Hashja schreef:Klopt wat je zegt, hier een quote uit dat artikel:
Findings: We found little evidence of decreased cognitive performance in ecstasy users, save for poorer strategic self-regulation, possibly reflecting increased impulsivity. However, this finding might have reflected a pre-morbid attribute of ecstasy users, rather than a residual neurotoxic effect of the drug.
Toch vond ik dit artikel wel discussie waardig materiaal.
Ik wou ook zeker niet impliceren dat het geen toegevoegde waarde heeft
Ik zit net een beetje te bladeren in "Understanding Drugs and Behaviour" een boek uit 2004. Daarin kwam ik het volgende stukje tegen:
Halpern et al. (2004) described some intriguing findings from a study of young ravers in Salt Lake City, where the prevailing religious beliefs have led to very low rates of tobacco, alcohol, cannabis or other illicit drug consumption. However, many of these ravers did use MDMA and, while moderate users were not cognitively impaired, high users (60–450 lifetime occasions) displayed significant deficits on many of the cognitive test measures, particularly those associated with processing speed, memory and impulsivity (Table 6.1).
These deficits remained even after controlling for a range of potential confounding factors. However, cognition and memory are not the only areas of psychobiological deficit. Regular Ecstasy/MDMA users have been reported to experience sleep impairments, eating disorders, reduced sexual functioning, phobic anxiety, depression, heightened impulsivity, aggressiveness and a range of occu- pational, health and financial problems (McCann et al., 2000; Parrott, 2000; Schifano et al., 1998; Schifano, 2000; Topp et al., 1999)
Many recreational users are fully aware of these problems. In a World Wide Web (WWW) study of 283 unpaid volunteers (Parrott et al., 2002), around 73% of the excessive Ecstasy users stated that they had experienced memory problems that they attributed to the use of Ecstasy, while many other problems were also reported (Table 6.2).
Quote uit het onderzoek dat je linkt:
Life-time episodes of ecstasy use: 43.5
Als ik het goed interpreteer is de median 43.5 episodes van XTC gebruik onder sample van 52 users. Als je dan kijkt naar mijn quote wordt er gesproken van cognitieve deficits bij lifetime gebruik > 60. Dat zou natuurlijk een verklaring kunnen zijn waarom er inderdaad geen significant verschil gevonden word tussen de non-users en users. Aangezien het gebruik rond de 43.5 lifetimes ligt.
Er word ook heel mooi een stukje aangekaart over methodological problemen bij het onderzoek doen naar recreatie drugs gebruik.
The standard approach is to compare drug users with non-users as controls; but, there are many problems with this design. The main one is that groups are self-selected and may differ in important characteristics related to the decision to use illicit drugs. It is often possible to measure or match groups on some of these factors: age, gender and socioeconomic background can all be measured fairly easily; and intellectual ability could be estimated by measures of school attainment or verbal comprehension tasks.
Although, both these measures may be affected by drug use. Similarly, a variety of personality questionnaires might be administered. However, even if the different groups were matched on a range of factors, it could be that they still differed a priori on some important but unassessed attributes.
Another problem is lack of control over drug administration. The standard approach is to ask subjects to recall which drugs they have taken; but, this raises the question of how accurate these estimates might be – particularly with heavy users. There is also the question of drug strength and purity, since illicit drug supplies can sometimes be quite variable (Parrott, 2004).
However, there are several ways in which the influence of these disparate factors could be investigated. For instance, it is often possible to statistically control for the influence of other psychoactive drugs, by multiple regression or partial correlation. Where this has been done the cognitive/memory deficits displayed by Ecstasy users still remain (Verkes et al., 2001).
While current evidence suggests a profile of specific cognitive deficits in regular MDMA users, a number of important questions remain, nevertheless. How much MDMA needs to be taken before problems develop? The answer would seem to be not a lot (Halpern et al., 2004). Is there evidence for neural recovery once drug taking has stopped? Morgan et al. (2002) suggested that psychobiological problems recovered whereas selective memory deficits remained. Another core topic is the contributory role of high tempera- ture. Animal studies have shown that neuronal toxicity is heightened when rats are allowed to become hyperthermic; this raises the question of whether neurotoxicity also develops most in those recreational Ecstasy users who become overheated (McCann et al., 2000; Parrott, 2000, 2002; Ricaurte et al., 2000).
Voor de goede orde de rest van het stukje:
MDMA/Ecstasy and neurotoxicity
One of the main concerns about MDMA is the laboratory animal data demonstrating that it is neurotoxic. In rats and monkeys, brain levels of serotonin are reduced by repeated doses of MDMA, a finding replicated in numerous studies (e.g., Steele et al., 1994), while there is also evidence for dopaminergic nerve damage (Ricaurte et al., 2002).
The main effect is destruction of serotonin nerve axons in the cerebral cortex and other higher brain areas. The cell bodies in the dorsal raphe nucleus of the brainstem are spared, whereas the prolonged axon terminals and distal projections are destroyed, leading to reduced serotonin activity in the higher brain regions. Thus, there is concern over whether higher brain functions, such as information storage and retrieval, complex stimulus analysis and decision taking, might be impaired. Many other brain regions are also affected, including the hypothalamus and suprachiasmatic nucleus, areas that subserve temperature regulation, feeding behaviour and biological rhythms.
The data from laboratory animals administered MDMA raises the possibility that recreational Ecstasy may also be neurotoxic for humans. It is not possible to investigate this hypothesis directly (see below), but there is a great deal of evidence for serotonergic damage in recreational Ecstasy users. Drug-free, regular MDMA users demonstrate reduced serotonin neural activity in the cerebral cortex in PET (positron emission tomography) scans, reduced levels of cerebrospinal 5-HIAA, or hydroxyindoleacetic acid (the main serotonin metabolite) and other indices of reduced serotonin activity (McCann et al., 2000; Reneman et al., 2001).
Regular Ecstasy users display significant deficits in a number of psychobiological functions subserved by serotonin. The most thoroughly studied area is memory, and significant deficits in abstinent Ecstasy users have been found on a wide range of episodic and working memory tasks (Fox et al., 2002; Rodgers et al., 2001; Verkes et al., 2001; see Table 6.1). Deficits have also been found in some measures of cognitive planning and higher executive processing, although many basic cognitive functions remain unimpaired.
Quote uit:
Residual neurocognitive features of long-term ecstasy users with minimal exposure to other drugsFindings We found little evidence of decreased cognitive performance in ecstasy users, save for poorer strategic self-regulation, possibly reflecting increased impulsivity. However, this finding might have reflected a pre-morbid attribute of ecstasy users, rather than a residual neurotoxic effect of the drug.
Toch wel noemenswaardig dat ze in dit onderzoek het toeschrijven aan andere oorzaken. Terwijl in mijn quote het volgende word gesteld voor regular users: "
Deficits have also been found in some measures of cognitive planning and higher executive processing" Waar strategic self-regulation toe behoort als ik het mij correct herinner.
P.S. Petrovic hopelijk ga ik niet te zeer off-topic anders hoor ik het wel. Bestaat er misschien niet een mogelijkheid om de discussie samen te voegen met:
viewtopic.php?f=45&t=461 ?
“Scientists do not speak in absolutes, they present the results that support the hypothesis and the tolerance for error.”
