clicked the correct answer.

RESULTS

The recognition of disgust was significantly better after the high dose of alcohol than after the low dose or placebo drinks at both durations of stimulus presentation. A similar profile of effects was found for the recognition of contempt. There were no effects on response latencies.

CONCLUSION

Alcohol can increase sensitivity to expressions of disgust and contempt. Such effects are not dependent on stimulus duration up to 400 ms and may reflect contextual modulation of alcohol's effects on emotion recognition.

In the face of threat: neural and endocrine correlates of impaired facial emotion recognition in cocaine dependence

The ability to recognize facial expressions of emotion in others is a cornerstone of human interaction. Selective impairments in the recognition of facial expressions of fear have frequently been reported in chronic cocaine users, but the nature of these impairments remains poorly understood. We used the multivariate method of partial least squares and structural magnetic resonance imaging to identify gray matter brain networks that underlie facial affect processing in both cocaine-dependent (n = 29) and healthy male volunteers (n = 29). We hypothesized that disruptions in neuroendocrine function in cocaine-dependent individuals would explain their impairments in fear recognition by modulating the relationship with the underlying gray matter networks. We found that cocaine-dependent individuals not only exhibited significant impairments in the recognition of fear, but also for facial expressions of anger. Although recognition accuracy of threatening expressions co-varied in all participants with distinctive gray matter networks implicated in fear and anger processing, in cocaine users it was less well predicted by these networks than in controls. The weaker brain-behavior relationships for threat processing were also mediated by distinctly different factors. Fear recognition impairments were influenced by variations in intelligence levels, whereas anger recognition impairments were associated with comorbid opiate dependence and related reduction in testosterone levels. We also observed an inverse relationship between testosterone levels and the duration of crack and opiate use. Our data provide novel insight into the neurobiological basis of abnormal threat processing in cocaine dependence, which may shed light on new opportunities facilitating the psychosocial integration of these patients.

Hostility and cigarette use: a comparison between smokers and nonsmokers in a matched sample of adolescents

INTRODUCTION

We examined the association between hostility-a personality trait reflective of negativity and cynicism toward others-and smoking in adolescents by measuring (a) several subcomponents of hostility, and (b) facial emotion processing ability, which has been previously linked to hostility.

METHODS

Participants (N = 241 aged 14-19) were 95 smokers and 95 demographically matched nonsmokers as well as 51 nonmatched smokers. All participants completed the Cook-Medley (C-M) hostility scale, which provides a general hostility score and 3 component scores (cynicism, hypersensitivity, and aggressive responding), and a facial emotion processing task. This task, designed to assess emotion recognition, requires quickly identifying the emotion of faces that gradually morph from neutral to high-intensity happy, angry, or fearful.

RESULTS

Independent sample t tests indicated that matched smokers scored significantly higher in cynicism and aggressive responding than nonsmokers. Among smokers, age of smoking onset was negatively correlated with general hostility and aggressive responding. All hostility scales were positively correlated with the intensity needed to recognize happy faces. Counterintuitively, smokers required a greater intensity to recognize angry faces than nonsmokers. No other relations between hostility/smoking status and facial emotion processing were observed.

CONCLUSIONS

Aspects of hostility, particularly aggressive responding, may be a risk factor for early onset smoking. Although hostile participants exhibited a deficiency in their ability to recognize happiness in facial pictures, these results did not translate to differences in smoking status. This study elucidates some of the complex interrelations between hostility, emotion processing, and adolescent smoking, which may have implications for teen smoking prevention.

Deficits in social perception in opioid maintenance patients, abstinent opioid users and non-opioid users

AIMS

This study aimed to compare emotion perception and social inference in opioid maintenance patients with abstinent ex-users and non-heroin-using controls, and determine whether any deficits in could be accounted for by cognitive deficits and/or risk factors for brain damage.

DESIGN

Case-control.

SETTING

Sydney, Australia.

PARTICIPANTS

A total of 125 maintenance patients (MAIN), 50 abstinent opiate users (ABST) and 50 matched controls (CON).

MEASUREMENTS

The Awareness of Social Inference Test (TASIT) was used to measure emotion perception and social inference. Measures were also taken of executive function, working memory, information processing speed, verbal/non-verbal learning and psychological distress.

FINDINGS

After adjusting for age, sex, pre-morbid IQ and psychological distress, the MAIN group was impaired relative to CON (β = -0.19, P < 0.05) and ABST (β = -0.19, P < 0.05) on emotion perception and relative to CON (β = -0.25, P < 0.001) and ABST (β = -0.24, P < 0.01) on social inference. In neither case did the CON and ABST groups differ. For both emotion perception (P < 0.001) and social inference (P < 0.001), pre-morbid IQ was a significant independent predictor. Cognitive function was a major predictor of poor emotion perception (β = -0.44, P < 0.001) and social inference (β = -0.48, P < 0.001). Poor emotion recognition was also predicted by number of heroin overdoses (β = -0.14, P < 0.05). Neither time in treatment or type of maintenance medication (methadone or buprenorphine) were related to performance.

CONCLUSIONS

People in opioid maintenance treatment may have an impaired capacity for emotion perception and ability to make inferences about social situations.

Biased attention towards negative schematic expression in abstinent heroin abusers

BACKGROUND AND OBJECTIVES

Drug dependents exhibit biases when evaluating emotional facial expressions; however little is known about their emotional biases appearing at the pre-awareness stage. The present study examined whether abstinent heroin abusers preferentially attended to facial expressions with particular emotion type.

METHOD

Thirty-seven abstinent heroin abusers (AH participants), twenty normal healthy controls (NC participants), and nineteen individuals with moderate anxiety/depression disorders (PC participants) were included in the study. Participants searched displays containing a varying number of schematic neutral faces for a unique schematic face expressing either a positive or a negative emotion.

RESULTS

Results revealed that AH participants had generally shallower search slopes for locating the negative target face than those for locating the positive one, whereas no such difference was found on NC participants or PC participants.

CONCLUSION

It suggested that abstinent heroin abusers are biased to attend to negative expression more effectively than attend to positive expression. We proposed that this may result from abstinent heroin abusers' repeated exposure to people's negative expressions in their living environment or a pre-existing emotional processing deficit which could initiate the development of drug abuse behaviour.

Biased number perception of schematic expressions in abstinent heroin abusers compared to normal controls

BACKGROUND AND OBJECTIVES

Drug-dependent people exhibit biases when evaluating discrete emotional facial expressions. Little is known about how drug abusers process multiple expressions presented simultaneously. The present study investigated the number perception of schematic emotional expressions by abstinent heroin abusers.

METHODS

Eighty-four heroin abstainers with varied lengths of abstinence (short-term, mid-term, and long-term) and twenty healthy controls were examined. A method of limits was deployed to obtain estimates (points of subjective equality) of perceived numbers of schematic faces (expressing positive, neutral, or negative emotion).

RESULTS

Major results include the following: 1) heroin-abstinent participants showed significantly lower points of subjective equality for negative and neutral faces, but not for positive faces, compared to control participants; 2) heroin-abstinent participants showed lower points of subjective equality for negative faces and higher ones for positive faces when compared to neutral faces, while no such differences were found in control participants.

CONCLUSION

Heroin abusers demonstrate an exaggerated perception of number when exposed to negative expressions, even after a period of abstinence as long as 10 months. In addition, the current results could also reflect an underestimated perception of number during exposure to positive expressions and a heightened baseline for neutral expressions, or the attribution of negative valence to neutral expressions by heroin abusers.

Facial affect processing in patients receiving opioid treatment in palliative care: preferential processing of threat in pain catastrophizers

CONTEXT

As a multidimensional phenomenon, pain is influenced by various psychological factors. One such factor is catastrophizing, which is associated with higher pain intensity and emotional distress in cancer and noncancer pain. One possibility is that catastrophizing represents a general cognitive style that preferentially supports the processing of negative affective stimuli. Such preferential processing of threat--toward negative facial expressions, for example--is seen in emotional disorders and is sensitive to pharmacological treatment. Whether pharmacological (analgesic) treatment might also influence the processing of threat in pain patients is currently unclear.

OBJECTIVES

This study investigates the effects catastrophizing on processing of facial affect in those receiving an acute opioid dose.

METHODS

In a double-blind crossover design, the performance of 20 palliative care patients after their usual dose of immediate-release opioid was compared with their performance following matched-placebo administration on a facial affect recognition (i.e., speed and accuracy) and threat-pain estimation task (i.e., ratings of pain intensity). The influence of catastrophizing was examined by splitting the sample according to their score on the Pain Catastrophizing Scale (PCS).

RESULTS

Opioid administration had no effect on facial affect processing compared with placebo. However, the main finding was that enhanced processing of fear, sadness, and disgust was found only in patients who scored highly on the PCS. There was no difference in performance between the two PCS groups on the other emotions (i.e., happiness, surprise, and anger).

CONCLUSION

These findings suggest that catastrophizing is associated with an affective information-processing bias in patients with severe pain conditions.

Disgust as an adaptive system for disease avoidance behaviour

Disgust is an evolved psychological system for protecting organisms from infection through disease avoidant behaviour. This ‘behavioural immune system’, present in a diverse array of species, exhibits universal features that orchestrate hygienic behaviour in response to cues of risk of contact with pathogens. However, disgust is also a dynamic adaptive system. Individuals show variation in pathogen avoidance associated with psychological traits like having a neurotic personality, as well as a consequence of being in certain physiological states such as pregnancy or infancy. Three specialized learning mechanisms modify the disgust response: the Garcia effect, evaluative conditioning and the law of contagion. Hygiene behaviour is influenced at the group level through social learning heuristics such as ‘copy the frequent’. Finally, group hygiene is extended symbolically to cultural rules about purity and pollution, which create social separations and are enforced as manners. Cooperative hygiene endeavours such as sanitation also reduce pathogen prevalence. Our model allows us to integrate perspectives from psychology, ecology and cultural evolution with those of epidemiology and anthropology. Understanding the nature of disease avoidance psychology at all levels of human organization can inform the design of programmes to improve public health.

Pharmacological enhancement of drug cue extinction learning: translational challenges

Augmentation of cue exposure (extinction) therapy with cognitive-enhancing pharmacotherapy may constitute a rational strategy for the clinical management of drug relapse. While certain success has been reported for this form of therapy in anxiety disorders, in this paper we highlight several obstacles that may undermine the efficacy of exposure therapy for substance use disorders. We also review translational studies that have evaluated the facilitative effects of the cognitive enhancer D-cycloserine on extinction targeting drug-related cues. Finally, important considerations for the design and implementation of future studies evaluating exposure therapy combined with pharmacotherapy for substance use disorders are discussed.

An experimental study of aggressive and neutral interpretative bias in opiate-dependent and opiate-abstinent men

There is a paucity of research on the relationship between opiate use and aggression, and no previous study has examined this from a cognitive theoretical perspective, which views an individual's interpretation of information as a central mediator of their response to it. This study aimed to determine whether opiate users and ex-users differed from opiate-naïve controls on a task which involved processing ambiguous sentences. In an independent group design, the interpretative bias task was administered to 64 participants: 21 opiate-dependent receiving methadone maintenance treatment, 21 opiate-abstinent in rehabilitation, and 22 healthy unemployed controls. We found that both opiate-dependent and opiate-abstinent groups interpreted ambiguous sentences in a neutral rather than an aggressive way, whereas controls showed no bias in either direction. In the opiate-dependent group, neutral interpretative bias correlated both with their current dose of methadone and years of methadone use. These findings indicate that current and ex-opiate users in treatment have a bias towards neutral interpretations of ambiguous information. The fact that neutral interpretative bias in opiate-dependent individuals correlated with current dose and years of methadone use suggests that methadone treatment is associated with a neutral cognitive bias. Decreased testosterone levels associated with chronic opiate use may underpin this neutral bias.

A somatic marker theory of addiction

Similar to patients with ventromedial prefrontal cortex (VMPC) lesions, substance abusers show altered decision-making, characterized by a tendency to choose the immediate reward, at the expense of negative future consequences. The somatic marker model proposes that decision-making depends on neural substrates that regulate homeostasis, emotion and feeling. According to this model, there should be a link between alterations in processing emotions in substance abusers, and their impairments in decision-making. Growing evidence from neuroscientific studies indicate that core aspects of addiction may be explained in terms of abnormal emotional/homeostatic guidance of decision-making. Behavioral studies have revealed emotional processing and decision-making deficits in substance abusers. Neuroimaging studies have shown that altered decision-making in addiction is associated with abnormal functioning of a distributed neural network critical for the processing of emotional information, and the experience of "craving", including the VMPC, the amygdala, the striatum, the anterior cingulate cortex, and the insular/somato-sensory cortices, as well as non-specific neurotransmitter systems that modulate activities of neural processes involved in decision-making. The aim of this paper is to review this growing evidence, and to examine the extent to which these studies support a somatic marker theory of addiction. We conclude that there are at least two underlying types of dysfunction where emotional signals (somatic markers) turn in favor of immediate outcomes in addiction: (1) a hyperactivity in the amygdala or impulsive system, which exaggerates the rewarding impact of available incentives, and (2) hypoactivity in the prefrontal cortex or reflective system, which forecasts the long-term consequences of a given action.