Biological thumb 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<unk> , which indicated that differences in these genes can create the risk of being dependent on multiple substances. Psychological A 1989 study conducted by Khantzian and Treece found that nearly 60% of their opioid-dependent sample met criteria for an Axis II 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<unk>  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<unk> . 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<unk> . 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 it, 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<unk> . :In the older generations,<unk>  had been linked to additional considerations such as personality disorder, homelessness, bipolar disorder, major depressive disorder and so on. Medical care being so expensive and difficult to get long term has been linked to<unk> . Those who need psychological help sometimes use multiple substances as a type of self medication to help manage their mental illnesses.
Polysubstance dependence
Benzodiazepine dependence
Amphetamine dependence
Substance dependence
Nicotine dependence
Cocaine dependence
Addiction
Benzodiazepine use disorder