Background: The political climate around Cannabis as a medicine is rapidly changing. Legislators are adopting policies regarding appropriate medical applications, while the paucity of research may make policy decisions around conditions for which Cannabis is an effective medicine difficult.

A neuropsychological paradigm is introduced that provides a measure of a bias against disconfirmatory evidence (BADE), and its correspondence with delusions in people with schizophrenia and schizoaffective disorder was investigated. Fifty-two patients diagnosed with schizophrenia or schizoaffective disorder (36 were acutely delusional) and 24 healthy control participants were presented with delusion-neutral pictures in each trial, and were asked to rate the plausibility of four written interpretations of the scenario depicted by that picture. Subsequently, new pictures that provided background information about the depicted scenario were successively presented, and participants were requested to adjust their ratings, taking into account this new information. Two of the interpretations appeared tenable initially but ultimately proved to be implausible, one appeared untenable initially but eventually proved to be plausible, and one appeared untenable at all stages. A BADE was observed for delusional compared to non-delusional patients, as well as for all patients compared to controls. In addition, regardless of symptom profile, patients were more accepting of implausible interpretations than controls. The present work suggests that deficits in reasoning may contribute to the maintenance of delusions via an impairment in the processing of disconfirmatory evidence.

Introduction: Despite known sex differences in the endocannabinoid system of animals, little attention has been paid to sex differences in human's cannabis use patterns and effects. The purpose of the present study was to examine sex differences in cannabis use patterns and effects in a large sample of recreational and medical cannabis users.Methods: A large sample (n=2374) of cannabis users completed an anonymous, online survey that assessed their cannabis use practices and experiences, including the short-term acute effects of cannabis and withdrawal effects. A subsample of 1418 medical cannabis users further indicated the medical conditions for which they use cannabis and its perceived efficacy.Results: The results indicated that men reported using cannabis more frequently and in higher quantities than did women. Men were more likely to report using joints/blunts, vaporizers, and concentrates, while women were more likely to report using pipes and oral administration. Men were more likely than women to report increased appetite, improved memory, enthusiasm, altered time perception, and increased musicality when high, while women were more likely than men to report loss of appetite and desire to clean when high. Men were more likely than women to report insomnia and vivid dreams during periods of withdrawal, while women were more likely than men to report nausea and anxiety as withdrawal symptoms. Sex differences in the conditions for which medical cannabis is used, and its efficacy, were trivial.Conclusions: These results may be used to focus research on biological and psychosocial mechanisms underlying cannabis-related sex differences, to inform clinicians treating individuals with cannabis use disorders, and to inform cannabis consumers, clinicians, and policymakers about the risks and benefits of cannabis for both sexes.

ObjectiveWe created the Daily Sessions, Frequency, Age of Onset, and Quantity of Cannabis Use Inventory (DFAQ-CU) because the current lack of psychometrically sound inventories for measuring these dimensions of cannabis use has impeded research on the effects of cannabis in humans.MethodA sample of 2,062 cannabis users completed the DFAQ-CU and was used to assess the DFAQ-CU’s factor structure and reliability. To assess validity, a subsample of 645 participants completed additional measures of cannabis dependence and problems (Marijuana Smoking History Questionnaire [MSHQ], Timeline Followback [TLFB], Cannabis Abuse Screening Test [CAST], Cannabis Use Disorders Identification Test Revised [CUDIT-R], Cannabis Use Problems Identification Test [CUPIT], and Alcohol Use Disorder Identification Test [AUDIT]).ResultsA six-factor structure was revealed, with factors measuring: daily sessions, frequency, age of onset, marijuana quantity, cannabis concentrate quantity, and edibles quantity. The factors were reliable, with Cronbach’s alpha coefficients ranging from .69 (daily sessions) to .95 (frequency). Results further provided evidence for the factors’ convergent (MSHQ, TLFB), predictive (CAST, CUDIT-R, CUPIT), and discriminant validity (AUDIT).ConclusionsThe DFAQ-CU is the first psychometrically sound inventory for measuring frequency, age of onset, and quantity of cannabis use. It contains pictures of marijuana to facilitate the measurement of quantity of marijuana used, as well as questions to assess the use of different forms of cannabis (e.g., concentrates, edibles), methods of administering cannabis (e.g., joints, hand pipes, vaporizers), and typical THC levels. As such, the DFAQ-CU should help facilitate research on frequency, quantity, and age of onset of cannabis use.

Do interindividual differences in prospective memory task performance reflect individual differences in personality and lifestyle? Do the cognitive abilities known to change with age retain their power to predict episodic prospective memory task performance after controlling for personality and lifestyle variables, and do personality and lifestyle variables offer predictive power apart from that provided by cognitive ability measures? To answer these questions, we conducted a study with community-living healthy individuals (n= 141) between 18 and 81 years of age. They completed three different episodic prospective memory tasks--two laboratory tasks and one field task--as well as various measures of personality, lifestyle, and cognitive ability. The results indicated that personality and lifestyle reliably predicted who will succeed and who will fail on all three episodic prospective memory tasks. Conscientiousness predicted performance on two of the prospective memory tasks; socially prescribed perfectionism and neuroticism each predicted performance on one of the prospective memory tasks. Cognitive ability predicted performance on one of the laboratory prospective memory tasks but not on the other two prospective memory tasks. After we controlled for individual differences in personality and lifestyle variables, cognitive ability was no longer able to predict performance on the laboratory prospective memory task. By contrast, controlling for cognitive ability had no influence on the predictive power of the personality and lifestyle variables.

In prior studies, it was observed that patients with schizophrenia show abnormally high knowledge corruption (i.e., high-confident errors expressed as a percentage of all high-confident responses were increased for schizophrenic patients relative to controls). The authors examined the conditions under which excessive knowledge corruption occurred using the Deese-Roediger-McDermott paradigm. Whereas knowledge corruption in schizophrenia was significantly greater for false-negative errors relative to controls, no group difference occurred for false-positive errors. The groups showed a comparable high degree of confidence for false-positive recognition of critical lure items. Similar to findings collected in elderly participants, patients, but not controls, showed a strong positive correlation between the number of recognized studied items and false-positive recognition of the critical lure.Memory dysfunctions have been ascribed a key role in many pathogenetic models of schizophrenia (e.g., Hemsley, 1994). The literature suggests that both memory recall and recognition are severely compromised in schizophrenic patients relative to healthy participants (see Aleman, Hijman, de Haan, & Kahn, 1999, for a meta-analysis; see also Heinrichs & Zakzanis, 1998). However, as of yet, no schizophrenia-specific mnestic aberration has been identified. In contrast to an extensive body of research on forgetting in schizophrenia (i.e., false-negative errors), until recently the investigation of false-positive errors has attracted little attention. Depending on the paradigm used, some studies have provided evidence for enhanced false-positive memory errors in schizophrenia (Stirling, Hellewell, & Hewitt, 1997), whereas others have been unable to detect any group differences (e.g., Brébion, Amador, Smith, & Gorman, 1997;Moritz, Heeren, Andresen, & Krausz, 2001). Weiss, Dodson, Goff, Schacter, and Heckers (2002) have suggested that task demands and material may represent moderators for these inconsistent findings. In this study, increased false recognition in schizophrenia was evident for word, but not picture, material and only occurred in an experimental condition in which correct task performance necessitated retrieval of item-specific information (i.e., recollection of an item's spatial and temporal context).Another neglected area of memory research in schizophrenia is the investigation of memory confidence. In two source-monitoring studies Moritz, Woodward, & Ruff, 2003), evidence for a dissociation between objective and subjective memory performance in schizophrenia was found (i.e., measured performance accuracy vs. subjective evaluation of one's performance). Results from both investigations support the claim that patients with schizophrenia, irrespective of psychopathological status, display an enhanced confidence for false memory responses relative to healthy controls, whereas no group differences occurred for confidence in correct decisions. In the second study , 12% of responses made by schizophrenic patients with high confi...

Recent trends in cannabis legalization have increased the necessity to better understand the effects of cannabis use. Animal models involving traditional cannabinoid self-administration approaches have been notoriously difficult to establish and differences in the drug used and its route of administration have limited the translational value of preclinical studies. To address this challenge in the field, we have developed a novel method of cannabis self-administration using response-contingent delivery of vaporized ⌬ 9-tetrahydrocannabinol-rich (CAN THC) or cannabidiol-rich (CAN CBD) whole-plant cannabis extracts. Male Sprague-Dawley rats were trained to nose-poke for discrete puffs of CAN THC , CAN CBD , or vehicle (VEH) in daily 1 h sessions. Cannabis vapor reinforcement resulted in strong discrimination between active and inactive operanda. CAN THC maintained higher response rates under fixed ratio schedules and higher break points under progressive ratio schedules compared with CAN CBD or VEH, and the number of vapor deliveries positively correlated with plasma THC concentrations. Moreover, metabolic phenotyping studies revealed alterations in locomotor activity, energy expenditure, and daily food intake that are consistent with effects in human cannabis users. Furthermore, both cannabis regimens produced ecologically relevant brain concentrations of THC and CBD and CAN THC administration decreased hippocampal CB1 receptor binding. Removal of CAN THC reinforcement (but not CAN CBD) resulted in a robust extinction burst and an increase in cue-induced cannabis-seeking behavior relative to VEH. These data indicate that volitional exposure to THC-rich cannabis vapor has bona fide reinforcing properties and collectively support the utility of the vapor self-administration model for the preclinical assessment of volitional cannabis intake and cannabis-seeking behaviors.

In two previous studies, it was observed that schizophrenic patients display increased confidence in memory errors compared with controls. The patient group displayed an increased proportion of errors in their knowledge system, quantified as the percentage of high-confident responses that are errors. The latter phenomenon has been termed knowledge corruption and is put forward as a risk factor for the emergence of delusions. In the present study, knowledge corruption was analyzed separately for different aspects of memory errors. A source-monitoring task was used, for which participants (30 schizophrenic patients with past or current paranoid ideas and 15 healthy controls) were asked to provide associates for each of 20 prime words. Later, participants were required to recognize studied words among distractor words, judge the original source, and provide a confidence rating for the most recent decision. Schizophrenic patients displayed greater confidence in memory errors compared with controls. Knowledge corruption was observed to be significantly greater in schizophrenic patients relative to controls for false-positive and false-negative judgments. It is proposed that reliance on false knowledge represents a candidate mechanism for the emergence of fixed false beliefs (i.e., delusions).