Assessing causality in associations between cannabis use and schizophrenia risk: a two-sample Mendelian randomization study.

BACKGROUND: Observational associations between cannabis and schizophrenia are well documented, but ascertaining causation is more challenging. We used Mendelian randomization (MR), utilizing publicly available data as a method for ascertaining causation from observational data. METHOD: We performed bi-directional two-sample MR using summary-level genome-wide data from the International Cannabis Consortium (ICC) and the Psychiatric Genomics Consortium (PGC2). Single nucleotide polymorphisms (SNPs) associated with cannabis initiation (p < 10-5) and schizophrenia (p < 5 × 10-8) were combined using an inverse-variance-weighted fixed-effects approach. We also used height and education genome-wide association study data, representing negative and positive control analyses. RESULTS: There was some evidence consistent with a causal effect of cannabis initiation on risk of schizophrenia [odds ratio (OR) 1.04 per doubling odds of cannabis initiation, 95% confidence interval (CI) 1.01-1.07, p = 0.019]. There was strong evidence consistent with a causal effect of schizophrenia risk on likelihood of cannabis initiation (OR 1.10 per doubling of the odds of schizophrenia, 95% CI 1.05-1.14, p = 2.64 × 10-5). Findings were as predicted for the negative control (height: OR 1.00, 95% CI 0.99-1.01, p = 0.90) but weaker than predicted for the positive control (years in education: OR 0.99, 95% CI 0.97-1.00, p = 0.066) analyses. CONCLUSIONS: Our results provide some that cannabis initiation increases the risk of schizophrenia, although the size of the causal estimate is small. We find stronger evidence that schizophrenia risk predicts cannabis initiation, possibly as genetic instruments for schizophrenia are stronger than for cannabis initiation.

Associations of cannabis and cigarette use with psychotic experiences at age 18: findings from the Avon Longitudinal Study of Parents and Children.

BACKGROUND: A clearer understanding of the basis for the association between cannabis use and psychotic experiences (PEs) is required. Our aim was to examine the extent to which associations between cannabis and cigarette use and PEs are due to confounding. METHOD: A cohort study of 1756 adolescents with data on cannabis use, cigarette use and PEs. RESULTS: Cannabis use and cigarette use at age 16 were both associated, to a similar degree, with PEs at age 18 [odds ratio (OR) 1.48, 95% confidence interval (CI) 1.18-1.86 for cannabis and OR 1.61, 95% CI 1.31-1.98 for cigarettes]. Adjustment for cigarette smoking frequency (OR 1.27, 95% CI 0.91-1.76) or other illicit drug use (OR 1.25, 95% CI 0.91-1.73) substantially attenuated the relationship between cannabis and PEs. The attenuation was to a lesser degree when cannabis use was adjusted for in the cigarette PE association (OR 1.42, 95% CI 1.05-1.92). However, almost all of the participants used cannabis with tobacco, including those who classed themselves as non-cigarette smokers. CONCLUSIONS: Teasing out the effects of cannabis from tobacco is highly complex and may not have been dealt with adequately in studies to date, including this one. Complementary methods are required to robustly examine the independent effects of cannabis, tobacco and other illicit drugs on PEs.

Common versus psychopathology-specific risk factors for psychotic experiences and depression during adolescence.

BACKGROUND: An argument often used to support the view that psychotic experiences (PEs) in general population samples are a valid phenotype for studying the aetiology of schizophrenia is that risk factors for schizophrenia show similar patterns of association with PEs. However, PEs often co-occur with depression, and no study has explicitly tested whether risk factors for schizophrenia are shared between PEs and depression, or are psychopathology specific, while jointly modelling both outcomes. METHOD: We used data from 7030 subjects from a birth cohort study. Depression and PEs at age 18 years were assessed using self-report questionnaires and semi-structured interviews. We compared the extent to which risk factors for schizophrenia across sociodemographic, familial, neurodevelopmental, stress-adversity, emotional-behavioural and substance use domains showed different associations with PEs and depression within bivariate models that allowed for their correlation. RESULTS: Most of the exposures examined were associated, to a similar degree, with an increased risk of both outcomes. However, whereas female sex and family history of depression showed some discrimination as potential risk factors for depression and PEs, with stronger associations in the former, markers of abnormal neurodevelopment showed stronger associations with PEs. CONCLUSIONS: The argument that PEs are valid markers for studying the aetiology of schizophrenia, made simply on the basis that they share risk factors in common, is not well supported. PEs seem to be a weak index of genetic and environmental risk for schizophrenia; however, studies disentangling aetiological pathways to PEs from those impacting upon co-morbid psychopathology might provide important insights into the aetiology of psychotic disorders.

The prevalence of hazardous and harmful drinking in the UK Police Service, and their co-occurrence with job strain and mental health problems.

AIMS: Due to the stressful nature of policing, police employees are at risk of mental health problems and problematic alcohol use. We aim to determine the prevalence of hazardous and harmful alcohol use in the UK Police Service, and to explore the associations with job strain and mental health problems. METHODS: Cross-sectional data from the Airwave Health Monitoring Study (N = 40 986) included measures of alcohol consumption (total units in past week), mental health (depression, anxiety and post-traumatic stress disorder [PTSD]) and job strain. The associations between mental health and job strain with alcohol consumption (i.e. abstinence, low-risk [<14 units per week, reference group], hazardous [>14 to 35 units for women, >14 to 50 units for men], harmful [>35 units for women, >50 units for men]), were analysed using multinomial logistic regressions, adjusting for potential confounders (i.e. age, gender, ethnicity, marital status, children under 18, income and smoking status). RESULTS: A total of 32.6% of police employees reported hazardous drinking, with 3.0% drinking at harmful levels. Compared to those without a mental health problem, police employees with depression, anxiety or PTSD were twice as likely to be harmful drinkers and were also 1.3 times more likely to report abstinence. Those reporting low strain (reference group) were more likely to drink hazardously compared to those reporting high strain, which was statistically moderated by mental health. When the sample was stratified by mental health status, the association between low strain (compared to all other categories) and hazardous drinking, was significant only in those without a mental health problem. CONCLUSIONS: These findings indicate that police employees may be an occupational group at risk of alcohol harm, with one-third drinking hazardously. The J-shaped relationship between mental health and alcohol use highlights a need for an integration of mental health and alcohol services, tailored for the UK Police Service.

Effects of messaging on public support for drug consumption rooms in scotland, UK.

BACKGROUND: There is evidence to suggest that medically supervised drug consumption rooms (DCRs) may form part of responses to reduce drug-related harm. Although DCRs have been established globally, they are perceived by some to be a controversial approach in the UK, and Government has repeatedly rejected proposals to establish one in Glasgow, Scotland. As public support is an important component of policy development and enactment, we sought to investigate the effects of different types of message framing on public support for DCR. METHODS: We undertook a cross-sectional online study with a randomised design, conducted with a nationally representative sample. Participants were randomised to one of six message conditions comprising combinations of four components. All conditions included i) a basic description of a DCR, and conditions included combinations of ii) factual information; iii) pre-emptive refutation of common public concerns about DCR; and/or iv) a sympathetic narrative describing a mother whose son died from a heroin overdose. After reading each message, participants completed a bespoke measure assessing support for DCR. Data were analysed using ANCOVA. RESULTS: Complete data were obtained from 1591 participants (50.3% Female; mean age 44.9 ± 16.1 years). Compared to reading a basic description of DCR alone, there was greater support for DCR in participants receiving the refutation (p < .001); sympathetic + factual (p < .05); and sympathetic + factual + refutation (p < .001) message conditions. Presenting factual or sympathetic messages alone were not associated with increased support. CONCLUSION: Our findings suggest that public support for DCRs is not improved through communication of factual statements outlining potential benefits of the intervention alone. Advocates seeking to foster public support, and thus influence policy making, should also consider communication campaigns that address common concerns that the public might have about DCRs, and present the intervention in relation to potential benefits that they hold for people indirectly affected by drug-related harm.

Are IQ and educational outcomes in teenagers related to their cannabis use? A prospective cohort study.

There is much debate about the impact of adolescent cannabis use on intellectual and educational outcomes. We investigated associations between adolescent cannabis use and IQ and educational attainment in a sample of 2235 teenagers from the Avon Longitudinal Study of Parents and Children. By the age of 15, 24% reported having tried cannabis at least once. A series of nested linear regressions was employed, adjusted hierarchically by pre-exposure ability and potential confounds (e.g. cigarette and alcohol use, childhood mental-health symptoms and behavioural problems), to test the relationships between cumulative cannabis use and IQ at the age of 15 and educational performance at the age of 16. After full adjustment, those who had used cannabis ⩾ 50 times did not differ from never-users on either IQ or educational performance. Adjusting for group differences in cigarette smoking dramatically attenuated the associations between cannabis use and both outcomes, and further analyses demonstrated robust associations between cigarette use and educational outcomes, even with cannabis users excluded. These findings suggest that adolescent cannabis use is not associated with IQ or educational performance once adjustment is made for potential confounds, in particular adolescent cigarette use. Modest cannabis use in teenagers may have less cognitive impact than epidemiological surveys of older cohorts have previously suggested.

A two-stage cross correlation approach to template matching.

Two-stage template matching with sum of absolute differences as the similarity measure has been developed by Vanderburg and Rosenfeld [1], [2]. This correspondence shows the development of two-stage template matching with cross correlation as the similarity measure. The threshold value of the first-stage is derived analytically and its validity is verified experimentally. Considerable speed-up over the one-stage process can be obtained by introducing only a small false dismissal probability.

Precise and low-cost monitoring of plum curculio (Coleoptera: Curculionidae) pest activity in pyramid traps with cameras.

Incorporating camera systems into insect traps potentially benefits insect phenology modeling, nonlethal insect monitoring, and research into the automated identification of traps counts. Cameras originally for monitoring mammals were instead adapted to monitor the entrance to pyramid traps designed to capture the plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae). Using released curculios, two new trap designs (v.I and v.II) were field-tested alongside conventional pyramid traps at one site in autumn 2010 and at four sites in autumn 2012. The traps were evaluated on the basis of battery power, ease-of-maintenance, adaptability, required-user-skills, cost (including labor), and accuracy-of-results. The v.II design fully surpassed expectations, except that some trapped curculios were not photographed. In 2012, 13 of the 24 traps recorded every curculio entering the traps during the 18-d study period, and in traps where some curculios were not photographed, over 90% of the omissions could be explained by component failure or external interference with the motion sensor. Significantly more curculios entered the camera traps between 1800 and 0000 hours. When compared with conventional pyramid traps, the v.I traps collected a similar number of curculios. Two observed but not significant trends were that the v.I traps collected twice as many plum curculios as the v.II traps, while at the same time the v.II traps collected more than twice as many photos per plum curculio as the v.I traps. The research demonstrates that low-cost, precise monitoring of field insect populations is feasible without requiring extensive technical expertise.