What are substance use disorders?

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Substance use disorders include the formal medical diagnoses of substance abuse and substance dependence for many types of drugs of abuse, including alcohol and prescription drugs. These disorders are characterized by recurrent problems in everyday life and physical or emotional distress and impairment that are caused or exacerbated by the use of the substances of abuse.
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Substance use is studied in psychology from personality, social, and biological perspectives. Social and personality studies of individuals with substance use disorders have produced a variety of theories. These theories have focused on issues such as difficulties people might have with tolerating stress, being unable to delay gratification, developing social skills, being socially isolated or marginalized, being attracted to taking risks, and having difficulties regulating their own behavior. Additionally, environmental issues, such as poverty or high levels of stress, have been linked to substance use problems. Biological theories of these disorders suggest that genetic and conditioned sensitivities to substances of abuse and their effects may predispose individuals to acquire these disorders. For instance, people who have increased needs to seek relief from pain or have an increased need to seek pleasure or euphoria might be at greater risk for developing such problems. Pain is broadly defined as any feeling of dysphoria. Because both pain and euphoria can be produced by psychosomatic or somatopsychic events, these two biological categories can subsume most of the stated nonbiological correlates of substance abuse.

There are several forms of substance use disorders, including abuse and dependence. These should be contrasted with normal experimentation, normal use without problems, and limited instances of misuse that are more appropriately attributed to situational factors than an underlying psychiatric disorder.

There are several types of substances of abuse, and some of these are not typically viewed as problematic. Major categories include sedatives/hypnotics; alcohol; nicotine; marijuana; opioids, such as heroin; stimulants, including amphetamine, cocaine, crack, and caffeine; inhalants, such as glue, paint, nitrous oxide (laughing gas), and shoe polish; hallucinogens, including phencyclidine (PCP or “angel dust”), lysergic acid diethylamide (LSD, or “acid”), and MDMA (an amphetamine-like drug with hallucinogenic effects, also known as X or ecstasy); anabolic steroids; and some types of prescription drugs, such as diazepam (Valium) or oxycodone (Oxycontin).

When diagnoses are given for substance use disorders, diagnoses should be given in terms of a specific type of substance. A diagnosis of “substance abuse” would be too general, because it does not specify the substance causing the problem. Having problems with one substance does not automatically mean that a person has problems with all substances. Thus, any diagnosis for a substance use disorder should be substance specific; examples might include alcohol abuse, inhalant abuse, marijuana abuse, cocaine dependence, or stimulant abuse.

For the substance abuse category, the key features of the disorder are patterns of repeated problems in individual functioning in terms of roles at work, school, or home; legal status; use of the substance in hazardous situations; or the consequences of the use on interpersonal relationships. For the substance dependence category, the key features of the disorder are patterns of repeated problems in several areas that are distinct from those considered for abuse. Diagnosis of dependence relies on factors such as tolerance; withdrawal; new or worsened physical or emotional problems directly resulting from the use of the substance; loss of control over the use of the substance; unsuccessful efforts to cut down or quit coupled with intense desire to quit; excessive periods of time spent obtaining, using, or recovering from using the substance; and the displacement of social or occupational activities to use the substance.

Pain and Euphoria

The experience of pain or the seeking of euphoria as causes of substance use disorders can be measured physically or can be perceived by the individual without obvious physical indicators. The relative importance of pain and euphoria in determining the development and maintenance of substance use disorders requires consideration of the contributions of at least five potential sources of behavioral and physical status: genetic predisposition, dysregulation during development, and dysregulation from trauma at any time during the life span, the environment, and learning. Any of these can result in or interact to produce the pain or feelings of euphoria that can lead to substance use disorders.

The key commonality in pain-induced substance use disorders is that the organism experiences pain that it does not tolerate. Genetic predisposers of pain include inherited diseases and conditions that interfere with normal pain tolerance. Developmental dysregulations include physical and behavioral arrests and related differences from developmental norms. Trauma from physical injury or from environmental conditions can also result in the experience of pain, as can the learning of a pain-producing response.

Several theories of pain-induced substance use disorders can be summarized as self-medication theories. In essence, these state that individuals misuse substances to correct an underlying disorder that presumably produces some form of physical or emotional distress or discomfort. Self-medication theories are useful because they take into account the homeostatic (tendency toward balance) nature of the organism and because they include the potential for significant individual differences in problems with pain.

Relief from pain by itself does not account entirely for drug use that goes beyond improvement in health or reachievement of normal status and certainly cannot account entirely for drug use that becomes physically self-destructive. Thus, the use of substances to achieve positive effects such as euphoria or pleasure is also important to consider as a cause of these disorders. Associative conditioning and operant conditioning effects play an important role as well. This type of substance misuse can be distinguished from the relief caused by substance use to decrease pain because the substance use does not stop when such relief is achieved, but continues until the person experiences the pleasurable effects.

Euphoria-induced substance use, or pleasure seeking, is characteristic of virtually all species tested. Some theorists have proposed that pleasure seeking is an innate drive not easily kept in check even by socially acceptable substitutes. Other theorists believe that these types of substance use disorders related to the positively reinforcing aspects of the substances may have developed as a function of biological causes such as evolutionary pressure and selection. For example, organisms that could eat rotten, fermented fruit (composed partly of alcohol) may have survived to reproduce when others did not; people who could tolerate or preferred drinking alcohol instead of contaminated water reproduced when those who drank contaminated water did not.

Substance Use Disorder Research

Laboratory studies of the biological bases of substance abuse and dependence involve clinical (human) and preclinical (animal) approaches. Such research has demonstrated that there are areas of the brain that can provide powerful feelings of euphoria when stimulated, indicating that the brain is primed for the experience of pleasure. Direct electrical stimulation of some areas of the brain, including an area first referred to as the medial forebrain bundle, produced such strong addictive behaviors in animals that they ignored many basic drives including those for food, water, mating, and care of offspring.

Later research showed that the brain also contains highly addictive analgesic and euphoriant chemicals that exist as a normal part of the neural milieu. Thus, the brain is also predisposed to aid in providing relief from pain and has coupled such relief in some cases with feelings of euphoria. It is not surprising, therefore, that substance abuse, dependence, and other behaviors with addictive characteristics can develop so readily in so many organisms.

The effects of typical representatives of the major categories of abused substances can be predicted. Alcohol can disrupt several behavioral functions. It can slow reaction time, movement, and thought processes and can interfere with needed rapid eye movement (REM) sleep. It can also produce unpredictable emotionality, including violence. Those who abuse alcohol may go on to develop the symptoms of physiological dependence (a condition in which tolerance or withdrawal are present) and may go on to develop the full diagnosis of alcohol dependence, and it is important to note that the symptoms of alcohol withdrawal can be life-threatening. Heroin, an opioid, has analgesic (pain-killing) and euphoriant effects. It is also highly addictive, but withdrawal seldom results in death. Marijuana, sometimes classified as a sedative and sometimes as a hallucinogen, has many of the same behavioral effects as alcohol.

Stimulants vary widely in their behavioral effects. Common to all is some form of physiological and behavioral stimulation. Some, such as cocaine and the amphetamines (including methamphetamine), are extremely addictive and seriously life-threatening and can produce violence. Others, such as caffeine, are relatively mild in their euphoriant effects. Withdrawal from stimulants, especially the powerful forms, can result in profound depression.

Hallucinogens are also a diverse group of substances that can produce visual, auditory, tactile, olfactory, or gustatory hallucinations, but most do so in only a small percentage of the population. Some, such as PCP, can produce violent behavior, while others, such as LSD, are not known for producing negative emotional outbursts. Inhalants usually produce feelings of euphoria; they are most often used by individuals in their adolescent years who cannot afford to buy other types of drugs such as marijuana, as well as by adult individuals who have easy access to these substances in their work environments or social circles.

Brain Chemistry

It is noteworthy that some of the pharmacological effects of very different drugs are quite similar. Marijuana and alcohol affect at least three of the same brain biochemical systems. Alcohol can become a form of opiate in the brain following some specific chemical transformations. These similarities raise an old and continuing question in the substance use field: Is there a fundamental addictive mechanism common to everyone that differs only in the level and nature of expression? Older theories of drug-abuse behavior approached this question by postulating the addictive personality, a type of person who would become indiscriminately addicted as a result of his or her personal and social history. With advances in neuroscience have come theories concerning the possibility of an addictive brain, which refers to a neurological status that requires continued adjustment provided by drugs.

An example of the workings of the addictive brain might be a low-opiate brain that does not produce normal levels of analgesia or normal levels of organismic and behavioral euphoria (joy). The chemical adjustment sought by the brain might be satisfied by use or abuse of any drug that results in stimulation of the opiate function of the brain. As discussed above, several seemingly unrelated drugs can produce a similar chemical effect. Thus, the choice of a particular substance might depend both on brain status and on personal or social experience with the effects and availability of the drug used.

The example of the opiate-seeking brain raises at least two possibilities for prevention and treatment, both of which have been discussed in substance use literature: reregulation of the brain and substitution. So far, socially acceptable substitutes or substitute addictions offer some promise, but reregulation of the dysregulated brain is still primarily a hope of the future. An example of a socially acceptable substitute might be opiate production by excessive running, an activity that can produce some increase in opiate function. The success of such a substitution procedure, however, depends on many variables that may be quite difficult to predict or control. The substitution might not produce the required amount of reregulation, the adjustment might not be permanent, and tolerance to the adjustment might develop. There are a host of other possible problems.

Future Possibilities

Use of psychoactive substances dates from the earliest recorded history and most likely predates it. Historical records indicate that many substances with the potential for abuse were used in medicinal and ceremonial or religious contexts, as tokens in barter, for their euphoriant properties during recreation, as indicators of guilt or innocence, as penalties, and in other practices.

Substance use disorders are widespread in virtually all countries and cultures and can be extremely costly, both personally and socially. There is no doubt that most societies would like to eliminate substance use disorders, as many efforts are under way to prevent and treat their occurrence. It is obvious that economic as well as social factors contribute both to substance use disorders and to the laws regulating substance use and possibly create some roadblocks in eliminating abuse and dependence.

In psychology, the systemic and popular study of substance use became most extensive as the field of pharmacology blossomed and access to substances of abuse increased. The creation of the National Institute of Alcohol Abuse and Alcoholism and the National Institute on Drug Abuse helped to fuel research in this area in the 1970s and later. During the 1980s and 1990s, there was an increase in exploration of the biological mechanisms underlying substance use disorders and the possibility that pharmacological interventions might be useful to prevent and treat substance use disorders. The 1990s also brought an increase in awareness among the research and clinical communities that attention to specific demographic characteristics, such as age, gender, and ethnicity, was also important for understanding the etiology, prevention, and treatment of substance use disorders. As research progresses in the early twenty-first century, these factors and the impact of the environment on behavior are increasingly the focus of study, and attention to the diagnosis of abuse is increasing.

Future research on substance use disorders is likely to focus on biological determinants of the problem for the purposes of prevention and treatment, environmental circumstances related to problem development, the interaction of culture and gender as they relate to substance use disorders and treatments, and how other mental illnesses can compound problems related to substance use. Many people erroneously consider biological explanations of problematic behaviors to be an excuse for such behaviors. In fact, discoveries regarding the neural contributions to such behaviors are the basis on which rational therapies for such behaviors can be developed. Recognizing that a disorder has a basis in the brain can enable therapists to address the disorder with more useful therapeutic tools. In this way, simple management of such disorders can be replaced by real solutions to the problems created by substance abuse.


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