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.

As new cannabis products and administration methods proliferate, patterns of use are becoming increasingly heterogeneous. However, few studies have explored different profiles of cannabis use and their association with problematic use.

Latent class analysis (LCA) was used to identify subgroups of past-year cannabis users endorsing distinct patterns of use from a large international sample (n = 55 240). Past-12-months use of six different cannabis types (sinsemilla, herbal, hashish, concentrates, kief, edibles) were used as latent class indicators. Participants also reported the frequency and amount of cannabis used, whether they had ever received a mental health disorder diagnosis and their cannabis dependence severity via the Severity of Dependence Scale (SDS).

LCA identified seven distinct classes of cannabis use, characterised by high probabilities of using: sinsemilla & herbal (30.3% of the sample); sinsemilla, herbal & hashish (20.4%); herbal (18.4%); hashish & herbal (18.8%); all types (5.7%); edibles & herbal (4.6%) and concentrates & sinsemilla (1.7%). Relative to the herbal class, classes characterised by sinsemilla and/or hashish use had increased dependence severity. By contrast, the classes characterised by concentrates use did not show strong associations with cannabis dependence but reported greater rates of ever receiving a mental health disorder diagnosis.

The identification of these distinct classes underscores heterogeneity among cannabis use behaviours and provides novel insight into their different associations with addiction and mental health.

The number of people entering specialist drug treatment for cannabis problems has increased considerably in recent years. The reasons for this are unclear, but rising cannabis potency could be a contributing factor.

Cannabis potency data were obtained from an ongoing monitoring programme in the Netherlands. We analysed concentrations of δ-9-tetrahydrocannabinol (THC) from the most popular variety of domestic herbal cannabis sold in each retail outlet (2000–2015). Mixed effects linear regression models examined time-dependent associations between THC and first-time cannabis admissions to specialist drug treatment. Candidate time lags were 0–10 years, based on normative European drug treatment data.

THC increased from a mean (95% CI) of 8.62 (7.97–9.27) to 20.38 (19.09–21.67) from 2000 to 2004 and then decreased to 15.31 (14.24–16.38) in 2015. First-time cannabis admissions (per 100 000 inhabitants) rose from 7.08 to 26.36 from 2000 to 2010, and then decreased to 19.82 in 2015. THC was positively associated with treatment entry at lags of 0–9 years, with the strongest association at 5 years, b = 0.370 (0.317–0.424), p < 0.0001. After adjusting for age, sex and non-cannabis drug treatment admissions, these positive associations were attenuated but remained statistically significant at lags of 5–7 years and were again strongest at 5 years, b = 0.082 (0.052–0.111), p < 0.0001.

In this 16-year observational study, we found positive time-dependent associations between changes in cannabis potency and first-time cannabis admissions to drug treatment. These associations are biologically plausible, but their strength after adjustment suggests that other factors are also important.

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.

Cannabis is a widely used drug associated with increased risk for psychosis. The dopamine hypothesis of psychosis postulates that altered salience processing leads to psychosis. We therefore tested the hypothesis that cannabis users exhibit aberrant salience and explored the relationship between aberrant salience and dopamine synthesis capacity.

We tested 17 cannabis users and 17 age- and sex-matched non-user controls using the Salience Attribution Test, a probabilistic reward-learning task. Within users, cannabis-induced psychotic symptoms were measured with the Psychotomimetic States Inventory. Dopamine synthesis capacity, indexed as the influx rate constant K i cer, was measured in 10 users and six controls with 3,4-dihydroxy-6-[18F]fluoro-l-phenylalanine positron emission tomography.

There was no significant difference in aberrant salience between the groups [F1,32 = 1.12, p = 0.30 (implicit); F1,32 = 1.09, p = 0.30 (explicit)]. Within users there was a significant positive relationship between cannabis-induced psychotic symptom severity and explicit aberrant salience scores (r = 0.61, p = 0.04) and there was a significant association between cannabis dependency/abuse status and high implicit aberrant salience scores (F1,15 = 5.8, p = 0.03). Within controls, implicit aberrant salience was inversely correlated with whole striatal dopamine synthesis capacity (r = −0.91, p = 0.01), whereas this relationship was non-significant within users (difference between correlations: Z = −2.05, p = 0.04).

Aberrant salience is positively associated with cannabis-induced psychotic symptom severity, but is not seen in cannabis users overall. This is consistent with the hypothesis that the link between cannabis use and psychosis involves alterations in salience processing. Longitudinal studies are needed to determine whether these cognitive abnormalities are pre-existing or caused by long-term cannabis use.

Post-traumatic stress disorder (PTSD) involves maladaptive long-term memory formation which underlies involuntary intrusive thoughts about the trauma. Preventing the development of such maladaptive memory is a key aim in preventing the development of PTSD. We examined whether the N-methyl d-aspartate receptor (NMDAR) antagonist gas nitrous oxide (N2O) could reduce the frequency of intrusive memories by inhibiting NMDAR-dependent memory consolidation in a laboratory analogue of psychological trauma.

Participants were randomized to inhale N2O (N = 25) or medical air (N = 25) after viewing a negatively valenced emotional film clip (‘trauma film’). Participants subsequently completed a daily diary assessing frequency of intrusive thoughts relating to the film clip. A week later, participants completed an explicit memory recall task related to the film.

Post-encoding N2O sped the reduction in intrusive memory frequency, with a significant reduction by the next day in the N2O group compared to 4 days later in the air group. N2O also interacted with post-film dissociation, producing increased intrusion frequency in those who were highly dissociated at baseline. Sleep length and quality the night after viewing the film did not differ between the groups.

N2O speeds the reduction of intrusive analogue trauma memory in a time-dependent manner, consistent with sleep-dependent long-term consolidation disruption. Further research with this drug is warranted to determine its potential to inoculate against enduring effects of psychological trauma; however, caution is also urged in dissociated individuals where N2O may aggravate PTSD-like symptomatology.

Cannabis use is decreasing in England and Wales, while demand for cannabis treatment in addiction services continues to rise. This could be partly due to an increased availability of high-potency cannabis.

Adults residing in the UK were questioned about their drug use, including three types of cannabis (high potency: skunk; low potency: other grass, resin). Cannabis types were profiled and examined for possible associations between frequency of use and (i) cannabis dependence, (ii) cannabis-related concerns.

Frequent use of high-potency cannabis predicted a greater severity of dependence [days of skunk use per month: b = 0.254, 95% confidence interval (CI) 0.161–0.357, p < 0.001] and this effect became stronger as age decreased (b = −0.006, 95% CI −0.010 to −0.002, p = 0.004). By contrast, use of low-potency cannabis was not associated with dependence (days of other grass use per month: b = 0.020, 95% CI −0.029 to 0.070, p = 0.436; days of resin use per month: b = 0.025, 95% CI −0.019 to 0.067, p = 0.245). Frequency of cannabis use (all types) did not predict severity of cannabis-related concerns. High-potency cannabis was clearly distinct from low-potency varieties by its marked effects on memory and paranoia. It also produced the best high, was preferred, and most available.

High-potency cannabis use is associated with an increased severity of dependence, especially in young people. Its profile is strongly defined by negative effects (memory, paranoia), but also positive characteristics (best high, preferred type), which may be important when considering clinical or public health interventions focusing on cannabis potency.

To systematically summarise the peer-reviewed literature relating to the aetiology, clinical presentation, investigation and treatment of geniculate neuralgia.

Articles published in English between 1932 and 2012, identified using Medline, Embase and Cochrane databases.

The search terms ‘geniculate neuralgia’, ‘nervus intermedius neuralgia’, ‘facial pain’, ‘otalgia’ and ‘neuralgia’ were used to identify relevant papers.

Fewer than 150 reported cases were published in English between 1932 and 2012. The aetiology of the condition remains unknown, and clinical presentation varies. Non-neuralgic causes of otalgia should always be excluded by a thorough clinical examination, audiological assessment and radiological investigations before making a diagnosis of geniculate neuralgia. Conservative medical treatment is always the first-line therapy. Surgical treatment should be offered if medical treatment fails. The two commonest surgical options are transection of the nervus intermedius, and microvascular decompression of the nerve at the nerve root entry zone of the brainstem. However, extracranial intratemporal division of the cutaneous branches of the facial nerve may offer a safer and similarly effective treatment.

The response to medical treatment for this condition varies between individuals. The long-term outcomes of surgery remain unknown because of limited data.

Smoking is highly prevalent in people diagnosed with schizophrenia, but the reason for this co-morbidity is currently unclear. One possible explanation is that a common abnormality underpins the development of psychosis and independently enhances the incentive motivational properties of drugs and their associated cues. This study aimed to investigate whether incentive salience attribution towards smoking cues, as assessed by attentional bias, is heightened in schizophrenia and associated with delusions and hallucinations.

Twenty-two smokers diagnosed with schizophrenia and 23 control smokers were assessed for smoking-related attentional bias using a modified Stroop task. Craving, nicotine dependence, smoking behaviour and positive and negative symptoms of schizophrenia were also recorded.

Both groups showed similar craving scores and smoking behaviour according to self-report and expired carbon monoxide (CO), although the patient group had higher nicotine dependence scores. Attentional bias, as evidenced by significant interference from smoking-related words on the modified Stroop task, was similar in both groups and correlated with CO levels. Attentional bias was positively related to severity of delusions but not hallucinations or other symptoms in the schizophrenia group.

This study supports the hypothesis that the development of delusions and the incentive motivational aspects of smoking may share a common biological substrate. These findings may offer some explanation for the elevated rates of smoking and other drug use in people with psychotic illness.