Using self-report measures in neurobehavioural toxicology: Can they be trusted?

Neural correlates of metacognition impairment in opioid addiction

BACKGROUND

Individuals with substance use disorder show impaired self-awareness of ongoing behavior. This deficit suggests problems with metacognition, operationalized in the cognitive neuroscience literature as the ability to monitor and evaluate the success of one's own cognition and behavior. However, the neural mechanisms of metacognition have not been characterized in a drug-addicted population.

METHODS

Community samples of participants with opioid use disorder (OUD) (N=27) and healthy controls (N=29) performed a previously-validated fMRI metacognition task (perceptual decision-making task along with confidence ratings of performance). Measures of recent drug use and addiction severity were also acquired.

RESULTS

Individuals with OUD had lower metacognitive sensitivity than controls (i.e., disconnection between task performance and task-related confidence). Trial-by-trial analyses showed that this overall group difference was driven by (suboptimally) low confidence in OUD during correct trials. In fMRI analyses, the task engaged an expected network of brain regions (e.g., rostrolateral prefrontal cortex and dorsal anterior cingulate/supplementary motor area, both previously linked to metacognition); group differences emerged in a large ventral anterior cluster that included the medial and lateral orbitofrontal cortex and striatum (higher activation in OUD). Trial-by-trial fMRI analyses showed group differences in rostrolateral prefrontal cortex activation, which further correlated with metacognitive behavior across all participants. Exploratory analyses suggested that the behavioral and neural group differences were exacerbated by recent illicit opioid use and unexplained by general cognition.

CONCLUSIONS

With confirmation and extension of these findings, metacognition and its associated neural circuits could become new, promising therapeutic targets in addiction.

Neuropsychological symptoms in workers handling cargo from shipping containers and export logs

PURPOSE

Acute poisonings of workers handling shipping containers by fumigants and other harmful chemicals off-gassed from cargo have been reported but (sub)-chronic neuropsychological effects have not been well studied.

METHODS

This cross-sectional study assessed, using standardised questionnaires, current (past 3-months) neuropsychological symptoms in 274 container handlers, 38 retail workers, 35 fumigators, and 18 log workers, all potentially exposed to fumigants and off-gassed chemicals, and a reference group of 206 construction workers. Prevalence odds ratios (OR), adjusted for age, ethnicity, smoking, alcohol consumption, education, personality traits and BMI, were calculated to assess associations with the total number of symptoms (≥ 3, ≥ 5 or ≥ 10) and specific symptom domains (neurological, psychosomatic, mood, memory/concentration, fatigue, and sleep).

RESULTS

Compared to the reference group, exposed workers were more likely to report ≥ 10 symptoms, statistically significant only for retail workers (OR 6.8, 95% CI 1.9-24.3) who also reported more fatigue (OR 10.7, 95% CI 2.7-42.7). Container handlers with the highest exposure-duration were more likely to report ≥ 10 symptoms, both when compared with reference workers (OR 4.0, 95% CI 1.4-11.7) and with container handlers with shorter exposure duration (OR 7.5, 95% CI 1.7-32.8). The duration of container handling was particularly associated with symptoms in the memory/concentration domain, again both when compared to reference workers (OR 8.8, 95% CI 2.5-31.4) and workers with the lowest exposure-duration (OR 6.8, 95% CI 1.5-30.3).

CONCLUSION

Container handlers may have an increased risk of neuropsychological symptoms, especially in the memory/concentration domain. Retail workers may also be at risk, but this requires confirmation in a larger study.

Effective treatment and prevention of attempted suicide, anxiety, and aggressiveness with fluoxetine, despite proven use of androgenic anabolic steroids

The treatment of a man who attempted suicide after experiencing symptoms of anxiety and aggressiveness associated with the use of androgenic-anabolic steroids (AAS) is described. This report includes 30 days of inpatient treatment and a 6-month follow-up. Regular use of fluoxetine apparently prevented the onset of anxiety, depression, aggressiveness, and suicide ideation, even with the concurrent use of AAS. The urinary concentration of androgens, metabolites of AAS, and fluoxetine were monitored through analysis of urinary samples by the Brazilian Laboratory of Doping Control. Our results are congruent with previous findings describing the risk of suicide prompted by AAS use as well as the efficacy of fluoxetine in the treatment of mood disorders associated with the use of anabolic steroids.

Work ability score of solvent-exposed workers

PURPOSE

Occupational chronic solvent encephalopathy (CSE), characterized by neurocognitive dysfunction, often leads to early retirement. However, only the more severe cases are diagnosed with CSE, and little is known about the work ability of solvent-exposed workers in general. The aim was to study memory and concentration symptoms, work ability and the effect of both solvent-related and non-occupational factors on work ability, in an actively working solvent-exposed population.

METHODS

A questionnaire on exposure and health was sent to 3640 workers in four solvent-exposed fields, i.e. painters and floor-layers, boat builders, printers, and metal workers. The total number of responses was 1730. We determined the work ability score (WAS), a single question item of the Work Ability Index, and studied solvent exposure, demographic factors, Euroquest memory and concentration symptoms, chronic diseases, and employment status using univariate and multivariate analyses. The findings were compared to those of a corresponding national blue-collar reference population (n = 221), and a small cohort of workers with CSE (n = 18).

RESULTS

The proportion of workers with memory and concentration symptoms was significantly associated with solvent exposure. The WAS of solvent-exposed workers was lower than that of the national blue-collar reference group, and the difference was significant in the oldest age group (those aged over 60). Solvent-exposed worker's WAS were higher than those of workers diagnosed with CSE. The WAS were lowest among painters and floor-layers, followed by metal workers and printers, and highest among boat builders. The strongest explanatory factors for poor work ability were the number of chronic diseases, age and employment status. Solvent exposure was a weak independent risk factor for reduced WAS, comparable to a level of high alcohol consumption.

CONCLUSIONS

Even if memory and concentration symptoms were associated with higher solvent exposure, the effect of solvents on self-experienced work ability was relatively weak. This in line with the improved occupational hygiene and reduced solvent exposure levels in industrialized countries, thus the effect may be stronger in high-level exposure environments. As a single question, WAS is easily included, applicable, and recommendable in occupational screening questionnaires.

Effects of Personal Protective Equipment Use and Good Workplace Hygiene on Symptoms of Neurotoxicity in Solvent-Exposed Vehicle Spray Painters

Objectives

To assess the association between the use of personal protective equipment (PPE) and good workplace hygiene and symptoms of neurotoxicity in solvent-exposed vehicle spray painters.

Methods

Exposure control measures including PPE-use and workplace hygiene practices and symptoms of neurotoxicity were assessed in 267 vehicle repair spray painters. Symptoms were assessed using an adapted version of the EUROQUEST Questionnaire.

Results

Frequent respirator and glove use was inversely and significantly associated with symptoms of neurotoxicity in a dose-dependent manner (P < 0.05 for trend) with the strongest protective effect found for consistent glove use (odds ratios [OR] 0.1-0.2, P < 0.01, for reporting ≥10 and ≥5 symptoms). A clear dose-response trend was also observed when combining frequency of respirator and glove use (P < 0.05 for reporting ≥5 and ≥10 symptoms), with an overall reduction in risk of 90% (OR, 0.1, P < 0.01) for those who consistently used both types of PPE. Protective effects were most pronounced for the symptom domains of psychosomatic (P < 0.05 for trend, for combined PPE use), mood (P < 0.05), and memory and concentration symptoms combined (P < 0.05), with reductions in risk of >80%. Poor hygiene workplace practices, such as solvent exposure to multiple body parts (OR 3.4, P = 0.11 for reporting ≥10 symptoms), were associated with an increased risk of symptoms. When using a general workplace hygiene score derived from a combination of PPE-use and (good) workplace practice factors an inverse and significant dose-response trend was observed for reporting ≥5 (P < 0.01) and ≥10 symptoms (P < 0.01).

Conclusions

This study has shown that PPE-use and good workplace hygiene are associated with a strongly reduced risk of symptoms of neurotoxicity in solvent-exposed vehicle spray painters.

Toward biomarkers of the addicted human brain: Using neuroimaging to predict relapse and sustained abstinence in substance use disorder

The ability to predict relapse is a major goal of drug addiction research. Clinical and diagnostic measures are useful in this regard, but these measures do not fully and consistently identify who will relapse and who will remain abstinent. Neuroimaging approaches have the potential to complement these standard clinical measures to optimize relapse prediction. The goal of this review was to survey the existing drug addiction literature that either used a baseline functional or structural neuroimaging phenotype to longitudinally predict a clinical outcome, or that examined test-retest of a neuroimaging phenotype during a course of abstinence or treatment. Results broadly suggested that, relative to individuals who sustained abstinence, individuals who relapsed had (1) enhanced activation to drug-related cues and rewards, but reduced activation to non-drug-related cues and rewards, in multiple corticolimbic and corticostriatal brain regions; (2) weakened functional connectivity of these same corticolimbic and corticostriatal regions; and (3) reduced gray and white matter volume and connectivity in prefrontal regions. Thus, beyond these regions showing baseline group differences, reviewed evidence indicates that function and structure of these regions can prospectively predict - and normalization of these regions can longitudinally track - important clinical outcomes including relapse and adherence to treatment. Future clinical studies can leverage this information to develop novel treatment strategies, and to tailor scarce therapeutic resources toward individuals most susceptible to relapse.

Effects of Negative Affectivity and Odor Valence on Chemosensory and Symptom Perception and Perceived Ability to Focus on a Cognitive Task

The aim was to gain understanding for the impact of negative affectivity (NA) and odor valance on perceptual aspects during low-level odorous exposure. Fifty-five young adults who were either relatively low or high in NA (anxiety, depression, and somatization) were randomized for exposure to either limonene (pleasant odor) or pyridine (unpleasant odor). In an exposure chamber, they took part in baseline, blank and stable exposure sessions, during which they rated odor intensity, impact on ability to focus on an imagined cognitive task, and intensity of symptoms. The results showed higher ratings of negative impact on ability to focus during exposure to the unpleasant odor compared with the pleasant odor, and an association between NA and symptom intensity, with 18% of the variance in symptom intensity explained by somatization. The association between NA and symptom intensity was found to be driven by the factor sex. These results imply (a) that prior findings of odorous exposure that interfere negatively with work performance may be due to impact of an unpleasant odor on ability to focus on cognitive tasks and (b) that there are associations between NA, sex, and symptoms that may partly be referred to attentiveness to and interpretation of bodily sensations.

Incubation of Cue-Induced Craving in Adults Addicted to Cocaine Measured by Electroencephalography

IMPORTANCE

A common trigger for relapse in drug addiction is the experience of craving via exposure to cues previously associated with drug use. Preclinical studies have consistently demonstrated incubation of cue-induced drug-seeking during the initial phase of abstinence, followed by a decline over time. In humans, the incubation effect has been shown for alcohol, nicotine, and methamphetamine addictions, but not for heroin or cocaine addiction. Understanding the trajectory of cue-induced craving during abstinence in humans is of importance for addiction medicine.

OBJECTIVE

To assess cue-induced craving for cocaine in humans using both subjective and objective indices of cue-elicited responses.

DESIGN, SETTING, AND PARTICIPANTS

Seventy-six individuals addicted to cocaine with varying durations of abstinence (ie, 2 days, 1 week, 1 month, 6 months, and 1 year) participated in this laboratory-based cross-sectional study from June 19, 2007, to November 26, 2012. The late positive potential component of electroencephalography, a recognized marker of incentive salience, was used to track motivated attention to drug cues across these self-selected groups. Participants also completed subjective ratings of craving for cocaine before presentation of a cue, and ratings of cocaine "liking" (hedonic feelings toward cocaine) and "wanting" (craving for cocaine) after presentation of cocaine-related pictures. Data analysis was conducted from June 5, 2015, to March 30, 2016.

MAIN OUTCOMES AND MEASURES

The late positive potential amplitudes and ratings of liking and wanting cocaine in response to cocaine-related pictures were quantified and compared across groups.

RESULTS

Among the 76 individuals addicted to cocaine, 19 (25%) were abstinent for 2 days, 20 (26%) were abstinent for 1 week, 15 (20%) were abstinent for 1 month, 12 (16%) were abstinent for 6 months, and 10 (13%) were abstinent for 1 year. In response to drug cues, the mean (SD) late positive potential amplitudes showed a parabolic trajectory that was higher at 1 (1.26 [1.36] µV) and 6 (1.17 [1.19] µV) months of abstinence and lower at 2 days (0.17 [1.09] µV), 1 week (0.36 [1.26] µV), and 1 year (-0.27 [1.74] µV) of abstinence (P = .02, partial η2 = 0.16). In contrast, the subjective assessment of baseline craving (mean [SD] rating: 2 days, 26.05 [9.85]; 1 week, 18.70 [11.01]; 1 month, 10.87 [10.70]; 6 months, 6.92 [8.47]; and 1 year, 3.00 [3.77]) and cue-induced liking (mean [SD] rating: 2 days, 3.06 [2.34]; 1 week, 2.33 [2.87]; 1 month, 1.15 [2.03]; 6 months, 1.00 [2.24]; and 1 year, 1.00 [1.26]) and wanting (mean [SD] rating: 2 days, 3.44 [2.62]; 1 week, 2.72 [2.87]; 1 month, 1.46 [2.33]; 6 months, 1.00 [2.16]; and 1 year, 1.00 [1.55]) of cocaine showed a linear decline from 2 days to 1 year of abstinence (P ≤ .001, partial η2 > 0.26).

CONCLUSIONS AND RELEVANCE

The late positive potential responses to drug cues, indicative of motivated attention, showed a trajectory similar to that reported in animal models. In contrast, we did not detect incubation of subjective cue-induced craving. Thus, the objective electroencephalographic measure may possibly be a better indicator of vulnerability to cue-induced relapse than subjective reports of craving, although this hypothesis must be empirically tested. These results suggest the importance of deploying intervention between 1 month and 6 months of abstinence, when addicted individuals may be most vulnerable to, and perhaps least cognizant of, risk of relapse.

Solvent neurotoxicity in vehicle collision repair workers in New Zealand

OBJECTIVES

To assess whether solvent use and workplace practices in the vehicle collision repair industry are associated with symptoms of neurotoxicity in spray painters and panel beaters (auto body repair workers).

METHODS

Neurobehavioural symptoms were assessed using a cross-sectional study design in 370 vehicle collision repair and 211 reference workers using the EUROQUEST questionnaire. Full-shift airborne solvent levels were measured in a subset (n=92) of collision repair workers.

RESULTS

Solvent exposures were higher in spray painters than in panel beaters, but levels were below current international exposure standards. Collision repair workers were more likely to report symptoms of neurotoxicity than reference workers with ORs of 2.0, 2.4 and 6.4 (all p<0.05) for reporting ≥5, ≥10 and ≥15 symptoms respectively. This trend was generally strongest for panel beaters (ORs of 2.1, 3.3 and 8.2 for ≥5, ≥10 and ≥15 symptoms respectively). Associations with specific symptom domains showed increased risks for neurological (OR 4.2), psychosomatic (OR 3.2), mood (OR 2.1), memory (OR 2.9) and memory and concentration symptoms combined (OR 2.4; all p<0.05). Workers who had worked for 10-19 years or 20+ years in the collision repair industry reported consistently more symptoms than those who had only worked less than 10 years even after adjusting for age. However, those who worked more than 20 years generally reported fewer symptoms than those who worked 10-19 years, suggesting a possible healthy worker survivor bias.

CONCLUSIONS

Despite low airborne solvent exposures, vehicle collision repair spray painters and panel beaters continue to be at risk of symptoms of neurotoxicity.

Low brain oxygenation and differences in neuropsychological outcomes following severe pediatric TBI

PURPOSE

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in children. Preventing secondary injury by controlling physiological parameters (e.g. intracranial pressure [ICP], cerebral perfusion pressure [CPP] and brain tissue oxygen [PbtO2]) has a potential to improve outcome. Low PbtO2 is independently associated with poor clinical outcomes in both adults and children. However, no studies have investigated associations between low PbtO2 and neuropsychological and behavioural outcomes following severe pediatric TBI (pTBI).

METHODS

We used a quasi-experimental case-control design to investigate these relationships. A sample of 11 TBI patients with a Glasgow Coma Scale score ≤8 who had PbtO2 and ICP monitoring at the Red Cross War Memorial Children's Hospital underwent neuropsychological evaluation ≥1 year post-injury. Their performance was compared to that of 11 demographically matched healthy controls. We then assigned each TBI participant into one of two subgroups, (1) children who had experienced at least one episode of PbtO2 ≤ 10 mmHg or (2) children for whom PbtO2 > 10 mmHg throughout the monitoring period, and compared their results on neuropsychological evaluation.

RESULTS

TBI participants performed significantly more poorly than controls in several cognitive domains (IQ, attention, visual memory, executive functions and expressive language) and behavioural (e.g. externalizing behaviour) domains. The PbtO2 ≤ 10 mmHg group performed significantly worse than the PbtO2 > 10 mmHg group in several cognitive domains (IQ, attention, verbal memory, executive functions and expressive language), but not on behavioural measures.

CONCLUSION

Results demonstrate that low PbtO2 may be prognostic of not only mortality but also neuropsychological outcomes.

[Study of self-reported health of people living near point sources of environmental pollution: a review. Second part: analysis of results and perspectives]

BACKGROUND

Epidemiological studies have investigated the health impacts of local sources of environmental pollution using as an outcome variable self-reported health, reflecting the overall perception interviewed people have of their own health. This work aims at analyzing the advantages and the results of this approach. This second part presents the results of the studies.

METHODS

Based on a literature review (51 papers), this article presents an analysis of the contribution of self-reported health to epidemiological studies investigating local sources of environmental pollution. It discusses the associations between self-reported health and exposure variables, and other risk factors that can influence health reporting.

RESULTS

Studies using self-reported health showed that local sources can be associated with a wide range of health outcomes, including an impact on mental health and well-being. The perception of pollution, especially sensory information such as odors, affects self-reported health. Attitudes referring to beliefs, worries and personal behaviors concerning the source of pollution have a striking influence on reported health. Attitudes can be used to estimate the reporting bias in a biomedical approach, and also constitute the main explanatory factors in biopsychosocial studies taking into account not only the biological, physical, and chemical factors but also the psychological and social factors at stake in a situation of environmental exposure.

CONCLUSION

Studying self-reported health enables a multifactorial approach to health in a context of environmental exposure. This approach is most relevant when conducted within a multidisciplinary framework involving human and social sciences to better understand psychosocial factors. The relevance of this type of approach used as an epidemiological surveillance tool to monitor local situations should be assessed with regard to needs for public health management of these situations.

[Study of self-reported health of people living near point sources of environmental pollution: a review. First part: health indicators]

BACKGROUND

Epidemiological studies have investigated the health impacts of local sources of environmental pollution using as an outcome variable self-reported health, reflecting the overall perception interviewed people have of their own health. This work aims at analyzing the advantages and the results of this approach. A first step focused on describing the indicators.

METHODS

The literature on indicators of self-reported health was reviewed, leading to a discussion on data collection, selection of health effects, data processing, and construction of indicators.

RESULTS

The literature review concerned 51 articles. The use of self-reported health indicators allowed the studies to take into account the health concerns and complaints of populations exposed to environmental pollution. Various indicators of self-reported health were used in the studies. They measured physical, psychological and general dimensions of health. Standardized questionnaires were used less often than ad hoc questionnaires (78% of studies) developed to fit the needs of a given study. Three standardized questionnaires were used more frequently: the MOS Short-Form Health Survey (SF-36) to measure general health perceptions, the General Health Questionnaire (GHQ), and the Symptoms Checklist (SCL-90) to measure psychological distress.

CONCLUSION

The choice of self-reported health indicators is a compromise between specificity of the studied health issues within a given environment and standardization of the questionnaires used to measure them. Such standardization is necessary to ensure the validity and the reliability of the information collected across time and situations. The psychometric properties of the measuring questionnaires are rarely estimated or verified when they are used.

The effects of demand characteristics on research participant behaviours in non-laboratory settings: a systematic review

Background

The concept of demand characteristics, which involves research participants being aware of what the researcher is investigating, is well known and widely used within psychology, particularly in laboratory-based studies. Studies of this phenomenon may make a useful contribution to broader consideration of the effects of taking part in research on participant behaviour. This systematic review seeks to summarise data from studies of the effects of demand characteristics on participant behaviours in non-laboratory settings.

Methodology/Principal Findings

Electronic databases were searched to identify eligible studies. These had to be purposely designed to evaluate possible effects of demand characteristics on at least one behavioural outcome under the autonomous control of the participants and use longitudinal study designs. Only 7 studies were included, 6 providing observational data and 1 experimental study, with 5 studies involving examination of possible effects on health behaviours. Although studies provided some evidence of effects of demand characteristics on participant behaviour, heterogeneous operationalisation of the construct, the limited number of studies and poor quality of study designs made synthesis and interpretation of study findings challenging.

Conclusions/Significance

Although widely accepted as important in psychology, there have been few dedicated studies of the effects of demand characteristics on research participant behaviours outside laboratory settings. This body of literature does not currently contribute to the wider study of research participation effects. A systematic review of data from laboratory-based studies is needed, as are high-quality primary studies in non-laboratory settings. We suggest that unqualified use of the term demand characteristics should be abandoned.

High perceived stress is linked to afternoon cortisol levels and greater symptom distress in patients with localized prostate cancer

BACKGROUND

Patients treated with radical prostatectomy (RP) or radiation therapy (RT) for prostate cancer can experience stress and symptoms that impact quality of life.

OBJECTIVE

The objectives of this study were to describe cortisol levels, perceived stress, symptoms, and symptom distress; compare differences in variables measured between RP and RT; and identify associations among cortisol levels, perceived stress, symptoms, and symptom distress in patients treated for localized prostate cancer.

METHODS

A descriptive, cross-sectional study was conducted with 53 patients (RP n = 24, RT n = 29). Data from saliva, questionnaires, and interviews were collected within 3 months of treatment. Saliva samples were collected at 4 times over 2 consecutive days. Data were analyzed using descriptive statistics, correlations, and regressions.

RESULTS

A robust diurnal rhythm of cortisol secretion with heightened levels in the early morning and lowered levels late in the day was found. On average, the entire sample had moderate symptoms and symptom distress for urinary, bowel, and sexual dysfunction. The RP group reported significantly more urinary and sexual dysfunction symptoms and fewer bowel symptoms than did the RT group. Perceived stress was positively correlated with higher afternoon cortisol levels and greater symptom distress.

CONCLUSION

Moderate symptoms and symptom distress found in our sample indicate the need for interventions to address these outcomes in men treated for prostate cancer. Self-reported perceived stress can be used to assess the stress level and symptom distress in clinic setting.

IMPLICATIONS FOR PRACTICE

Patients treated for prostate cancer with RP or RT should be assessed for symptoms and symptom distress and targeted for early symptom management interventions.

Preliminary evidence for white matter metabolite differences in marijuana-dependent young men using 2D J-resolved magnetic resonance spectroscopic imaging at 4 Tesla

Chronic marijuana (MRJ) use is associated with altered cognition and mood state, altered brain metabolites, and functional and structural brain changes. The objective of this study was to apply proton magnetic resonance spectroscopic imaging (MRSI) to compare proton metabolite levels in 15 young men with MRJ dependence and 11 healthy non-using (NU) young men. Spectra were acquired at 4.0 Tesla using 2D J-resolved MRSI to resolve coupled resonances in J-space and to quantify the entire J-coupled spectral surface of metabolites from voxels containing basal ganglia and thalamus, temporal and parietal lobes, and occipital white and gray matter. This method permitted investigation of high-quality spectra for regression analyses to examine metabolites relative to tissue type. Distribution of myo-inositol (mI)/creatine (Cr) was altered in the MRJ group whereas the NU group exhibited higher mI/Cr in WM than GM, this pattern was not observed in MRJ subjects. Significant relationships observed between global mI/Cr and distribution in WM, and self-reported impulsivity and mood symptoms were also unique between MRJ and NU groups. These preliminary findings suggest that mI, and distribution of this glial metabolite in WM, is altered by MRJ use and is associated with behavioral and affective features reported by young MRJ-dependent men.

The effects of psychopathology on subjective experience of side effects of antipsychotics in patients with schizophrenia

This study was conducted to delineate the relationship between self-reported side effects and psychopathology in schizophrenia patients. Patients with schizophrenia completed the Liverpool University Neuroleptic Side Effects Rating Scale for subjective side effects and were evaluated with the Positive and Negative Syndrome Scale for their psychopathology. Based on a series of multiple linear regression analyses, we derived a model accounting for the relationships among the specific domains of psychopathology and red herring (RH) items of the Liverpool University Neuroleptic Side Effects Rating Scale in predicting subjective side effects. The model with anxiety/depressive symptoms and RH serving as mediators between positive symptoms and side effects was found to show good fit. Positive symptoms caused mostly anxiety symptoms and tendency to report RH items, whereby resulting in over-generalized reporting of subjective side effects. However, a large proportion of variance of side effects was explained by RH, which was only partially explained by positive symptoms alone. Therefore, patients with severe levels of positive and anxiety/depressive symptoms may be prone to nocebo-like effects of antipsychotics. Studies that include acute stage patients presenting severe levels of these symptoms should not rely only on the subjective report of side effects but also apply objective measures.

Theories of addiction: methamphetamine users' explanations for continuing drug use and relapse

A variety of preclinical models have been constructed to emphasize unique aspects of addiction-like behavior. These include Negative Reinforcement ("Pain Avoidance"), Positive Reinforcement ("Pleasure Seeking"), Incentive Salience ("Craving"), Stimulus Response Learning ("Habits"), and Inhibitory Control Dysfunction ("Impulsivity"). We used a survey to better understand why methamphetamine-dependent research volunteers (N = 73) continue to use methamphetamine, or relapse to methamphetamine use after a period of cessation of use. All participants met DSM-IV criteria for methamphetamine abuse or dependence, and did not meet criteria for other current Axis I psychiatric disorders or dependence on other drugs of abuse, other than nicotine. The questionnaire consisted of a series of face-valid questions regarding drug use, which in this case referred to methamphetamine use. Examples of questions include: "Do you use drugs mostly to make bad feelings like boredom, loneliness, or apathy go away?", "Do you use drugs mostly because you want to get high?", "Do you use drugs mostly because of cravings?", "Do you find yourself getting ready to take drugs without thinking about it?", and "Do you impulsively take drugs?". The scale was anchored at 1 (not at all) and 7 (very much). For each question, the numbers of participants rating each question negatively (1 or 2), neither negatively or affirmatively (3-5), and affirmatively (6 or 7) were tabulated. The greatest number of respondents (56%) affirmed that they used drugs due to "pleasure seeking." The next highest categories selected were "impulsivity" (27%) and "habits"(25%). Surprisingly, many participants reported that "pain avoidance" (30%) and "craving" (30%) were not important for their drug use. Results from this study support the contention that methamphetamine users (and probably other drug users as well) are more heterogeneous than is often appreciated, and imply that treatment development might be more successful if treatments targeted subtypes of patients, though a range of limitations to the approach used are acknowledged.

Symptoms of chronic solvent encephalopathy: Euroquest questionnaire study

The aim was to study the symptomatology of chronic solvent encephalopathy (CSE), and the persistence of the symptoms. We examined how Euroquest, a neurotoxic symptom questionnaire, distinguished workers with verified CSE from unexposed employees, and evaluated symptom cut-off for CSE. Another aim was to study the effect of age on the responses. CSE cases confirmed at the Finnish Institute of Occupational Health had completed Euroquest either before their first investigation procedure (CSE-1 group, n=33), or before attending a routine control for previously diagnosed CSE (CSE-2, n=43). Non-exposed carpenters served as referents (n=292). We studied responses to single questions and to symptom domains. The domain with the highest AUC (area under the ROC: Receiver Operating Characteristic Curve) value was chosen to study cut-off points. CSE groups reported nearly all 59 symptoms more frequently than the carpenters. There was only little difference between younger and older carpenters. CSE-1 reported 12 symptoms more often than CSE-2, but no significant differences were found in the memory and concentration domain, which had the highest AUC, above 0.9. Using a three out of 10 symptoms cut-off point, 97% of the CSE-1 cases and 80% of the carpenters were classified correctly. At a four-symptom cut-off, the sensitivity was 93% and specificity 87%. The memory and concentration as core symptoms distinguished CSE cases from unexposed workers and remain, even after cessation of exposure. The effect of age on Euroquest was minor. Euroquest is recommended for the screening of CSE in solvent-exposed work-force and in the diagnostic process of CSE. We propose three memory and concentration symptoms as cut-off to minimize under-detection.

Symptom screening in detection of occupational solvent-related encephalopathy

OBJECTIVES

Sensitive and easily applicable methods are needed for early detection of central nervous system adverse effects related to occupational solvent exposure. The present study evaluates how symptom screening works in practice.

METHODS

A cross-sectional questionnaire survey was conducted on 2,000 construction workers, including painters and carpenters, in Finland. Scores were calculated for symptoms relevant for chronic solvent encephalopathy (CSE). Responses on exposure and health were compared between subjects with high score (N = 28) and all other respondents. The respondents with the highest scores, regardless of their occupation and exposure, were invited for clinical examination to investigate the aetiologies of the symptoms. If the examination resulted in a suspicion of CSE, a multidisciplinary differential diagnostic follow-up procedure was performed.

RESULTS

The respondents with highest symptom scores were more exposed to solvents than those with lower scores (P < 0.001) and reported more often physician-diagnosed diseases, especially psychiatric disorders (P < 0.001). They also consumed more alcohol (P = 0.005) and were more often unemployed or unable to work (P < 0.001). In the clinical examination, sleep disturbances, somatic disorders, depression, unemployment, and alcohol use were commonly found in addition to considerable solvent exposure history and clinical neurological findings. Further examinations and a diagnostic follow-up verified three cases of encephalopathy. One case was a CSE, an occupational disease. The other two encephalopathy cases had multifactorial aetiology including solvents.

CONCLUSIONS

Screening in active workforce for symptoms of cognitive dysfunction identifies highly solvent-exposed workers and also reveals occupational and non-occupational cases of encephalopathy. Evaluation of differential diagnostic conditions is essential in the detection of CSE. A stepwise model is proposed.

Manganese cumulative exposure and symptoms: a follow-up study of alloy workers

Long-term exposure to manganese (Mn) particulates through inhalation can be neurotoxic, with deficits in neuromotor and cognitive domains. Mn-exposed individuals also report symptoms, including fatigue, mood changes, irritability, concentration difficulties, and sweating in the absence of physical effort. The long-term course of Mn-related symptoms after cessation of exposure has never been examined. Male workers from a Mn-alloy production plant participated in a study on nervous system functions (initial examination), and were followed-up 14 years after plant closure. The relation between self-reported symptoms and Mn cumulative exposure index (CEI) was examined among 71 Mn-alloy workers and 71 referents. Symptoms from the questionnaire were grouped into categories, and the reported frequency was compared between referents and Mn-alloy workers in each Mn CEI tertile using General Linear Models, controlling for age, education, and alcohol consumption. A gradual increase in symptoms frequency was observed for complaints related to hearing and movement control both at initial and follow-up examination, and fatigue and autonomic nervous system only at initial examination. In addition, an exposure-effect relation was apparent for symptoms related to memory, concentration and balance reported at both examinations, with Mn-workers in the highest CEI tertile reporting the highest level of symptomatology. Sleeping complaints were not associated with exposure to Mn, while musculoskeletal pain and muscular weakness were reported more often by Mn-workers than referents but were not clearly related to CEI. The findings suggest that former Mn-alloy workers continue to perceive symptoms many years after cessation of exposure. Despite the limitations of self-reported symptoms, subjective complaints are an important part of a health assessment since they relate directly to perceived health status and day-to-day functioning.