U-shaped curve of psychosis according to cannabis use: New evidence from a snowball sample

Characterization of Cannabis users and products and the experience of negative mental emotions following Cannabis use

There is a potential link between cannabis and mental disorders. Cannabis exposure involves in many cases negative mental emotions, which are unpleasant sensations or thoughts. Whereas mild cases of negative mental emotions inflict patient's quality of life, more severe cases lead to therapy discontinuations, or even hospitalizations and death. This study characterizes cannabis users who experienced negative mental emotions after cannabis exposure. The Releaf App database was utilized to evaluate the association between personal and cannabis use characteristics on reporting a negative mental emotion during cannabis exposure. This global mobile lets individuals track real-time cannabis experience use with cannabinoid-based products, containing data points such as gender, age, reasons for use, product type, cannabis composition, and feelings and emotions experienced after cannabis use. Multivariable logistic regression models were constructed, adjusting for potential confounders such as gender and previous experience with cannabis use. The study population comprised 4,435 users, and 34,279 sessions were collected from various countries, mainly from North America, and included in the primary analysis. Reporting on negative mental emotions was associated with users in the age group of 18-30 years. Using cannabis for a mental purpose was associated with a small increase in reporting on negative mental emotions (OR = 1.10, 95%CI [1.03-1.19]). Oral products were associated with reporting on negative mental emotions. THC-dominant products were associated with reporting negative mental emotions compared to balanced products (OR = 1.21, 95%CI [1.06-1.38]). This study suggests that some characteristics of cannabis use, such as young age and oral consumption are associated with negative mental emotions. Further studies should examine the interface between cannabis consumption, characteristics of consumers, and negative emotional experience or even long-term mental disorders.

Impaired motor cortical plasticity associated with cannabis use disorder in young adults

Maladaptive cortical plasticity has been described in individuals with heroin and methamphetamine addiction and may mediate other substance abuse disorders. It is unknown whether cannabis dependence in humans alters the capacity for induction of cortical plasticity. The aim of this study was to non-invasively investigate cortical plasticity with transcranial magnetic stimulation in young adults who meet DSM-5 criteria for cannabis use disorder (CUD). Thirty men (ages 20- 30) who used cannabis daily over the previous 6 months (15 diagnosed of CUD) and 15 demographically matched non-users were enrolled in this study. All participants underwent two sessions of theta burst stimulation (TBS) in which either continuous TBS (cTBS; 600 pulses, 80% active motor threshold) or intermittent TBS (iTBS; 2-s train of cTBS repeated every 10 s for a total of 190 s, 600 pulses) was applied over the primary motor cortex. The effects of these protocols were assessed by analysing the contralateral motor evoked potentials (MEPs). The relationships between cortical plasticity and problematic cannabis use, degree of dependence, and nicotine addiction were also investigated. Significant MEP inhibition after cTBS was observed in both cannabis users without CUD and non-users, while this inhibition was not seen in cannabis users with CUD. Strikingly, less motor cortical plasticity was observed in subjects with severe problematic cannabis use. No significant differences between users and non-users were found in the iTBS-induced cortical plasticity measures. Our study provides the first evidence of maladaptive cortical plasticity associated with cannabis use disorder and problematic cannabis use in humans.

Does cannabis use predict psychometric schizotypy via aberrant salience?

Cannabis can induce acute psychotic symptoms in healthy individuals and exacerbate pre-existing psychotic symptoms in patients with schizophrenia. Inappropriate salience allocation is hypothesised to be central to the association between dopamine dysregulation and psychotic symptoms. This study examined whether cannabis use is associated with self-reported salience dysfunction and schizotypal symptoms in a non-clinical population. 910 University students completed the following questionnaire battery: the cannabis experience questionnaire modified version (CEQmv); schizotypal personality questionnaire (SPQ); community assessment of psychic experience (CAPE); aberrant salience inventory (ASI). Mediation analysis was used to test whether aberrant salience mediated the relationship between cannabis use and schizotypal traits. Both frequent cannabis consumption during the previous year and ASI score predicted variation across selected positive and disorganised SPQ subscales. However, for the SPQ subscales 'ideas of reference' and 'odd beliefs', mediation analysis revealed that with the addition of ASI score as a mediating variable, current cannabis use no longer predicted scores on these subscales. Similarly, cannabis use frequency predicted higher total SPQ as well as specific Positive and Disorganised subscale scores, but ASI score as a mediating variable removed the significant predictive relationship between frequent cannabis use and 'odd beliefs', 'ideas of reference', 'unusual perceptual experiences', 'odd speech', and total SPQ scores. In summary, cannabis use was associated with increased psychometric schizotypy and aberrant salience. Using self-report measures in a non-clinical population, the cannabis-related increase in selected positive and disorganised SPQ subscale scores was shown to be, at least in part, mediated by disturbance in salience processing mechanisms.

Trends of major depressive episode among people with cannabis use: Findings from the National Survey on Drug Use and Health 2006-2015

Background: A dose-response association, suggesting that heavy cannabis users are more likely to report depressive disorders, has been hypothesized. However, evidence is not conclusive, and we aimed at testing the existence of a linear association between different levels of cannabis use and depressive disorders using large, representative, repeated surveys. Methods: We examined prevalence rates of different levels of past-year cannabis use and major depressive episode (MDE), separately for young people (12-17 years) and adults (18-64 years), using data between 2006 and 2015 from the National Survey on Drug Use and Health. Prevalence rates estimates with 95% confidence intervals were computed, and the association between past-year MDE and cannabis use was assessed. We then investigated whether time-period trends existed for MDE and, if so, whether these differed by cannabis use levels. Models included both time period, to evaluate trend changes in past-year MDE from 2006 to 2015, and time period by cannabis level interaction terms. Results: Cannabis users were more likely, using both single-year and pooled survey data, to have suffered from MDE in the past year. Multiple logistic regression models, after adjusting for time period, age, and gender, showed an association between MDE and cannabis use, regardless of its levels. However, a roughly dose-response relationship was detectable only for adults. Trends in past-year MDE prevalence rates among subjects with different levels of cannabis use did not differ from trends among nonusers. Women were more likely to report concurrent past-year MDE and cannabis use than men. Conclusions: Cannabis users have consistently higher prevalence rates of depressive disorders compared with nonusers, suggesting the need for integrated screening and treatment programs to tackle this comorbid condition.

Cannabis use as a risk factor for psychotic-like experiences: A systematic review of non-clinical populations evaluated with the Community Assessment of Psychic Experiences

AIM

Epidemiological data have provided evidence that psychotic-like experiences (PLEs) can occur in the general population, not necessarily accompanied by the impairment and suffering observed in formal psychiatric diagnoses. According to the psychosis continuum hypothesis, PLEs would be subject to the same risk factors as frank psychosis. The aim of this review was to summarize observational studies that evaluated cannabis use as a risk factor for PLEs as determined by the Community Assessment of Psychic Experiences in non-clinical samples. The instrument composed of 3 dimensions-positive, negative and depressive-is a scale specifically designed to assess the occurrence, frequency and impact of PLEs in non-clinical population.

METHODS

We searched PubMed/Medline, Web of Science and PsycInfo electronic databases for indexed peer-reviewed studies published until September 2017.

RESULTS

We initially identified 100 articles. The PRISMA model for systematic reviews was used and 19 full-text articles were analysed. In general, the findings suggested that the higher the cannabis use and the younger the participants, the higher the reports of PLEs, although associations were more consistent for the positive dimension.

CONCLUSIONS

More attention should be paid to the understanding of the risk factors of PLEs in the general population, since these experiences are themselves a risk for psychotic disorders.