Substance Abuse and Dependence Health Article

Causes

The causes of substance dependence are not well-established, but three factors are believed to contribute to substance-related disorders: genetic factors, psychopathology, and social learning. In genetic epidemiological studies of alcoholism, the probability of identical twins both exhibiting alcohol dependence was significantly greater than with fraternal twins, thus suggesting a genetic component in alcoholism. It is unclear, however, whether the genetic factor is related to alcoholism directly, or whether it is linked to other psychiatric disorders that are known to be associated with substance abuse. For example, there is evidence that alcoholic males from families with depressive disorders tend to have more severe courses of substance dependence than alcoholic men from families without such family histories.

These and other empirical findings that relate psychological pathologies to substance dependence are also consistent with a model of substance dependence where substance use is a way to relieve the symptoms of a psychological disorder. In this model, the psychopathology is the cause of ongoing substance use because individuals use the substance to alleviate their subjective experience of the pathology. Unless the underlying pathology is treated, attempts to permanently stop substance dependence are ineffective. Psychopathologies that are associated with substance dependence include antisocial personality disorder, bipolar disorder, depression, anxiety disorder, and schizophrenia.

A third factor related to substance dependence is social environment. In this model, drug-taking is essentially a socially learned behavior. Local social norms determine the likelihood that a person is exposed to the substance and whether continued use is reinforced. For example, individuals may, by observing family or peer role models, learn that substance use is a normal way to relieve daily stresses. External penalties, such as legal or social sanctions, may reduce the likelihood of substance use.

At the level of neurobiology, it is believed that substances of abuse operate through similar pathways in the brain (one well-known pathway is the "mesolimbic dopamine system" or "mesolimbic reward pathway"). The chemical changes induced by the stimulation of these pathways by initial use of the substance lead to the desire to continue substance use, possibly leading to substance dependence.

Symptoms

The DSM-IV-TR identifies seven criteria (symptoms), at least three of which must be met during a given 12-month period, for the diagnosis of substance dependence:

• Tolerance, as defined either by the need for increasing amounts of the substance to obtain the desired effect or by experiencing less effect with extended use of the same amount of the substance.
• Withdrawal, as exhibited either by experiencing unpleasant mental, physiological, and emotional changes when drug-taking ceases or by using the substance as a way to relieve or prevent withdrawal symptoms.
• Substance is taken for a longer duration or in greater quantities than was originally intended.
• Persistent desire or repeated unsuccessful efforts to stop or attenuate substance use.
• A relatively large amount of time spent in securing and using the substance, or in recovering from the effects of the substance.
• Important work and social activities reduced because of substance use.
• Continued substance use despite negative physical and psychological effects of use.

Although not explicitly listed in the DSM-IV-TR criteria, "craving, " or the overwhelming desire to use the substance regardless of countervailing forces, is a universally-reported symptom of substance dependence.

Symptoms of substance abuse, as specified by DSM-IV-TR, include one or more of the following occurring during a given 12-month period:

• Substance use resulting in a recurrent failure to fulfill work, school, or home obligations (e.g. work absences, substance-related school suspensions, neglect of children).
• Substance use in physically hazardous situations such as driving or operating machinery.
• Substance use resulting in legal problems such as drug-related arrests.
• Continued substance use despite negative social and relationship consequences of use.

In addition to the general symptoms, there are other physical signs and symptoms of substance abuse that are related to specific drug classes:

• Signs and symptoms of alcohol intoxication are well-known; these include such physical signs as slurred speech, lack of coordination, unsteady gait, memory impairment, and stupor, as well as behavior changes manifesting themselves shortly after alcohol ingestion, including inappropriate aggressive behavior, mood volatility, and impaired functioning.
• Amphetamine users may exhibit rapid heartbeat, elevated or depressed blood pressure, dilated (enlarged) pupils, weight loss, as well as excessively high energy, inability to sleep, confusion, and occasional paranoid psychotic behavior.
• Cannibis users may exhibit red eyes with dilated pupils, increased appetite, dry mouth, and rapid pulse; they may also be sluggish and slow to react.
• Cocaine users may exhibit rapid heart rate, elevated or depressed blood pressure, dilated pupils, weight loss, in addition to wide variations in their energy-level, severe mood disturbances, psychosis, and paranoia.
• Users of hallucinogens may exhibit anxiety or depression, paranoia, and unusual behavior in response to hallucinations (imagined sights, voices, sounds, or smells that appear real). Signs include dilated pupils, rapid heart rate, tremors, lack of coordination, and sweating. Flashbacks, or the re-experiencing of a hallucination long after stopping substance use, are also a symptom of hallucinogen use.
• Users of inhalants experience dizziness, spastic eye movements, lack of coordination, slurred speech, and slowed reflexes. Associated behaviors may include belligerence, predisposition to violence, apathy, and impaired judgment.
• Opioid drug users exhibit slurred speech, drowsiness, impaired memory, and constricted (small) pupils. They may appear slowed in their physical movements.
• Phencyclidine users exhibit spastic eye movements, rapid heartbeat, decreased sensitivity to pain, and lack of muscular coordination. They may show belligerence, predisposition to violence, impulsiveness, and agitation.
• Users of sedative, hypnotic, or anxiolytic drugs show slurred speech, unsteady gait, inattentiveness, and impaired memory. They may display inappropriate behavior, mood volatility, and impaired functioning.

Other signs are related to the form in which the substance is used. For example, heroin, certain other opioid drugs, and certain forms of cocaine may be injected. A person using an injectable substance may have "track marks" (outwardly visible signs of the site of an injection, with possible redness and swelling of the vein in which the substance was injected). Furthermore, poor judgment brought on by substance use can result in the injections being made under dangerously unhygienic conditions. These unsanitary conditions and the use of shared needles are risk factors for major infections of the heart, as well as infection with HIV (the virus that causes AIDS), certain forms of hepatitis (a liver infection), and tuberculosis.

Cocaine is often taken as a powdery substance which is "snorted" through the nose. This can result in frequent nosebleeds, sores in the nose, and even erosion (an eating away) of the nasal septum (the structure that separates the two nostrils).

Overdosing on a substance is a frequent complication of substance abuse. Drug overdose can be purposeful (with suicide as a goal), or due to carelessness, the unpredictable strength of substances purchased from street dealers, mixing of more than one type of substance, or as a result of the increasing doses that a person must take to experience intoxicating effects. Substance overdose can be a life-threatening emergency, with the specific symptoms depending on the type of substance used. Substances with depressive effects may dangerously slow the breathing and heart rate, drop the body temperature, and result in a general unresponsiveness. Substances with stimulatory effects may dangerously increase the heart rate and blood pressure, produce abnormal heart rhythms, increase body temperature, induce seizures, and cause erratic behavior.