For those of us suffering with bipolar disorder and want to know if marijuana, were out of luck on information, because as this article states no studies have been done Ringen, P. A., Vaskinn, A., Sundet, K., Engh, J. A., Jónsdóttir, H., Simonsen, C., . . . Andreassen, O. A. (2010). Opposite relationships between cannabis use and neurocognitive functioning in bipolar disorder and schizophrenia. Psychological Medicine, 40(8), 1337-47. doi:dx.doi.org/10.1017/S0033291709991620 ssage you soon. Abstract (summary) Translate Abstract Background: Cannabis use is associated with altered neurocognitive functioning in severe mental disorders, but data are still inconclusive and there are no studies of bipolar disorder. The aim of this study was to investigate the association between cannabis use and neurocognition in bipolar disorder compared with schizophrenia in a naturalistic setting. Method: A total of 133 patients with bipolar disorder and 140 patients with schizophrenia underwent neuropsychological assessments and clinical characterization including measures of substance use. Relationships between cannabis users and neurocognitive function were explored in the two diagnostic groups. Possible interactions between diagnosis and cannabis use were investigated, and findings were controlled for possible confounders. Results: In bipolar disorder subjects, cannabis use was associated with better neurocognitive function, but the opposite was the case for the schizophrenia subjects. There was a statistically significant interaction effect of diagnosis and cannabis use on focused attention (p=0.019), executive functioning (verbal fluency - set shifting) (p=0.009), logical memory-learning (p=0.007) and on logical memory-recall (p=0.004). These differences in neurocognitive function could not be explained by putative confounders. Conclusions: The findings suggest that cannabis use may be related to improved neurocognition in bipolar disorder and compromised neurocognition in schizophrenia. The results need to be replicated in independent samples, and may suggest different underlying disease mechanisms in the two disorders. [PUBLICATION ABSTRACT] Introduction Cognitive deficits are common in both schizophrenia and bipolar disorder (Keefe et al. 2006; Martinez-Aran et al. 2007; Simonsen et al. 2008). Substance use is also highly prevalent in both disorders, especially of cannabis (Kavanagh et al. 2004; Green et al. 2005; Murray et al. 2007). Although cannabis is reported to affect neurocognition in healthy individuals (Ilan et al. 2004; Ranganathan & DSouza, 2006), there are few studies of cannabis use in relation to neuropsychological test performance in schizophrenia, and to our knowledge there are no studies investigating this association in bipolar disorder. The only existing study of a combined sample of schizophrenia and bipolar disorder found no clear associations between cannabis use and neurocognition (Liraud & Verdoux, 2002). Carey et al. (2003) reported that dual-diagnosis patients with schizophrenia or bipolar disorder performed better on non-verbal neuropsychological tests than those who never abused. Studies of general substance use in schizophrenia spectrum disorder patients showed diverging results (Joyal et al. 2003; Herman, 2004; Thoma et al. 2007; Wobrock et al. 2007; Potvin et al. 2008; van Os et al. 2009). In the only intervention study, administration of [Delta]9-tetrahydrocannabinol (THC) to patients with schizophrenia was followed by a temporary reduction in verbal learning and memory (DSouza et al. 2005). The few existing clinical studies of cannabis use, however, have mainly shown equal or better cognitive functioning in cannabis users with schizophrenia compared with abstainers (Coulston et al. 2007a, b; Potvin et al. 2008). A continuum of traits between the diagnostic groups of schizophrenia and bipolar disorder rather than distinct categories is proposed in the mood-psychosis spectrum continuum model (Craddock & Owen, 2007; van Os et al. 2009). Findings of milder neurocognitive deficits in bipolar disorder than in schizophrenia (Cahill et al. 2006; Daban et al. 2006; Simonsen et al. 2009) and less neurocognitive dysfunction in bipolar II than bipolar I disorder (Simonsen et al. 2008) may support such a view. No study has yet investigated the association of cannabis and neurocognitive functioning across the diagnostic categories. Both neuropsychological test performance and individual effects of substance use can be regarded as endophenotypes, mediating factors between the neurobiological substrate and the expressed phenotype (Gottesman & Gould, 2003). This can help in assessing whether there is a continuum of traits between the diagnostic groups rather than distinct categories as proposed in the mood-psychosis spectrum continuum model. The relationships between substance use and neurocognitive performance across both disorders can be used to inform the question of dimensions versus categories in the nosology of severe mental illness, and may thus provide new knowledge about underlying disease mechanisms. The present study was conducted on a large, naturalistic and thoroughly described representative patient population, where a range of possible confounders was controlled for. The naturalistic design enables observation of real-life associations in an actual clinical setting. The aim was to investigate if there are differences in neurocognitive functioning between cannabis users and non-users in bipolar disorder and schizophrenia, and if these relationships are different in the two diagnostic groups. Method Setting The study is part of the Thematic Organized Psychosis Research (TOP) study. Patients were recruited from the Departments of Psychiatry at Ulleval University Hospital, Aker University Hospital and Diakonhjemmet Hospital in Oslo. The three departments cover a geographical catchment area including 10 districts of Oslo and five suburbs. The catchment areas covers 485 000 inhabitants (88% of Oslos total population), are located in different areas of the city and are representative of the citys variation in sociodemographic characteristics. Subjects Patients that consecutively gave consent to enter the study between May 2003 and September 2007 were included in the present part of the study. Each patient was referred to the project by their treating clinician after an evaluation of their eligibility and ability to give informed consent. Emphasis was put on recruiting all patients regardless of level of involvement in their respective treatment programmes. All patients had given written informed consent to participation, and the study was approved by the Regional Committee for Medical Research Ethics and the Norwegian Data Inspectorate. In the main TOP study the rate of non-participants was about 13%. Due to the Norwegian Data Security Act, information about non-consenting patients is inaccessible. We have previously shown that the TOP sample is representative of psychosis patients receiving treatment at Oslo University Hospital (Ringen et al. 2007). The assessments were conducted by trained clinicians working as research fellows (psychiatrists or psychologists) before signing the informed consent, and before the interview started. The recruitment teams were based in out-patient clinics, which patients were transferred to after acute illness phases. This procedure restricted inclusion to symptomatically stable patients. Further inclusion criteria were: aged 18-65 years and meeting DSM-IV criteria for a diagnosis of schizophrenia, schizophreniform disorder, schizo-affective disorder, bipolar I disorder, bipolar II disorder or bipolar disorder not otherwise specified (NOS). Subjects had to be fluent in a Scandinavian language. Exclusion criteria were presence of a diagnosis of developmental disorder [intelligence quotient (IQ)
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