Polysubstance dependence
Polysubstance dependence refers to a type of substance use disorder in which an individual uses at least three different classes of substances indiscriminately and does not have a favorite substance that qualifies for dependence on its own. Although any combination of three substances can be used, studies have shown that alcohol is commonly used with another substance. One study on polysubstance use categorized participants who used multiple substances according to their substance of preference. The results of a longitudinal study on substance use led the researchers to observe that excessively using or relying on one substance increased the probability of excessively using or relying on another substance.
Common combinations
The three substances were cocaine, alcohol, and heroin, which implies that those three are very popular. Other studies have found that opiates, cannabis, amphetamines, hallucinogens, inhalants, and benzodiazepines are often used in combination as well.Presentation
Associated cognitive impairments
Cognition refers to what happens in the mind, such as mental functions like "perception, attention, memory, language, problem solving, reasoning, and decision making." Although many studies have looked at the cognitive impairments of individuals who are dependent on one substance, there are few researchers who have tried to determine the problems with cognitive functioning that are caused by dependence on multiple substances. Therefore, what is known about the effects of polysubstance dependence on mental abilities is based on the results of a few studies.Learning ability
The effect of polysubstance dependence on learning ability is one area of interest to researchers. A study involving 63 polysubstance dependent women and 46 controls used the Benton Visual Retention Test and the California Verbal Learning Test to look at visual memory and verbal ability. This study showed that in polysubstance dependent women, verbal learning ability was significantly decreased, though visual memory was not affected. In addition, alcohol and cocaine use led to more severe issues with verbal learning, recall, and recognition.Memory, reasoning and decision making
Sometimes studies about specific groups in the general population can be informative. One study decided to test the cognitive abilities of participants in rave parties who used multiple substances. To do this, they compared 25 rave party attenders with 27 control participants who were not using substances. The results of this study indicated that in general, the rave attender group did not perform as well on tasks that tested speed of information processing, working memory, knowledge of similarities between words, ability to attend to a task with interference in the background, and decision making. Certain substances were associated with particular mental functions, but the researchers suggested that the impairments for working memory and reasoning were caused by the misuse of multiple substances.Another study that tried to find differences between the effects of particular substances focused on people with polysubstance use who were seeking treatment for addictions to cannabis, cocaine, and heroin. They studied a group of people with polysubstance use and a group that was not dependent on any substances. Because alcohol was a common co-substance for nearly all of the people in the polysubstance use group, it was difficult to tell exactly which substances were affecting certain cognitive functions. The researchers found that the difference in the two groups' performance levels on executive function, or higher-level cognitive processing tasks were consistently showing that the polysubstance group scored lower than the control group. In general, this meant that multiple substances negatively affected the polysubstance group's cognitive functioning. More specifically, the researchers found that the amount of cannabis and cocaine affected the verbal part of working memory, the reasoning task, and decision making, while cocaine and heroin had a similar negative effect on visual and spatial tasks, but cannabis particularly affected visual and spatial working memory. These results suggest that the combined use of cannabis, cocaine, and heroin impair more cognitive functions more severely than if used separately.
Alcohol's negative effects on learning, spatial abilities and memory has been shown in many studies. This raises a question: does using alcohol in combination with other substances impair cognitive functioning even more? One study decided to try to determine if people with polysubstance use who also recreationally use alcohol would display poorer performance on a verbal learning and memory test in comparison to those who consumed excessive amounts of alcohol specifically. The California Verbal Learning Test was used due to its ability to "quantify small changes in verbal learning and memory" by evaluating errors made during the test and the strategies used to make those errors. The results of this study showed that the group of people with polysubstance and alcohol use performed poorly on the CVLT recall and recognition tests compared to the group of people who exclusively consumed excessive alcohol only, which implies that polysubstance use impaired the memory and learning in a different way than the effects of alcohol alone can explain.
Length of abstinence matter
To examine whether abstinence for long periods of time helps people with polysubstance use recover their cognitive function, a group of researchers tested 207 polysubstance dependent men, of whom 73.4% were dependent on three or more substances. The researchers were interested in six areas of cognitive functioning, which included visual memory, verbal memory, knowledge of words, abstract reasoning, inhibition, and attention. The study used the Benton Visual Retention Test for testing visual memory, the California Verbal Learning Test for verbal memory, the Wechsler Adult Intelligence Scale vocabulary portion for knowledge of words, the Booklet Category Test for abstract reasoning, the Stroop Neuropsychological Screening task for inhibition, and the Trail Making Test for attention. The results showed that neuropsychological ability did not improve with increases in the length of time abstinent. This suggests that polysubstance dependence leads to serious impairment which cannot be recovered much over the span of a year.Causes
Biological
There is data to support that some genes contribute to substance dependence. Some studies have focused on finding genes that predispose the person to be dependent on marijuana, cocaine, or heroin by studying genes that control a person's dopamine and opioid receptors, but no conclusive findings were reported. Other researchers found a connection between dopamine receptor genes and dependency on a substance. A potential problem with this study was that alcohol is commonly used with another substance, so the results of the study may not have been caused by dependency on a single substance. This means that multiple substances may have been contributing to the results, but the researchers suggested that further research should be done.However, there are studies that have found evidence of the influence of genes on vulnerability to substance dependence. These studies often use genotype, or the genetic information found on a person's chromosomes, and phenotype, which consists of the visible features of a person, to look at genetic patterns. One study examined the phenotype and genotype of 1,858 participants from 893 families to look at differences in three nicotinic acetylcholine receptor genes found within these individuals. The experimenters found significant connections between receptor genes for nicotine and polysubstance dependence, which indicated that differences in these genes can create the risk of being dependent on multiple substances.
Psychological
A 1985 study conducted by Khantzian and Treece found that 65% of their opioid-dependent sample met criteria for a personality disorder diagnosis. In the same study, 93% of the sample had a comorbid disorder, implying that the comorbid disorder plays some role in the addiction. It has also been shown that depression and polysubstance dependence are often both present at the same time. If a person is genetically predisposed to be depressed then they are at a higher risk of having polysubstance dependence.Possibly the most widely accepted cause of addictions is the self-medication hypothesis, that views substance addiction as a form of coping with stress through negative reinforcement, by temporarily alleviating awareness of or concerns over the stressor. People who use substances learn that the effects of each type of substance works to relieve or better painful states. They use substances as a form of self-medication to deal with difficulties of self-esteem, relationships, and self-care. Individuals with substance use disorders often are overwhelmed with emotions and painful situations and turn to substances as a coping method.
Sociocultural
The sociocultural causes are areas in a person's life that might have influenced their decision to start and continue using multiple substances. Sociocultural causes can be divided into social causes and cultural causes.- Social Causes: Some studies have shown that adolescents have one of the highest rates of polysubstance dependence. According to one study this population, ages 12–25, represents about half of the nation's population that uses illicit substances. Of these individuals, half of them have started using substances by the end of 12th grade. This could be attributed to social expectations of peers, peer pressure to fit in, or a way of numbing their emotions. Some of these young kids start trying different substances initially to fit in, but then after a while they start to develop a tolerance for these substances and experience withdrawal if they don't have enough substances in their system and eventually become dependent on having the effects of substance dependence. With tolerance comes the craving for additional substances to get high, this constant need for that feeling is polysubstance dependence.