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Acute cannabis administration can produce transient psychotic-like effects in healthy individuals. However, the mechanisms through which this occurs and which factors predict vulnerability remain unclear. We investigate whether cannabis inhalation leads to psychotic-like symptoms and speech illusion; and whether cannabidiol (CBD) blunts such effects (study 1) and adolescence heightens such effects (study 2).
Two double-blind placebo-controlled studies, assessing speech illusion in a white noise task, and psychotic-like symptoms on the Psychotomimetic States Inventory (PSI). Study 1 compared effects of Cann-CBD (cannabis containing Δ-9-tetrahydrocannabinol (THC) and negligible levels of CBD) with Cann+CBD (cannabis containing THC and CBD) in 17 adults. Study 2 compared effects of Cann-CBD in 20 adolescents and 20 adults. All participants were healthy individuals who currently used cannabis.
In study 1, relative to placebo, both Cann-CBD and Cann+CBD increased PSI scores but not speech illusion. No differences between Cann-CBD and Cann+CBD emerged. In study 2, relative to placebo, Cann-CBD increased PSI scores and incidence of speech illusion, with the odds of experiencing speech illusion 3.1 (95% CIs 1.3–7.2) times higher after Cann-CBD. No age group differences were found for speech illusion, but adults showed heightened effects on the PSI.
Inhalation of cannabis reliably increases psychotic-like symptoms in healthy cannabis users and may increase the incidence of speech illusion. CBD did not influence psychotic-like effects of cannabis. Adolescents may be less vulnerable to acute psychotic-like effects of cannabis than adults.
Sexual dysfunction occurs in 40%-60% of patients with major depressive disorder (MDD), due to either the illness itself and/or the effects of antidepressant treatment. The phase-2 CLARITY trial recently demonstrated the efficacy of adjunctive pimavanserin (PIM) for MDD when added to ongoing selective serotonin or serotonin–norepinephrine reuptake inhibitor (SSRI/SNRI) treatment. No new safety observations were reported in this study. This post-hoc analysis examines the potential impact of PIM treatment on sexual function.
Study methodology has been presented previously (APA 2019). Adult male and female patients with moderate-to-severe MDD were randomized to PIM 34 mg/day (n=51) or placebo (PBO, n=152) added to ongoing SSRI/SNRI treatment. Massachusetts General Hospital–Sexual Functioning Inventory (MGH-SFI) and Hamilton Depression Rating Scale, 17-item version (HAMD-17) item 14 (sexual interest) scores were examined by analysis of covariance.
Adjunctive PIM resulted in significantly greater 5-week reduction (improvement) relative to SSRI/SNRI treatment plus placebo on mean MGH-SFI scores (difference –0.634, SE 0.167; P<0.001; effect size [ES], Cohen’s d 0.614). Similarly, PIM resulted in greater improvement compared with placebo on individual MGH-SFI items that applied to both males and females: Interest in Sex (P=0.006; ES=0.483), Ability to Get Sexually Aroused/Excited (P=0.001; ES=0.560), Ability to Achieve Orgasm (P<0.001; ES=0.609), Overall Sexual Satisfaction (P=0.003; ES=0.524). HAMD-17 item 14 scores were also significantly more reduced (improved) with PIM (P<0.001; ES=0.574).
These results underscore the potential of adjunctive PIM for improving sexual function in patients with MDD and inadequate response to SSRIs/SNRIs. Potential benefits should be confirmed in further studies.
Depression is the leading cause of disability worldwide, with fewer than 50% of treated patients achieving full remission. This study (“CLARITY,” ACP-103-042: NCT03018340) examined the 5-HT2A inverse agonist pimavanserin (PIM) as a potential adjunctive treatment for major depressive disorder (MDD).
Adult female and male subjects with a DSM-5 primary diagnosis of a major depressive episode as part of MDD, inadequate response to ongoing SSRIs or SNRIs of adequate dose and duration as confirmed by the Massachusetts General Hospital Antidepressant Treatment History Questionnaire, and a MADRS total score >20 were randomized to PIM 34 mg/day or placebo (PBO) added to their SSRI/SNRI treatment. A sequential parallel comparison design was used, consisting of two 5-week stages. PBO nonresponders in Stage-1 who met prespecified criteria were re-randomized to PIM or PBO for the second period (Stage-2). The primary efficacy measure was the weighted average of Stage-1 and Stage-2 total scores of the HAMD-17.
Of the 207 patients enrolled, 52 received PIM, and 155 received PBO in Stage 1. Mean age was 46.2 years, and 72.9% of patients were female. Baseline MADRS total (mean [SD]: 31.5 [0.4]) and HAMD-17 total scores (22.2 [0.3]) indicated a moderate overall severity of illness. PIM met the primary endpoint, reducing the weighted Stage-1/Stage-2 HAMD-17 total score relative to PBO (least-square means [LSM] difference, –1.7; standard error [SE], 0.9; P=0.04). Stage-1 PIM patients demonstrated highly significant 5-week improvement on the HAMD-17 (LSM difference=–4.0, SE=1.1; P<0.001; effect size, Cohen’s d: 0.626), separating from placebo by the end of Week 1 (LSM difference=–1.7, SE=0.8; P=0.04). Stage-2 results showed no significant separation among Stage-1 placebo nonresponders (P=0.69). In Stage 2, a substantively smaller number of subjects (n=58) were rerandomized than planned, likely due to restrictive criteria for re-randomization. Greater overall improvement was seen with PIM relative to PBO on the key secondary endpoint, the Sheehan Disability Scale (LSM difference=–0.8, SE=0.3; P=0.004), and positive results were also seen on 7 of the 11 other secondary endpoints, including responder rate (≥50% reduction in HAMD-17 total; P=0.007), Massachusetts General Hospital Sexual Functioning Index (P<0.001), and Karolinska Sleepiness Scale for daytime sleepiness (P=0.02). Discontinuations due to adverse events were low (PIM 1.2%, PBO 3.2%). One serious adverse event was reported in each treatment group, deemed unrelated to treatment. No deaths were reported. Laboratory assessments, electrocardiography, and changes in vital signs were unremarkable, and no new safety signals were reported.
Study data provide evidence of the efficacy, safety, and tolerability of adjunctive PIM in treating MDD inadequately responsive to SSRI or SNRI therapy. Efforts to confirm these results are ongoing in a Phase 3 program.
Daily use of high-potency cannabis has been reported to carry a high risk for developing a psychotic disorder. However, the evidence is mixed on whether any pattern of cannabis use is associated with a particular symptomatology in first-episode psychosis (FEP) patients.
We analysed data from 901 FEP patients and 1235 controls recruited across six countries, as part of the European Network of National Schizophrenia Networks Studying Gene-Environment Interactions (EU-GEI) study. We used item response modelling to estimate two bifactor models, which included general and specific dimensions of psychotic symptoms in patients and psychotic experiences in controls. The associations between these dimensions and cannabis use were evaluated using linear mixed-effects models analyses.
In patients, there was a linear relationship between the positive symptom dimension and the extent of lifetime exposure to cannabis, with daily users of high-potency cannabis having the highest score (B = 0.35; 95% CI 0.14–0.56). Moreover, negative symptoms were more common among patients who never used cannabis compared with those with any pattern of use (B = −0.22; 95% CI −0.37 to −0.07). In controls, psychotic experiences were associated with current use of cannabis but not with the extent of lifetime use. Neither patients nor controls presented differences in depressive dimension related to cannabis use.
Our findings provide the first large-scale evidence that FEP patients with a history of daily use of high-potency cannabis present with more positive and less negative symptoms, compared with those who never used cannabis or used low-potency types.
The Green et al., Paranoid Thoughts Scale (GPTS) – comprising two 16-item scales assessing ideas of reference (Part A) and ideas of persecution (Part B) – was developed over a decade ago. Our aim was to conduct the first large-scale psychometric evaluation.
In total, 10 551 individuals provided GPTS data. Four hundred and twenty-two patients with psychosis and 805 non-clinical individuals completed GPTS Parts A and B. An additional 1743 patients with psychosis and 7581 non-clinical individuals completed GPTS Part B. Factor analysis, item response theory, and receiver operating characteristic analyses were conducted.
The original two-factor structure of the GPTS had an inadequate model fit: Part A did not form a unidimensional scale and multiple items were locally dependant. A Revised-GPTS (R-GPTS) was formed, comprising eight-item ideas of reference and 10-item ideas of persecution subscales, which had an excellent model fit. All items in the new Reference (a = 2.09–3.67) and Persecution (a = 2.37–4.38) scales were strongly discriminative of shifts in paranoia and had high reliability across the spectrum of severity (a > 0.90). The R-GPTS score ranges are: average (Reference: 0–9; Persecution: 0–4); elevated (Reference: 10–15; Persecution: 5–10); moderately severe (Reference: 16–20; Persecution:11–17); severe (Reference: 21–24; Persecution: 18–27); and very severe (Reference: 25+; Persecution: 28+). Recommended cut-offs on the persecution scale are 11 to discriminate clinical levels of persecutory ideation and 18 for a likely persecutory delusion.
The psychometric evaluation indicated a need to improve the GPTS. The R-GPTS is a more precise measure, has excellent psychometric properties, and is recommended for future studies of paranoia.
There are high rates of obesity and low self-esteem in patients with psychosis. The occurrence of negative voice content directly about appearance is therefore plausible. Derogatory comments about appearance are likely to be distressing, increase depression and contribute to social withdrawal.
To systematically assess the occurrence of voice content regarding appearance and identify correlates.
Sixty patients experiencing verbal auditory hallucinations at least once a week in the context of non-affective psychosis completed a measure assessing positive and negative voice content about appearance. They also completed assessments about body image, self-esteem, psychiatric symptoms and well-being.
Fifty-five (91.7%) participants reported hearing voices comment on their appearance. A total of 54 (90%) patients reported negative voice content about their appearance with 30 (50%) patients experienced negative appearance comments on a daily basis. The most common negative comment was ‘the voices tell me that I am ugly’ (n = 48, 80%). There were 39 (65%) patients who reported positive voice content on appearance. The most frequent positive comment was ‘I look as nice as other people’ (n = 26, 43.3%). Negative voice content about appearance was associated with body image concerns, paranoia, voice hearing severity, depression, worry, negative self-beliefs and safety-seeking behaviours. Positive appearance voice content was associated with greater body esteem and well-being and lower levels of depression and insomnia.
Voice content about appearance is very common for patients seen in clinical services. Negative voice content may reflect – and subsequently reinforce – negative beliefs about one's appearance, low self-esteem, worry and paranoia.
The period before the formation of a persecutory delusion may provide causal insights. Patient accounts are invaluable in informing this understanding.
To inform the understanding of delusion formation, we asked patients about the occurrence of potential causal factors – identified from a cognitive model – before delusion onset.
A total of 100 patients with persecutory delusions completed a checklist about their subjective experiences in the weeks before belief onset. The checklist included items concerning worry, images, low self-esteem, poor sleep, mood dysregulation, dissociation, manic-type symptoms, aberrant salience, hallucinations, substance use and stressors. Time to reach certainty in the delusion was also assessed.
Most commonly it took patients several months to reach delusion certainty (n = 30), although other patients took a few weeks (n = 24), years (n = 21), knew instantly (n = 17) or took a few days (n = 6). The most frequent experiences occurring before delusion onset were: low self-confidence (n = 84); excessive worry (n = 80); not feeling like normal self (n = 77); difficulties concentrating (n = 77); going over problems again and again (n = 75); being very negative about the self (n = 75); images of bad things happening (n = 75); and sleep problems (n = 75). The average number of experiences occurring was high (mean 23.5, s.d. = 8.7). The experiences clustered into six main types, with patients reporting an average of 5.4 (s.d. = 1.0) different types.
Patients report numerous different experiences in the period before full persecutory delusion onset that could be contributory causal factors, consistent with a complex multifactorial view of delusion occurrence. This study, however, relied on retrospective self-report and could not determine causality.
The National Institute for Health and Care Excellence referral guidelines prompting urgent two-week referrals were updated in 2015. Additional symptoms with a lower threshold of 3 per cent positive predictive values were integrated. This study aimed to examine whether current pan-London urgent referral guidelines for suspected head and neck cancer lead to efficient and accurate referrals by assessing frequency of presenting symptoms and risk factors, and examining their correlation with positive cancer diagnoses.
The risk factors and symptoms of 984 consecutive patients (over a six-month period in 2016) were collected retrospectively from urgent referral letters to University College London Hospital for suspected head and neck cancer.
Only 37 referrals (3.76 per cent) resulted in a head and neck cancer diagnosis. Four of the 23 recommended symptoms demonstrated statistically significant results. Nine of the 23 symptoms had a positive predictive value of over 3 per cent.
The findings indicate that the current referral guidelines are not effective at detecting patients with cancer. Detection rates have decreased from 10–15 per cent to 3.76 per cent. A review of the current head and neck cancer referral guidelines is recommended, along with further data collection for comparison.
The diurnal feeding patterns of dairy cows affects the 24 h robot utilisation of pasture-based automatic milking systems (AMS). A decline in robot utilisation between 2400 and 0600 h currently occurs in pasture-based AMS, as cow feeding activity is greatly reduced during this time. Here, we investigate the effect of a temporal variation in feed quality and quantity on cow feeding behaviour between 2400 and 0600 h as a potential tool to increase voluntary cow trafficking in an AMS at night. The day was allocated into four equal feeding periods (0600 to 1200, 1200 to 1800, 1800 to 2400 and 2400 to 0600 h). Lucerne hay cubes (CP = 19.1%, water soluble carbohydrate = 3.8%) and oat, ryegrass and clover hay cubes with 20% molasses (CP = 11.8%, water soluble carbohydrate = 10.7%) were offered as the ‘standard’ and ‘preferred’ (preference determined previously) feed types, respectively. The four treatments were (1) standard feed offered ad libitum (AL) throughout 24 h; (2) as per AL, with preferred feed replacing standard feed between 2400 and 0600 h (AL + P); (3) standard feed offered at a restricted rate, with quantity varying between each feeding period (20:10:30:60%, respectively) as a proportion of the (previously) measured daily ad libitum intake (VA); (4) as per VA, with preferred feed replacing standard feed between 2400 and 0600 h (VA + P). Eight non-lactating dairy cows were used in a 4 × 4 Latin square design. During each experimental period, treatment cows were fed for 7 days, including 3 days habituation and 4 days data collection. Total daily intake was approximately 8% greater (P < 0.001) for the AL and AL + P treatments (23.1 and 22.9 kg DM/cow) as compared with the VA and VA + P treatments (21.6 and 20.9 kg DM/cow). The AL + P and VA treatments had 21% and 90% greater (P < 0.001) dry matter intake (DMI) between 2400 and 0600 h, respectively, compared with the AL treatment. In contrast, the VA + P treatment had similar DMI to the VA treatment. Our experiment shows ability to increase cow feeding activity at night by varying feed type and quantity, though it is possible that a penalty to total DMI may occur using VA. Further research is required to determine if the implementation of variable feed allocation on pasture-based AMS farms is likely to improve milking robot utilisation by increasing cow feeding activity at night.
Open dialogue is an integrative approach to the organisation of specialist mental health services and therapeutic meetings.
This qualitative study sought to explore service users' and clinicians’ experiences of network meetings during the implementation of open dialogue in a modified version, for a UK-based mental health service.
In total 19 participants were interviewed (8 service users and 11 clinicians) and an inductive thematic analysis of the data was conducted.
Four dominant themes were identified: (1) open dialogue delivery, (2) the impact of open dialogue principles; (3) intense interactions and enhanced communication, and (4) organisational challenges. Clinicians considered open dialogue as a preferred, but challenging way of working, while being therapeutic. The data indicated that service users' experiences of network meetings were mixed. There was a wide variety of service user views as to what the purpose of a network meeting was and for some witnessing reflective conversations felt strange. However, the majority described feeling listened to and understood, excluding one service user who described their experience as distressing. Clinicians expressed an authentic self in their interactions with service users and both service users and clinicians described network meetings as emotionally expressive, although this was described as overwhelming at times.
The results of this thematic analysis indicate that service users' and clinicians’ experiences of open dialogue warrant further investigation. The intensity of interactions in network meetings should be carefully considered with service users before gaining consent to commence treatment. Implementation of open dialogue should be monitored to assess clinician- and service-level adherence to the principles of the approach.
The cognitive process of worry, which keeps negative thoughts in mind and elaborates the content, contributes to the occurrence of many mental health disorders. Our principal aim was to develop a straightforward measure of general problematic worry suitable for research and clinical treatment. Our secondary aim was to develop a measure of problematic worry specifically concerning paranoid fears.
An item pool concerning worry in the past month was evaluated in 250 non-clinical individuals and 50 patients with psychosis in a worry treatment trial. Exploratory factor analysis and item response theory (IRT) informed the selection of scale items. IRT analyses were repeated with the scales administered to 273 non-clinical individuals, 79 patients with psychosis and 93 patients with social anxiety disorder. Other clinical measures were administered to assess concurrent validity. Test-retest reliability was assessed with 75 participants. Sensitivity to change was assessed with 43 patients with psychosis.
A 10-item general worry scale (Dunn Worry Questionnaire; DWQ) and a five-item paranoia worry scale (Paranoia Worries Questionnaire; PWQ) were developed. All items were highly discriminative (DWQ a = 1.98–5.03; PWQ a = 4.10–10.7), indicating small increases in latent worry lead to a high probability of item endorsement. The DWQ was highly informative across a wide range of the worry distribution, whilst the PWQ had greatest precision at clinical levels of paranoia worry. The scales demonstrated excellent internal reliability, test-retest reliability, concurrent validity and sensitivity to change.
The new measures of general problematic worry and worry about paranoid fears have excellent psychometric properties.
Local attitudes towards carnivores often reflect the degree of damage they are perceived to cause. Consequently, understanding the interactions between people and these species is essential to conservation efforts. This study investigated local perceptions of three Cerrado canid species and current chicken management practices, to identify the potential damage they cause and how this relates to peoples’ attitudes towards these species. Results from structured interviews at 50 ranches in Goiás, Brazil, highlighted that general knowledge about Cerrado canids differed significantly by species, with interviewees unable to correctly answer questions about the hoary fox Lycalopex vetulus and crab-eating fox Cerdocyon thous in comparison to the maned wolf Chrysocyon brachyurus. Chicken coops were identified as the most effective method for preventing predation, yet only 44% of respondents employed this method. Using a perceived predation measure, interviewees reported chicken predation by all three Cerrado canids even though most of these events were stated to occur during the day, outside the species’ active periods. Reported predation events were a strong predictor of attitude. Participants who experienced predation events reported they did not like having a Cerrado canid on their property. However, 86% of the respondents agreed that Cerrado canids should nevertheless be protected. Our findings support the need to incorporate the human dimension in canid and broader carnivore conservation issues.
Achieving a consistent level of robot utilisation throughout 24 h maximises automatic milking system (AMS) utilisation. However, levels of robot utilisation in the early morning hours are typically low, caused by the diurnal feeding behaviour of cows, limiting the inherent capacity and total production of pasture-based AMS. Our objective was to determine robot utilisation throughout 24 h by dairy cows, based on milking frequency (MF; milking events per animal per day) in a pasture-based AMS. Milking data were collected from January and February 2013 across 56 days, from a single herd of 186 animals (Bos taurus) utilising three Lely A3 robotic milking units, located in Tasmania, Australia. The dairy herd was categorised into three equal sized groups (n=62 per group) according to the cow’s mean daily MF over the duration of the study. Robot utilisation was characterised by an interaction (P< 0.001) between the three MF groups and time of day, with peak milking time for high MF cows within one h of a fresh pasture allocation becoming available, followed by the medium MF and low MF cows 2 and 4 h later, respectively. Cows in the high MF group also presented for milking between 2400 and 0600 h more frequently (77% of nights), compared to the medium MF group (57%) and low MF group (50%). This study has shown the formation of three distinct groups of cows within a herd, based on their MF levels. Further work is required to determine if this finding is replicated across other pasture-based AMS farms.
This school-based study reports on the development and preliminary analysis of the new pictorial semi-structured Child Anxiety and Coping Interview (CACI). Participants included 195 children (Mage = 6.71; SDage = .76) drawn from 29 primary schools located in Western Sydney, Australia. The study used a mixed qualitative and quantitative design. The CACI was used to elicit the children's self-report on their problems, emotions, coping strategies, and coping self-efficacy. Qualitative content and thematic analysis were used to code the children's nominated coping strategies for their problems in the home and school contexts. The top five most common problems reported were as follows: fear of spiders or insects, fear of the dark, going places without parents, doing badly at school, and heights. The top five most common coping strategies reported by the children were support seeking, behavioural avoidance, solving the problem, facing the challenge, and behavioural distraction. Self-reported negative emotional intensity was highest for fear of the dark. Coping self-efficacy for fear of the dark was also high, suggesting the children found their coping strategies helpful, including those that were maladaptive. The clinical implications of these findings are discussed.
This study examined the effects of a school-based cognitive-behavioural group intervention for anxiety in young children, Get Lost Mr Scary, on child self-reported anxiety and coping skills. Participants included 65 children (Mage = 6.50 years, SDage = 0.75) drawn from 13 public primary schools located in Western Sydney, Australia. The children participated in seven weekly 1-hour Get Lost Mr Scary sessions, and their parents attended three information sessions. The pictorial semistructured Child Anxiety and Coping Interview (CACI) was used to elicit the children's self-report of their anxiety symptoms, emotions, coping strategies, and coping efficacy before and after the 7-week intervention. Although children rated their maladaptive coping strategies as helpful, the postintervention results indicated a significant decrease in the use of maladaptive strategies such as behavioural avoidance and an increase in adaptive cognitive strategies, particularly cognitive restructuring. Consistent with parent and teacher reports, child self-reports indicated a significant reduction in anxiety and negative emotional distress. The clinical implications of the findings are discussed.
What Australian psychologists currently learn about specific learning disorders (SLDs) through postgraduate-level training is not clear. Accordingly, the current Australia-wide study analysed 800 postgraduate psychology unit handbook entries to identify which courses teach about SLD and what they teach in this area. Only 2.38% of the identified units explicitly indicated SLD-related content, with 0.38% solely dedicated to SLD content. Descriptive analyses revealed differences in labels used for SLD. Thematic analyses identified five areas of knowledge and skills across SLD units including assessment, intervention, theory and empirical evidence, developmental and cultural awareness and sensitivity, and interpersonal communication. The present findings can inform future refinements to university-level psychology programs across Australia by highlighting the gaps and needs in psychology training.
We present observations of 50 deg2 of the Mopra carbon monoxide (CO) survey of the Southern Galactic Plane, covering Galactic longitudes l = 300–350° and latitudes |b| ⩽ 0.5°. These data have been taken at 0.6 arcmin spatial resolution and 0.1 km s−1spectral resolution, providing an unprecedented view of the molecular clouds and gas of the Southern Galactic Plane in the 109–115 GHz J = 1–0 transitions of 12CO, 13CO, C18O, and C17O.
We present a series of velocity-integrated maps, spectra, and position-velocity plots that illustrate Galactic arm structures and trace masses on the order of ~106 M⊙ deg−2, and include a preliminary catalogue of C18O clumps located between l = 330–340°. Together with the information about the noise statistics of the survey, these data can be retrieved from the Mopra CO website and the PASA data store.
The age-metallicity relation (AMR) is a fundamental observational constraint for understanding how the Galactic disc formed and evolved chemically in time. However, there is not yet an agreement on the observational properties of the AMR, primarily due to the difficulty in obtaining accurate ages for individual field stars. We have started an observational campaign for providing new observational input by using wide white dwarf-main sequence (WDMS) binaries. WDs are natural clocks and can be used to derive accurate ages. Metallicities can be obtained from the MS companions. Since the progenitors of WDs and the MS stars were born at the same time, WDMS provide a unique opportunity to constrain in a robust way the properties of the AMR. We present the AMR derived from analysing a pilot sample of 23 WDMS and provide clear evidence for the lack of correlation between age and metallicity at young and intermediate ages.
Cannabis and tobacco have contrasting cognitive effects. Smoking cannabis with tobacco is prevalent in many countries and although this may well influence cognitive and mental health outcomes, the possibility has rarely been investigated in human experimental psychopharmacological research.
The individual and interactive effects of cannabis and tobacco were evaluated in 24 non-dependent cannabis and tobacco smokers in a randomized, placebo-controlled, double-blind, 2 (cannabis, placebo) × 2 (tobacco, placebo) crossover design. Verbal memory (prose recall), working memory (WM) performance including maintenance, manipulation and attention (N-back), psychotomimetic, subjective and cardiovascular measures were recorded on each of four sessions.
Cannabis alone impaired verbal memory. A priori contrasts indicated that tobacco offset the effects of cannabis on delayed recall. However, this was not supported by linear mixed model analysis. Cannabis load-dependently impaired WM. By contrast, tobacco improved WM across all load levels. The acute psychotomimetic effects and ratings of ‘stoned’ and ‘dizzy’ induced by cannabis were not altered by tobacco. Cannabis and tobacco had independent effects on increasing heart rate and interacting effects on increasing diastolic blood pressure.
Relative to placebo, acute cannabis impaired verbal memory and WM. Tobacco enhanced performance on WM, independently of cannabis. Moreover, we found some preliminary evidence that tobacco may offset the effects of cannabis on delayed, but not immediate, verbal recall. In contrast, the psychotomimetic and subjective effects of cannabis were unaffected by tobacco co-administration. By reducing the cognitive impairment from cannabis, tobacco co-administration may perpetuate use despite adverse health consequences.