Reduced memory and attention performance in a population-based sample of young adults with a moderate lifetime use of cannabis, ecstasy and alcohol

Abstract

Regular use of illegal drugs is suspected to cause cognitive impairments. Two substances have received heightened attention: 3,4-methylenedioxymethamphetamine (MDMA or 'ecstasy') and delta-9-tetrahydrocannabinol (THC or 'cannabis'). Preclinical evidence, as well as human studies examining regular ecstasy consumers, indicated that ecstasy use may have negative effects on learning, verbal memory and complex attentional functions. Cannabis has also been linked to symptoms of inattention and deficits in learning and memory. Most of the published studies in this field of research recruited participants by means of newspaper advertisements or by using word-of-mouth strategies. Because participants were usually aware that their drug use was critical to the research design, this awareness may have caused selection bias or created expectation effects. Focussing on attention and memory, this study aimed to assess cognitive functioning in a community-based representative sample that was derived from a large-scale epidemiological study. Available data concerning drug use history allowed sampling of subjects with varying degrees of lifetime drug experiences. Cognitive functioning was examined in 284 young participants, between 22 and 34 years. In general, their lifetime drug experience was moderate. Participants completed a neuropsychological test battery, including measures for verbal learning, memory and various attentional functions. Linear regression analysis was performed to investigate the relationship between cognitive functioning and lifetime experience of drug use. Ecstasy and cannabis use were significantly related to poorer episodic memory function in a dose-related manner. For attentional measures, decrements of small effect sizes were found. Error measures in tonic and phasic alertness tasks, selective attention task and vigilance showed small but significant effects, suggesting a stronger tendency to experience lapses of attention. No indication for differences in reaction time was found. The results are consistent with decrements of memory and attentional performance described in previous studies. These effects are relatively small; however, it must be kept in mind that this study focussed on assessing young adults with moderate drug use from a population-based study.

Effects of ecstasy/polydrug use on memory for associative information

“…For example, in an ERP study, Croft et al (2001a) found that lifetime dose of ecstasy was associated with 5-HT dysfunction after partially out the effects of variations in the current frequency of use while there was no association between the frequency of use and 5-HT when the effects of differences in lifetime does were controlled. Similarly other studies examining different aspects of cognition have found a significant lifetime dose related effect in relation to ecstasy (e.g., Indlekofer et al 2009;Schilt et al 2008). Nonetheless, in the present study, it appears that ecstasy related impairment in associative learning is associated with more refined and explicit measures of ecstasy use.…”

Os impactos na capacidade atencional em trabalhadores usuários de drogas

“…A alteração da atenção em usuários de drogas também foi observada no estudo de Indlekofer et al 21 , sugerindo uma forte tendência a lapsos de atenção; porém não observou diferenças na média do tempo de reação quando comparados ao grupo controle, o que difere dos presentes achados.…”

Reasoning deficits among illicit drug users are associated with aspects of cannabis use

“…In a few instances, responses were missing from the questionnaire possibly due to questions being overlooked. A degree of missing data is not uncommon in studies of this kind (e.g., Bedi & Redman, 2008;Indlekofer et al 2009). However, while we wished to avail ourselves of the largest possible sample for each of the comparisons in question, it should be borne in mind that some of the significant associations (or lack of them) reported in Table 2 relate to subsets of the data.…”