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If we look at the data of recent years, probation admissions to AMATEM Istanbul, which are mostly related to cannabis use, have increased significantly; the number of first admissions/number of control admissions for 2008, 2009 and 2010 are 2318/24261, 3759/31862 and 5639/30959, respectively. As for other psychoactive substances, the negative effects of cannabis use on cognitive functions are well known. Some cannabis-related cognitive function deficits improve after cessation of cannabis use, but growing evidence also suggests that other deficits persist after cannabis is discontinued and may hinder an individual's ability to make the best use of behavioral therapies, putting him or her at greater risk for relapse of cannabis use (1).
Cannabis seems to continue to exert impairing effects in executive functions even after 3 weeks of abstinence and beyond. Although basic attentional and working memory abilities are largely restored, most enduring and detectable deficits are seen in decision-making, concept formation, and planning. Those subjects reporting chronic, heavy cannabis use show the most enduring deficits (2). One can suggest that some of these impairments are not completely reversible upon cessation of cannabis use and moreover may interfere with the treatment of cannabis addiction. Therefore, targeting cognitive impairment associated with chronic cannabis use may be a promising novel strategy for the treatment of cannabis addiction (3).
While acute administration of cannabis to patients with schizophrenia exacerbates symptoms and cognitive impairments and may have enduring effects, cannabis has also been found to have some beneficial effects on cognition, at least in certain subgroups of patients (4). Cannabis using patients had better attention and executive functions than non-cannabis using patients at baseline and after one year of treatment in a representative sample of first-episode schizophrenia patients. Cannabis using patients appear to comprise a subgroup of patients with better premorbid adjustment and premorbid frontal cognitive functions (5).
Thus, while cannabis use is traditionally associated with cognitive impairment, the relationship is more complex in the case of schizophrenia.
References:
1. Blume AW, Marlatt GA. The role of executive cognitive functions in changing substance use: what we know and what we need to know. Ann Behav Med 2009; 37:117-25.
2. Crean RD, Tapert SF, Minassian A, Macdonald K, Crane NA, Mason BJ. Effects of chronic, heavy cannabis use on executive functions. J Addict Med 2011; 5:9-15.
3. Sofuoglu M, Sugarman DE, Carroll KM. Cognitive function as an emerging treatment target for marijuana addiction. Exp Clin Psychopharmacol 2010; 18:109-19.
4. Yücel M, Bora E, Lubman DI, Solowij N, Brewer WJ, Cotton SM, Conus P, Takagi MJ, Fornito A, Wood SJ, McGorry PD, Pantelis C. The impact of cannabis use on cognitive functioning in patients with schizophrenia: a meta-analysis of existing findings and new data in a first-episode sample. Schizophr Bull 2010 (In press)
5. Rodríguez-Sánchez JM, Ayesa-Arriola R, Mata I, Moreno-Calle T, Perez-Iglesias R, González-Blanch C, Periañez JA, Vazquez-Barquero JL, Crespo-Facorro B. Cannabis use and cognitive functioning in first-episode schizophrenia patients. Schizophr Res 2010;124:142-51.