Carrie Cuttler

The Contribution of a Cognitive Bias Against Disconfirmatory Evidence (BADE) to Delusions in Schizophrenia

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. The authors thank Jessica Bristowe, Jannine Laseleta, and Tonya Kragelj for assistance with data collection and data management, and Drs. Karin Christensen, Mahesh Menon, Elton Ngan, Eric Strachan, and Ivan Torres for comments and discussions that shaped this work. This research was supported by post-doctoral fellowships from the Mind Foundation of BC, the Canadian Psychiatric Research Foundation, and the Canadian Institutes of Health Research to TSW, scholarships from the German Academic Exchange Program (DAAD) to SM, and a grant from the Riverview Hospital Academic Steering Committee to TSW.

Confidence in Errors as a Possible Basis for Delusions in Schizophrenia

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).

False Memories in Schizophrenia.

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.

Everyday Life Memory Deficits in Pregnant Women

Converging evidence indicates that pregnant women report experiencing problems with memory, but the results of studies using objective measures are ambiguous. The present study investigated potential reason(s) for the discrepancy between findings of subjective and objective memory deficits, as well as potential source(s) of pregnant womens problems with memory. Sixty-one pregnant and 24 nonpregnant women completed a series of memory tests which included field and laboratory measures of prospective memory. Three standardized questionnaires were used to assess subjective aspects of memory. The influence of cortisol, depressed mood, anxiety, physical symptoms, sleep/fatigue, and busyness on pregnancy-related deficits was also examined. The findings revealed objective pregnancy-related deficits on two of the field measures of prospective memory. Pregnancy-related subjective deficits were also detected on all of the questionnaires. In contrast, no objective pregnancy-related deficits were found on the laboratory measures of memory. Increased physical symptoms accounted for one of the objective deficits in memory, while depressed mood and physical symptoms accounted for two of the subjective memory deficits. Collectively, these findings suggest that pregnant women experience everyday life problems with memory that are not readily detected in the laboratory environment. The predominant use of laboratory tests may explain the myriad of previous failures to detect objective deficits in pregnant womens memory.

Checking-in on the memory deficit and meta-memory deficit theories of compulsive checking.

The memory deficit theory and meta-memory deficit theory provide intuitive accounts for checking compulsions. According to these theories, deficits in memory and/or a lack of confidence in memory contribute to the compulsion to check. Our goal was to examine whether, as predicted by the theories, memory deficits and/or meta-memory deficits are unique to individuals with checking compulsions as opposed to being common to all OCD patients. The review revealed that previous investigations of these theories have focused almost exclusively on retrospective memory. More importantly, results of the review revealed similar patterns of deficits in the retrospective memory performance and meta-memory scores of OCD checkers and OCD non-checkers, indicating that deficits in retrospective memory are not unique to checkers and therefore are unlikely to contribute to the compulsion to check. The review also features results of the few studies that have examined the theories in the context of prospective memory, and it provides the results of some supplementary analyses which show that checkers demonstrate unique memory and meta-memory deficits related to prospective memory. Together these results indicate that the memory deficit and meta-memory deficit theories should be re-conceptualized and further examined in the context of prospective memory.

Diminished confidence in prospective memory causes doubts and urges to check

BACKGROUND AND OBJECTIVES Correlational research has demonstrated links between prospective memory and checking compulsions. These findings suggest that negative beliefs and diminished confidence in prospective memory may contribute to intrusive doubts that tasks were not completed and ultimately to checking behavior. The present study represents the first experimental test of the hypothesis that diminished confidence in prospective memory causes increased doubt and urges to check. METHODS Participants completed several tests and questionnaires assessing prospective memory. Participants were randomly assigned to receive either false positive or false negative feedback about their prospective memory. They subsequently completed additional prospective memory tests and their doubts and urges to check that each of those tests was properly performed were assessed. RESULTS Participants who received false negative feedback about their prospective memory reported significantly higher levels of doubt and urges to check compared to those who received false positive feedback. LIMITATIONS A non-clinical sample was used and participants with severe levels of depression and anxiety were excused before the feedback phase to avoid causing them further distress. CONCLUSIONS The results provide further support for memory confidence models of checking compulsions by indicating that diminished confidence in prospective memory can cause increased doubt and urges to check.

Mechanisms Underlying the Link between Cannabis Use and Prospective Memory

While the effects of cannabis use on retrospective memory have been extensively examined, only a limited number of studies have focused on the links between cannabis use and prospective memory. We conducted two studies to examine the links between cannabis use and both time-based and event-based prospective memory as well as potential mechanisms underlying these links. For the first study, 805 students completed an online survey designed to assess cannabis consumption, problems with cannabis use indicative of a disorder, and frequency of experiencing prospective memory failures. The results showed small to moderate sized correlations between cannabis consumption, problems with cannabis use, and prospective memory. However, a series of mediation analyses revealed that correlations between problems with cannabis use and prospective memory were driven by self-reported problems with retrospective memory. For the second study, 48 non-users (who had never used cannabis), 48 experimenters (who had used cannabis five or fewer times in their lives), and 48 chronic users (who had used cannabis at least three times a week for one year) were administered three objective prospective memory tests and three self-report measures of prospective memory. The results revealed no objective deficits in prospective memory associated with chronic cannabis use. In contrast, chronic cannabis users reported experiencing more internally-cued prospective memory failures. Subsequent analyses revealed that this effect was driven by self-reported problems with retrospective memory as well as by use of alcohol and other drugs. Although our samples were not fully characterized with respect to variables such as neurological disorders and family history of substance use disorders, leaving open the possibility that these variables may play a role in the detected relationships, the present findings indicate that cannabis use has a modest effect on self-reported problems with prospective memory, with a primary problem with retrospective memory appearing to underlie this relationship.

Blunted stress reactivity in chronic cannabis users

RationaleOne of the most commonly cited reasons for chronic cannabis use is to cope with stress. Consistent with this, cannabis users have shown reduced emotional arousal and dampened stress reactivity in response to negative imagery.ObjectivesTo our knowledge, the present study represents the first to examine the effects of an acute stress manipulation on subjective stress and salivary cortisol in chronic cannabis users compared to non-users.MethodsForty cannabis users and 42 non-users were randomly assigned to complete either the stress or no stress conditions of the Maastricht Acute Stress Test (MAST). The stress condition of the MAST manipulates both physiological (placing hand in ice bath) and psychosocial stress (performing math under conditions of social evaluation). Participants gave baseline subjective stress ratings before, during, and after the stress manipulation. Cortisol was measured from saliva samples obtained before and after the stress manipulation. Further, cannabis cravings and symptoms of withdrawal were measured.ResultsSubjective stress ratings and cortisol levels were significantly higher in non-users in the stress condition relative to non-users in the no stress condition. In contrast, cannabis users demonstrated blunted stress reactivity; specifically, they showed no increase in cortisol and a significantly smaller increase in subjective stress ratings. The stress manipulation had no impact on cannabis users’ self-reported cravings or withdrawal symptoms.ConclusionChronic cannabis use is associated with blunted stress reactivity. Future research is needed to determine whether this helps to confer resiliency or vulnerability to stress-related psychopathology as well as the mechanisms underlying this effect.

Measuring cannabis consumption: Psychometric properties of the Daily Sessions, Frequency, Age of Onset, and Quantity of Cannabis Use Inventory (DFAQ-CU)

Objective We 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. Method A 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]). Results A 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). Conclusions The 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.

Did I Forget to Lock the Door? The Link between Prospective Memory Failures and Doubt in the Compulsion to Check

Previous research has demonstrated links between prospective memory failures and checking compulsions. The findings suggest that experiences with prospective memory failures may contribute to the intrusive doubts that tasks were not completed that instigate checking compulsions. However, the link between prospective memory and intrusive doubts has yet to be empirically investigated. Accordingly, the present study focused on examining whether prospective memory failures are related to doubting, as well as whether doubting mediates the relationship between prospective memory and checking compulsions. Undergraduate students completed self-report measures of checking compulsions, doubting, prospective memory and retrospective memory. Participants also completed objective tests of prospective memory and retrospective memory. Prospective memory failures and excessive doubting showed consistent correlations. Two of three objective tests of prospective memory and one of two measures of confidence in performance on prospective memory tests showed significant correlations with checking. Tests of mediation showed that the links between checking compulsions, objective prospective memory test failures and confidence in prospective memory performance were mediated by doubting. The results thereby supported the hypothesis that experiences with prospective memory failures contribute to the intrusive doubts that instigate checking.