Angela S. Attwood

Association of the 5-HTTLPR genotype and unipolar depression: a meta-analysis

BACKGROUND We sought to ascertain the strength of evidence for association between the 5-HTTLPR polymorphism and unipolar depression. METHOD We applied meta-analytic techniques to data from relevant published studies, and obtained an estimate of the likely magnitude of effect of any association. We also tested for possible publication bias, and explored the impact of various study design characteristics on the magnitude of the observed effect size. RESULTS Meta-analysis indicated evidence of a small but statistically significant association between the 5-HTTLPR polymorphism and unipolar depression [odds ratio (OR) 1.08, 95% confidence interval (CI) 1.03-1.12]. This remained significant when data from samples of European and East Asian ancestry were analyzed separately. In all cases there was evidence of significant between-study heterogeneity, although the observed associations were robust to the application of a random-effects framework. CONCLUSIONS Our results support the presence of a small effect of a polymorphism in the serotonin transporter promoter on susceptibility to depression. However, we caution that it is possible that the effect has an artifactual basis, rather than a biological origin.

Internal reliability of measures of substance-related cognitive bias

AIMS There is growing interest in cognitive biases related to substance use, but evidence from the anxiety literature suggests that tasks commonly used to assess these may suffer from low internal reliability. We examined the internal reliability of the visual probe and modified Stroop tasks. DESIGN Secondary analysis of visual probe and modified Stroop task data collected across seven independent studies. SETTING Human laboratory study. PARTICIPANTS Healthy volunteers (n=408 across seven independent studies) recruited from the general population on the basis of alcohol or tobacco use. MEASUREMENTS Visual probe and modified Stroop task measures of substance-related cognitive bias. FINDINGS Measures of cognitive bias for substance-related cues, as assayed by the visual probe and the modified Stroop tasks, may not be reliable. In particular, the visual probe task showed poor internal reliability, as did unblocked versions of the modified Stroop task. CONCLUSIONS The modified Stroop task is preferable to the visual probe task as a measure of substance-related cognitive bias, on the basis of its psychometric properties. Studies using cognitive bias tasks should not assume they are reliable, and should routinely report reliability estimates where possible.

Acute alcohol impairs human goal-directed action.

There are two forms of motivated behaviour. Goal-directed action is mediated by knowledge of the consequences whereas habitual action is elicited directly by stimuli associated with the action. Alcohol may impair goal-directed control, favouring habit. To evaluate this proposal, participants were administered with 0.4 g/kg of alcohol or placebo before acquiring separate instrumental responses for chocolate and water points. Chocolate was then fed to satiety to devalue this outcome before choice between the two responses was tested in extinction. Any reduction in chocolate choice must be mediated by knowledge of the current incentive value of this outcome, i.e. must be goal-directed. Alcohol attenuated the devaluation effect on choice in extinction, but had no effect on reacquisition performance, the hedonic appraisal of rewards or acquisition of the instrumental contingencies. Acute alcohol impaired goal-directed control of action selection, favouring habit, which may mediate alcohol effects on under-controlled behaviour more broadly.

Glass Shape Influences Consumption Rate for Alcoholic Beverages

Background High levels of alcohol consumption and increases in heavy episodic drinking (binge drinking) are a growing public concern, due to their association with increased risk of personal and societal harm. Alcohol consumption has been shown to be sensitive to factors such as price and availability. The aim of this study was to explore the influence of glass shape on the rate of consumption of alcoholic and non-alcoholic beverages. Methods This was an experimental design with beverage (lager, soft drink), glass (straight, curved) and quantity (6 fl oz, 12 fl oz) as between-subjects factors. Social male and female alcohol consumers (n = 159) attended two experimental sessions, and were randomised to drink either lager or a soft drink from either a curved or straight-sided glass, and complete a computerised task identifying perceived midpoint of the two glasses (order counterbalanced). Ethical approval was granted by the Faculty of Science Research Ethics Committee at the University of Bristol. The primary outcome measures were total drinking time of an alcoholic or non-alcoholic beverage, and perceptual judgement of the half-way point of a straight and curved glass. Results Participants were 60% slower to consume an alcoholic beverage from a straight glass compared to a curved glass. This effect was only observed for a full glass and not a half-full glass, and was not observed for a non-alcoholic beverage. Participants also misjudged the half-way point of a curved glass to a greater degree than that of a straight glass, and there was a trend towards a positive association between the degree of error and total drinking time. Conclusions Glass shape appears to influence the rate of drinking of alcoholic beverages. This may represent a modifiable target for public health interventions.

Inhalation of 7.5% Carbon Dioxide Increases Threat Processing in Humans

Inhalation of 7.5% CO2 increases anxiety and autonomic arousal in humans, and elicits fear behavior in animals. However, it is not known whether CO2 challenge in humans induces dysfunction in neurocognitive processes that characterize generalized anxiety, notably selective attention to environmental threat. Healthy volunteers completed an emotional antisaccade task in which they looked toward or away from (inhibited) negative and neutral stimuli during inhalation of 7.5% CO2 and air. CO2 inhalation increased anxiety, autonomic arousal, and erroneous eye movements toward threat on antisaccade trials. Autonomic response to CO2 correlated with hypervigilance to threat (speed to initiate prosaccades) and reduced threat inhibition (increased orienting toward and slower orienting away from threat on antisaccade trials) independent of change in mood. Findings extend evidence that CO2 triggers fear behavior in animals via direct innervation of a distributed fear network that mobilizes the detection of and allocation of processing resources toward environmental threat in humans.

Effects of acute alcohol consumption on processing of perceptual cues of emotional expression

Alcohol consumption has been associated with increases in aggressive behaviour. However, experimental evidence of a direct association is equivocal, and mechanisms that may underlie this relationship are poorly understood. One mechanism by which alcohol consumption may increase aggressive behaviour is via alterations in processing of emotional facial cues. We investigated the effects of acute alcohol consumption on sensitivity to facial expressions of emotion. Participants attended three experimental sessions where they consumed an alcoholic drink (0.0, 0.2 or 0.4 g/kg), and completed a psychophysical task to distinguish expressive from neutral faces. The level of emotion in the expressive face varied across trials the threshold at which the expressive face was reliably identified and measured. We observed a significant three-way interaction involving emotion, participant sex and alcohol dose. Male participants showed significantly higher perceptual thresholds for sad facial expressions compared with female participants following consumption of the highest dose of alcohol. Our data indicate sex differences in the processing of facial cues of emotional expression following alcohol consumption. There was no evidence that alcohol altered the processing of angry facial expressions. Future studies should examine effects of alcohol expectancy and investigate the effects of alcohol on the miscategorisation of emotional expressions.

Avoidance of cigarette pack health warnings among regular cigarette smokers

BACKGROUND Previous research with adults and adolescents indicates that plain cigarette packs increase visual attention to health warnings among non-smokers and non-regular smokers, but not among regular smokers. This may be because regular smokers: (1) are familiar with the health warnings, (2) preferentially attend to branding, or (3) actively avoid health warnings. We sought to distinguish between these explanations using eye-tracking technology. METHOD A convenience sample of 30 adult dependent smokers participated in an eye-tracking study. Participants viewed branded, plain and blank packs of cigarettes with familiar and unfamiliar health warnings. The number of fixations to health warnings and branding on the different pack types were recorded. RESULTS Analysis of variance indicated that regular smokers were biased towards fixating the branding rather than the health warning on all three pack types. This bias was smaller, but still evident, for blank packs, where smokers preferentially attended the blank region over the health warnings. Time-course analysis showed that for branded and plain packs, attention was preferentially directed to the branding location for the entire 10s of the stimulus presentation, while for blank packs this occurred for the last 8s of the stimulus presentation. Familiarity with health warnings had no effect on eye gaze location. CONCLUSION Smokers actively avoid cigarette pack health warnings, and this remains the case even in the absence of salient branding information. Smokers may have learned to divert their attention away from cigarette pack health warnings. These findings have implications for cigarette packaging and health warning policy.

Effects of acute nicotine administration on ratings of attractiveness of facial cues

INTRODUCTION It has been suggested that one mechanism by which nicotine may exert an influence over behavior is by enhancing the reinforcing properties of other stimuli. We therefore sought to test the hypothesis that nicotine enhances the hedonic impact of behaviors performed in the presence of nicotine, using ratings of facial attractiveness, as we considered these to have considerable ecological validity in the context of the social environment within which cigarette smoking takes place. METHODS Male and female participants attended a single testing session and were randomized to smoke either a nicotine-containing or a denicotinized cigarette, after which they completed ratings of attractiveness of 20 male and 20 female faces. Participants were required to have abstained from smoking for 24 hr prior to testing, and the nicotine manipulation was conducted double blind. RESULTS A 2 x 2 x 2 mixed-model repeated measures analysis of variance indicated a significant main effect of cigarette, reflecting higher attractiveness ratings in the nicotinized compared with the denicotinized condition. DISCUSSION Our data indicate that nicotine increases ratings of attractiveness of facial cues. We did not observe any evidence that these effects differed between males and females. We also did not observe effects on subjective ratings of mood, suggesting that the effects we observed on ratings of attractiveness may not simply reflect global hedonic effects, or a positivity bias in questionnaire responding, in the nicotine condition.

Effects of alcohol on disinhibition towards alcohol-related cues

BACKGROUND We investigated (1) the effects of acute alcohol on inhibition of alcohol-related versus neutral cues, (2) the effects of drinking status on inhibition of alcohol-related versus neutral cues, and (3) the similarity of any effects of alcohol or drinking status across two different cue types (lexical versus pictorial). METHODS Participants received 0.0 g/kg, 0.4 g/kg or 0.6g/kg of alcohol in a between-subjects design. Healthy, heavy and light social alcohol users (n=96) completed both lexical and pictorial cue versions of an alcohol-shifting task. Participants were instructed to respond to target stimuli by pressing the spacebar, but to ignore distracter stimuli. Errors towards distracter stimuli were analysed using a series of mixed-model ANOVAs, with between-subjects factors of challenge and drinking status and within-subjects factors of distracter type (alcohol, neutral) and block (shift, non-shift). RESULTS Lexical commission error data indicated a main effect of distracter (F [1,90]=43.25, p<0.001, η(2)=0.33), which was qualified by a marginal interaction with challenge condition (F [2,90]=2.77, p=0.068, η(2)=0.06). Following an acute high dose of alcohol participants made more errors towards alcohol distracters. Pictorial commission error data indicated a significant main effect of distracter (F [1,90]=67.40, p<0.001, η(2)=0.43), such that all participants made more errors towards neutral image distracters versus alcohol distracter images. CONCLUSIONS Our results reveal acute alcohols impairment of inhibitory control may be enhanced when a response towards alcohol-related lexical stimuli is required to be withheld.

Inhalation of 7.5% carbon dioxide increases alerting and orienting attention network function

RationaleThe development of experimental models that readily translate between animals and humans is required to better integrate and clarify the biological, behavioural and cognitive mechanisms that underlie normal fear and pathological anxiety. Inhalation of low concentrations of carbon dioxide (CO2) increases anxiety and autonomic arousal in humans, triggers related behaviours in small animals, and increases selective attention to threat in healthy humans. However the effects on broader cognitive (non-emotional) processes that characterize anxiety are not known.ObjectivesTo examine the effect of 7.5 % CO2 inhalation (vs. air) on the efficiency of discrete attention networks implicated in anxiety: alerting (maintaining an alert state), orienting (the selection of information from sensory input) and executive control (resolving cognitive conflict).MethodsTwenty-three healthy human participants completed a computerized Attention Network Test (ANT) during inhalation of 7.5 % CO2 enriched and normal/medical air. Gas was administered blind to participants with inhalation order counterbalanced across participants. Measures of heart rate, blood pressure and subjective mood/anxiety were obtained at baseline and following each inhalation period.ResultsCO2 inhalation increased anxiety, autonomic arousal and the efficiency of alerting and orienting attention network function. Autonomic response to CO2 correlated with increased orienting; and CO2–induced anxiety, autonomic arousal and orienting network function increased with chronic (trait) anxiety.ConclusionsEvidence that CO2 modulates attention mechanisms involved in the temporal detection and spatial location of salient stimuli converges with evidence that CO2 triggers fear behaviour in animals via direct innervation of a distributed neural network that facilitates environmental hypervigilance.