27 Nov Cocaine and Cannabis Use Leads to Addictive Behavior, Study Finds
A new study published in the British Journal of Pharmacology investigated the effects of cocaine and cannabis on psychomotor functioning and impulse control, providing evidence that the drugs increase impulsivity and could thereby contribute to the development of addiction.
Previous research looked into these effects in cannabis users and led to the conclusion that impairment of cognitive function in pot smokers was limited to specific regions of functioning and is mainly an issue for occasional users, with heavy smokers assumed to develop a tolerance to the drug’s effects. The new research calls these findings into question, showing that even regular cannabis users suffer impairment in both areas of functioning, although the effect is still greater in occasional users. The study raises important questions about the likelihood of further drug experimentation after cocaine or cannabis use, thus providing a plausible explanation for the “gateway” hypothesis.
Cannabis is the most popular illicit drug in the United States and the European Union, and cocaine is ranked a close second in many countries. In addition, many users of cannabis also take cocaine, and there is evidence from animal studies that suggests heavy use of cannabis may confer some tolerance to the effects of cocaine on the user. The main aim of this study was to investigate the supposed difference in the cognitive effects of cannabis in regular users compared to occasional users, but the researchers were also able to look at the potential for cross-tolerance between the substances.
What They Did
The research was fairly simple in terms of methodology. The researchers increased the number of participants (in comparison to previous research) to add some statistical weight to their conclusions, recruiting 61 subjects (48 men, 13 women) who used cannabis at least twice per week and had used cocaine more than five times in the previous year. The participants were all average weight, between the ages of 18 and 28, and did not consume excessive amounts of alcohol or cigarettes.
The test was placebo-controlled and double-blind, meaning that each participant was either given an inactive sugar pill or the drug being tested (cocaine or marijuana), and neither they nor the researchers knew which participants were receiving which treatment. This helps to ensure that the effects observed weren’t related to either the user or the experimenters’ expectations of the effects of a specific drug. Each participant was involved in more than one test, but the testing days were separated by a minimum of seven days to prevent cross-contamination.
On a test day, the participants were first given a pill either containing cocaine or a placebo, before waiting 45 minutes and inhaling vaporized cannabis or an inactive placebo. Immediately after this second dosing, the participants were given a test to indicate how “high” or active they felt, followed by several tests to measure impulsivity and psychomotor (cognitive control of motor functions) performance. For example, the participants’ ability to stop performing a task on cue, the time it took them to react to the instruction and the amount of mistakes made was used as a measure of impulsivity, and other cognitive areas such as forward planning were also tested.
What They Found
For the impulsivity tests, both cocaine and cannabis use impacted the users’ performance. The end result was that participants who’d taken a single dose of either drug made more errors, but they did so for different reasons. Cocaine users responded more quickly, but made more errors than when they’d only taken a placebo and marijuana users responded more slowly but still made more errors than in the placebo condition. These responses were unrelated to the participants’ history of cannabis use, suggesting that heavier smokers were not immune from these effects.
For psychomotor functioning, cannabis was shown to have a detrimental effect whereas cocaine actually improved participants’ performance. This was again shown to be unrelated to the specific participants’ previous use of marijuana. In addition, heavy users of cannabis were still affected by cocaine in both tests, suggesting that the animal studies that uncovered a potential cross-tolerance may have been flawed.
Although the effect of pot was impairment across the board, there was some difference between heavy and occasional users. On some of the tests, occasional users were affected twice to three times more than regular users, suggesting that tolerance does reduce at least some of the impairing effects of marijuana.
What Does It Mean?
The research has many potential implications for our understanding of marijuana and cocaine use. The increase in impulsive behavior could lead to an increased susceptibility to addiction: in other words, if you smoke pot, you’re more likely to make an impulsive and flawed decision to take more drugs and become addicted as a result. This is also true for cocaine, but given the greater relative popularity of pot, it arguably adds some credence to the “gateway” theory of drug use. Pot use—although not shown to cause further drug use—could make you less able to make objective choices and therefore lead you to take other substances. Neurologically speaking, cocaine may increase the knee-jerk impulsive response from the mammalian (limbic) brain and marijuana may decrease the ability of the frontal cortex to exert its intelligent, rational control over behavior.
The research is still somewhat limited, however, in that the results just give an indication of what may be happening in the brain. For a confirmation of the theory resulting from this study, further studies (using neuro-imaging technology) will be required. Some important conclusions can be inferred from this research directly, however: that previous cannabis use does confer some resistance to the cognitive impairment it causes but doesn’t prevent it, and that regular cannabis users will not be inherently tolerant to cocaine. Both drugs have the potential to lead users down the road to addiction, and the impact on day-to-day problem solving and impulse control could have numerous additional consequences for users.
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