Etiology - Substance Abuse

ETIOLOGY

The exact causes of drug use, dependence, and addiction are not known, but various factors are thought to contrib-ute to the development of substance-related disorders (Jaffe & Anthony, 2005). Much of the research on biologic and genetic factors has been done on alcohol abuse, but psychologic, social, and environmental studies have exam-ined other drugs as well.

Biologic Factors

Children of alcoholic parents are at higher risk for devel-oping alcoholism and drug dependence than are children of nonalcoholic parents. This increased risk is partly the result of environmental factors, but evidence points to the importance of genetic factors as well. Several studies of twins have shown a higher rate of concordance (when one twin has it, the other twin gets it) among identical than fraternal twins. Adoption studies have shown higher rates of alcoholism in sons of biologic fathers with alcoholism than in those of nonalcoholic biologic fathers. These stud-ies led theorists to describe the genetic component of alco-holism as a genetic vulnerability that is then influenced by various social and environmental factors (Jaffe & Anthony, 2005). Schuckit (2009) found that about 50% of the varia-tion in causes of alcoholism was the result of genetics, with the remainder caused by environmental influences.

Neurochemical influences on substance use patterns have been studied primarily in animal research (Jaffe & Anthony, 2005). The ingestion of mood-altering sub-stances stimulates dopamine pathways in the limbic sys-tem, which produces pleasant feelings or a “high” that is a reinforcing, or positive, experience. Distribution of the substance throughout the brain alters the balance of neu-rotransmitters that modulate pleasure, pain, and reward responses. Researchers have proposed that some people have an internal alarm that limits the amount of alcohol consumed to one or two drinks, so that they feel a pleasant sensation but go no further. People without this internal signaling mechanism experience the high initially but con-tinue to drink until central nervous system depression is marked and they are intoxicated.

Psychologic Factors

In addition to the genetic links to alcoholism, family dynamics are thought to play a part. Children of alcoholics are four times as likely to develop alcoholism (Schuckit, 2005) compared with the general population. Some theo-rists believe that inconsistency in the parent’s behavior, poor role modeling, and lack of nurturing pave the way for the child to adopt a similar style of maladaptive coping, stormy relationships, and substance abuse. Others hypoth-esize that even children who abhorred their family lives are likely to abuse substances as adults because they lack adaptive coping skills and cannot form successful relation-ships (NIAAA, 2007a).

Some people use alcohol as a coping mechanism or to relieve stress and tension, increase feelings of power, and decrease psychologic pain. High doses of alcohol, how-ever, actually increase muscle tension and nervousness (Schuckit, 2005).

Social and Environmental Factors

Cultural factors, social attitudes, peer behaviors, laws, cost, and availability all influence initial and continued use of substances (Jaffe & Anthony, 2005). In general, younger experimenters use substances that carry less social disapproval such as alcohol and cannabis, whereas older people use drugs such as cocaine and opioids that are more costly and rate higher disapproval. Alcohol con-sumption increases in areas where availability increases and decreases in areas where costs of alcohol are higher because of increased taxation. Many people view the social use of cannabis, although illegal, as not very harmful; some even advocate legalizing the use of marijuana for social purposes. Urban areas where cocaine and opioids are readily available also have high crime rates, high unem-ployment, and substandard school systems that contribute to high rates of cocaine and opioid use and low rates of recovery. Thus, environment and social customs can influ-ence a person’s use of substances.