Depression
Scientists have hypothesized that the use of a substance either causes a mood disorder such as depression or at least attributes to a pre-existing one. Additionally, the substances that people with depression use can be a misguided method of self-medication in order to manage their depression. This is the classic chicken or egg hypothesis, does the pre-existing condition cause dependence or does dependence cause the condition? The underlying mental illness needs to be identified and treated in conjunction with treating the polysubstance dependence in order to increase the success rate of treatment and decrease the probability of relapse. One specific study focused on alcohol and depression, because they are so commonly inter-related. Researchers have discovered that depression continues for several weeks after a patient had been rehabilitated and those who relapsed developed depression again. This means that the onset of depression happens after alcohol dependence occurs, which means that alcohol is a major contributor to depression. Eating disorders
One study showed that patients who are recovering from an addiction, who have had an eating disorder in the past, often use food to try to replace the substance that they are no longer getting. Or they obsess over controlling their weight and appearance. Some rehabilitation centers have licensed nutritionists to help patients develop healthy eating habits to help them cope while recovering from their addictions. It is important that those who have a former eating disorder be taught how to eat healthfully, so they dont continuously switch from one addiction back to another.
A study involving 63 polysubstance dependent women and 46 controls (participants who were not using substances) used the Benton Visual Retention Test (BVRT) and the California Verbal Learning Test (CVLT) 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.