There are a number of syndromes and disorders associated with the general concept of substance abuse. Some of the most common are:
- Intoxication. A reversible, substance-specific physiological and behavioral changes due to recent exposure to a psychoactive substance.
- Addiction. A compulsion to use a drug, usually for its psychic, rather than therapeutic, effects.
- Tolerance. The decline in potency of a drug experienced with continued use, so that higher doses are needed to achieve the same effect. This is a receptor-mediated effect, typical of many psychoactive drugs.
- Physical Dependence. The development of withdrawal symptoms once a drug is stopped.
- Withdrawal. A physiological state that follows cessation or reduction in the amount of a drug used. Generally, these effects are the opposite of the drug’s normal effects.
- Substance Dependence. In the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), this is “a maladaptive pattern of substance use with adverse clinical consequences.”
- Substance Abuse. According to DSM-IV, this is “a maladaptive pattern of use that causes clinically significant impairment.” Symptoms of substance abuse have not met the criteria for substance dependence and do not include tolerance and withdrawal (which can, but do not have to be, features of substance dependence).
- Alcohol intoxication. This refers to the physiological and behavioral response to alcohol use that includes disinhibition, emotional lability, impaired coordination, slurred speech, ataxia, coma, and/or blackouts.
- Alcohol withdrawal. This is the physiological state that results following cessation of alcohol use; it may be uncomplicated (causing tremulousness, anxiety, and/or increased heart rate) or cause potentially serious complications such as seizures and/or delirium tremens (all of which are discussed further below).
- Alcoholism. Though not in DSM-IV (where the term “alcohol dependence” would be used) is remains commonly used by medical clinicians and substance abuse experts. It can be defined as a repetitive, but inconsistent and sometimes unpredictable loss of control of drinking which produces symptoms of serious dysfunction or disability.
Use of psychoactive substances is common in society, and is often socially acceptable, or at least tolerated. Historically, psychoactive substances have served a variety of purposes, including medicinal, social, recreational and religious. In the US, 90% of people report some alcohol use, 80% report some caffeine use, 25% report use of tobacco products, and 37% report having used illicit substances (at least once in their lives). Dependence and Abuse are also very common (13.6% in ECA).
Over 10 million Americans are alcoholics; over 8 million are "problem drinkers." Only 3% of alcoholics are on skid row. Alcoholism is reportedly more common in rural areas and in the undereducated. It is more common in males than females, and more common in adults than teens/kids. However, teenage alcoholism studies show that 15% of high school students are reported to have 5 or more drinks per occasion at least once a week, and 31% of high school students were intoxicated 6 or more times in the past year.
Social/economic factors are considerable in that people in low socioeconomic status are less likely to drink, but more likely to misuse if they do. Drinking is associated with unstable work and family circumstances. Additionally, one should not forget the effect of substance abuse on families. Forty three percent of US adults report exposure to alcoholism in their families. Divorced or separated adults are 3 times as likely as married persons to report having been married to an alcoholic or problem drinker. Additionally, the cost to society is of great importance; alcohol-related deaths are the third leading cause of death in the US, after cancer and heart disease. There are 98,000 alcohol-related deaths per year. Furthermore, it is estimated that the medical complications and associated disability from alcohol abuse costs society $86 billion (along with $58 billion in costs from other substances). Alcoholism is also a major cause of other medical illnesses and injuries. Alcohol may be involved in 20-50% of hospital admissions, though these often go unrecognized. It contributes to 18-20% of ER visits, causes 80% of liver cirrhosis, and 33% of suicides are alcohol-related.
Cultural differences are also apparent in that alcoholism rates vary in different countries. Countries with high rates include Russia, France, Scandinavia, Ireland, and Korea. Those with low rates include China, Islamic countries, and Mediterranean countries
The lifetime prevalence of abuse for substances other than alcohol is as follows:
- Amphetamines: 2%
- Cannabis: 4%
- Cocaine 0.2% (1981 data, probably higher now)
- Hallucinogens: 0.3%
- Opioids: 0.7%
- Sedative hypnotics: 1.1%
The reward pathway and addictionEdit
There is considerable research interest in the notion of a common “reward pathway” in the human brain that may be responsible for the pleasurable feelings experienced by humans in response to both natural stimuli (i.e. food, water, sex) and artificial (i.e. drugs). The major structures of this postulated reward pathway include the ventral tegmental area (VTA), the nucleus accumbens, and the prefrontal cortex. The VTA consists of dopamine-containing neurons that project to both the nucleus accumbens and prefrontal cortex. Thus, it is believed that dopamine has a considerable role in addiction, and indeed, a number of illicit drugs cause increased release of dopamine at these synapses. The most recent research indicates that the reward pathway may be important in both obtaining a reward, and in the associated craving. Opioids, cocaine, and nicotine have been shown to potentiate dopamine release in the reward pathway, and alcohol has been shown activate this pathway indirectly through potentiation of neural activity in the globus pallidus (which in turn connects to components of the reward pathway).
Patterns of cigarette smoking provide an interesting perspective on addiction. It is believed that smokers work, consciously or unconsciously, to maintain blood nicotine levels within the “therapeutic window” by a process referred to as nicotine regulation. For example, the smoker can manipulate the dose of nicotine on a puff-by-puff basis (“finger tip control”). Evidence for this comes from studies of low tar, low nicotine cigarettes. Research has convincingly demonstrated that smokers will compensate for low nicotine yields by smoking more effectively—blocking filter holes to prevent ventilation of smoke; smoking more of the cigarette; inhaling more rapidly and deeply; and smoking a larger total number of cigarettes.
The route of delivery also has implications for addictive potential. For example, with cocaine use, smoking the drug causes an increased rate of its delivery to the brain compared to snorting; hence the greater addictive potential of freebase and crack in patients with cocaine dependence. For nicotine, compared to other forms of its administration, cigarettes offer the most efficient delivery and the fastest spike in blood nicotine levels. Likewise, the subjective effects of smoking a cigarette are greater than the subjective effects after nicotine exposure to the nicotine gum or transdermal patch (types of nicotine replacement therapy to be discussed later).
Alcoholism and geneticsEdit
While 51% of cases of alcoholism are non-familial, genetics has been well established in alcoholism, particularly among young male alcoholics. Any drinking carries with it a 5-10% risk of becoming alcoholic. For children of alcoholics, having one parent with alcoholism is associated with a 20% risk of alcoholism in the child. With two parents, the risk is 20-50%. Sons of father are at greater risk, at 50%. If the father is a severe alcoholic and criminal, there is a 90% risk in his son. Children of alcoholics are also at risk for other substance use disorders.
Adoption studies and twin studies have shown that alcoholism concordance among identical twins is twice that of fraternal. The Danish Adoption Study (1974), in which adopted sons of alcoholics were raised by non-alcoholic foster parents, showed that these children still had increased risk of alcoholism.
Sons of alcoholics show a number of physiological abnormalities, including abnormal EEG's associated with drinking compared with normal subjects and other abnormal brain wave studies (such as evoked potentials). In addition, there exist abnormal hormonal response patterns in sons of alcoholics.
Some genetic differences may relate to inherited variations in the rate of metabolism. For example, decreased gastric oxidation of alcohol in women causes a higher blood alcohol level (BAL) in woman than in men. There has also been report of an association with a mutation on the D2 dopamine receptor gene on chromosome 11. This likely acts not as "causer," but rather a modifier.
Psychoactive effects relate to the direct effect of drug on receptors in the central nervous system. Thus, it is important to understand the pharmacokinetics of a drug: its routes of administration, absorption, metabolism, binding capacity, and excretion. Receptors have been identified for a number of substances—caffeine and cannabis, for example. Others substances act more nonspecifically—alcohol and inhalants, for example, act by dissolving into cell membranes, particularly in the central nervous system.
Pharmacodynamics: the following substances are listed with their receptors:
- Caffeine: adenosine
- Cannabis: THC receptor
- Hallucinogens: serotonin, NMDA
- Nicotine: nicotinic cholinergic receptors
- Opioids: opioid receptors
- Phencyclidine: NMDA
- Sedatives: chloride channel (GABA receptor)
Alcohol is generally thought to act by dissolving into cell membranes, specifically in the central nervous system. There is also some evidence that alcohol may potentiate the effects at neural synapses with GABAA receptors, similar to drugs such as benzodiazepines. Compared to benzodiazepines and other similar sedative drugs, however, alcohol use requires higher blood concentrations to achieve a comparable level of intoxication. Blood alcohol levels represent the concentration of alcohol in the blood and are typically measured in acutely intoxicated patients presenting for medical care (such as in emergency departments). The rate of increase in BAL is inversely related to the rate of gastric emptying; hence the reason for not drinking on an empty stomach. About 90% of patients with a BAL greater than 0.15% will show gross intoxication (with symptoms involving speech and gait), loss of consciousness can occur at 0.30%, and respiratory depression may be seen at about 0.45% (potentially resulting in death). Other acute effects of alcohol at the cellular level include ADH antagonism (the “happy hour diuresis”), potentiation of gastric acid secretion (increasing the risk for gastritis), increased peripheral vasodilation and flushing (a centrally-mediated effect), and increased levels of HDL, triglycerides, and uric acid.
Alcohol metabolism follows zero-order kinetics, meaning that a constant amount of the substance is metabolized per unit of time. The steps involved in hepatic alcohol metabolism are as follows:
Ethanol acetaldehyde acetate
The enzymes involved in this reaction are alcohol dehydrogenase (1st step) and acetaldehyde dehydrogenase (2nd step). As noted above, in women the rate of activity of alcohol dehydrogenase is lower, thus causing increased BAL levels. Alcohol metabolism can also be modified by hepatic microsomal enzymes that use NADPH. Acutely, alcohol use can inhibit hepatic p450 enzymes, thus transiently increasing the levels of concurrently taken drugs such as diazepam. With chronic use, however, alcohol can induce hepatic p450 enzymes, thus causing an increase in its own metabolism along with other drugs eliminated by this route. This may provide one cellular-based mechanism of tolerance that occurs with long-term users.
Cocaine acts in the brain by inhibiting catecholamine reuptake, thus increasing the availability of DA and NE in the synaptic cleft. As described above, the potentiation of DA activity in regions of the brain such as the nucleus accumbens may be responsible for cocaine’s addictive properties as well as its euphoriant effects. Dopaminergic activity is thought to also underlie the hallucinations (often tactile) sometimes seen during cocaine intoxication. Additionally, increased NE activity in the brain may cause symptoms of psychomotor agitation, including stereotypic or repetitive behaviors such as pacing, nail-biting, and scratching. This may be related to the binding of cocaine in areas such as the caudate nucleus. In addition, cocaine has peripheral effects on the body, augmenting sympathetic nervous system activity and causing tachycardia, pupillary dilation, and hypertension. Cocaine-mediated vasoconstriction can also produce angina, and in rarer instances, sudden cardiac death. Note that the effects of other substances on the body, particularly amphetamines, can mimic cocaine intoxication. Amphetamines enhance the release of NE and DA from the axon terminal, thus working similar to cocaine by increasing their availability in the synaptic cleft.
Receptors: Nicotine in tobacco exerts its actions on physiology and behavior by binding to nicotinic acetylcholine receptors (nAChRs), ion-gated channels that are normally responsive to endogenous acetylcholine. These receptors are found in the central nervous system and in the periphery (ANS, neuromuscular junction), and they are all involved in the physiological responses to tobacco. Each class of receptors generally contains different subunits, and experiments using gene knockout mice have indicated that certain subunits are specifically implicated in nicotine dependence. In time, this information may help to understand individual differences in response to nicotine and therefore nicotine dependence (e.g., those smokers with more or less of the specific nicotinic receptors), and it might help in tailoring new pharmacologic treatments which specifically target these receptors (e.g., by blocking or antagonizing their function, making nicotine less reinforcing).
It is also important to understand the dynamics of receptor function in relation to smoking and blood/brain nicotine levels. Neuroreceptors can become more sensitive for various reasons and they can also proliferate, both of which can be referred to as upregulation. Typically, one observes upregulation of receptors as a compensatory response to low levels of a neurotransmitter. Downregulation refers to the opposite, reduced sensitivity or fewer receptors, which in turn serves to compensate for excess levels of a neurotransmitter.
In the case of nicotinic receptors, the story is a little more complicated, and can be explained as follows: upon smoking a cigarette, a small pulse of nicotine activates nAChRs that directly or indirectly induce dopamine release, thus providing a pleasurable effect. With continued use, nicotine builds up to a slow steady-state concentration that causes significant nAChR desensitization and, over time, inactivation. There is evidence that nicotinic receptor turnover decreases following inactivation, leading to an increased number of nAChRs. In between cigarettes, during sleep, or under conditions of abstinence while attempting to stop smoking, nicotine levels drop and a portion of the inactive nAChRs recover to a responsive state. Because of the increased number of nAChRs that have now become responsive, some cholinergic systems become hyperexcitable to acetylcholine, contributing to the drive for the next cigarette. Thus, smokers may medicate themselves with nicotine to regulate the number of functional nAChRs. Note that this is still only a theoretical model, but it explains the powerful reinforcement experienced when smoking after a period of abstinence, even overnight. Understanding receptor function can also explain the rapid development of tolerance to nicotine’s effects, which would drive continued smoking.
Effects on the body: The effects of nicotine on the body are widespread. In the CNS, nicotine causes direct activation of ACh receptors, which when activated in regions such as the hippocampus can improve short-term memory and cognition/attention. Additionally, via activation of ACh receptors, nicotine can potentiate the release of dopamine (promoting its addictive properties, as described above), NE (promoting stimulation and arousal), and endogenous opioids (promoting stress-reducing and analgesic effects). There is also evidence that a component of tobacco (not nicotine) may inhibit the enzyme monoamine oxidase (MAO), which normally breaks down neurotransmitters such as dopamine, serotonin, and norepinephrine. Peripheral effects of nicotine are considerable and include increased heart rate, increased blood pressure, vasoconstriction, increased metabolic rate and lipolysis, skeletal muscle relaxation, and increased ACTH release and adrenal steroid production. Nicotine is rapidly cleared from the brain, and has a short half-life in the blood (with p450 liver metabolism to cotinine, the active metabolite), both which are factors that could partially account for the need for constant dosing.
Classes of psychoactive substances recognized in DSM-IV include alcohol, amphetamines and related drugs, caffeine, cannabis, cocaine, hallucinogens, inhalants, nicotine, opioids, phencyclidine and related drugs, and sedatives. Polysubstance abuse occurs in which three or more categories of drug are abused (not including nicotine). Other drugs of abuse can include steroids, nitrates, and anticholinergics, to name a few. The criteria for diagnosis are as follows:
Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) DefinitionsEdit
DSM-IV defined Substance Dependence is a maladaptive pattern of substance use. Criteria for diagnosis include three of following over a 1 year period:
- Use in larger amounts than intended
- Persistent desire or unsuccessful attempts to cut down
- Time spent in activities necessary to get substance, taking substance or recovering from its effects.
- Social, occupational or recreational activities given up as a result of the substance
- Continued substance use despite knowledge of having a problem
Note that these patients don't need to have physical dependence. The definition of substance dependence is basically equivalent to "addiction," which is not used in DSM.
DSM-IV Substance Abuse is a maladaptive pattern of substance use leading to impairment. Criteria include one or more of following over 12 months:
- recurrent substance use resulting in a failure to fulfill role obligations (work, school, home)
- hazardous use (driving while intoxicated)
- related legal problems
- continued use despite persistent problems relating to the substance
It is important in the case of substance abuse to rule out substance dependence (which takes precedence).
DSM-IV Substance Intoxication is a reversible substance-specific syndrome due to recent exposure to a substance. Maladaptive behaviors or psychological changes can develop due to the substance and are not due to another medical/mental condition.
DSM-IV Substance Withdrawal is a substance-specific syndrome due to cessation or reduction in substance use that has been heavy and prolonged. Withdrawal causes distress/impairment, and is not due to another medical/mental condition.
Aside from classification according to DSM-IV criteria, other schemas of substance use/abuse exist as well. One such schema includes alcohol patterns. The so-called "alpha" pattern is one of continual excessive use when under stress, with no dependence and no loss of control. The "beta" pattern is one of heavy social drinking with physical complications, such as cirrhosis, but no dependence. The "delta" pattern is that of heavy daily drinking, but no loss of control. This is the more common type in Europe, for example in France. The "epsilon" pattern is defined as binge drinking, and the "gamma" pattern is that of physical dependence with loss of control. This is a more common type in the US.
Diagnostic tools for detecting alcoholism include administering the CAGE Questionnaire, and collecting other relevant historical data.
- The CAGE Questionnaire:
- Have you ever felt the need to Cut down on your drinking?
- Have you ever felt Annoyed by criticisms of your drinking?
- Have you ever had Guilty feelings about your drinking?
- Have you ever taken a morning Eye opener?
Some historical “red flags” might include (1) a pattern of unexplained job changes; (2) vague, defensive or evasive responses to alcohol-related questions; (3) DUI convictions; or (4) multiple unexplained traffic accidents. In addition, patients with alcoholism may have a history of impulsive behavior, fighting, or falls and scrapes, blackouts, binge drinking, or delirium tremens (DT’s). A history of drinking to relax or sleep is significant, as is a history of family chaos and instability. Relevant physical data to collect include the obvious stigmata of alcohol or drug use. For alcohol use, this may include spider angiomas, ruddy nose and face, peripheral neuropathies, liver disease, or cerebellar dysfunction. Additionally, patients may experience symptoms of gastric irritation related to acute or chronic alcohol use. For other drugs, this may be cutaneous abscesses and track marks (in IV drug abusers), or nasal lesions (cocaine).
Relevant laboratory data to collect for diagnostic purposes in alcoholism include a complete blood count and liver enzymes. Lab abnormalities may relate to malnutrition and organ damage, and may be expressed as leukopenia, macrocytic anemia, target cells (liver damage), thrombocytopenia, and bone marrow suppression. CAMP (cyclic adenosine monophosphate) levels in white blood cells of alcoholics are three times normal. Liver enzymes are abnormal in chronic alcoholism. Substance use can be easily detected via toxicology screens, in which urinary metabolites of several drugs are measured. It is important to observe directly the sample collection process. In addition, it is important to note the risk of false positives. One needs to confirm findings with a second test on the same sample using different analytic method (for example, poppy seed ingestion can cause false positive screens for opiates). Informed consent is crucial in toxicity screens.
"Normal use" is the main component in the differential of substance abuse. However, this brings up the question of what is normal. Perhaps the most important differential is between those patients who are addicted to drugs, and those who are merely physically dependent. The difference lies in the definition of addiction. For example, a patient with chronic pain, who is using regular opioids to alleviate pain, is probably physically dependent on the opioids, in the sense that the patient is probably tolerant to opioids, and would likely go into withdrawal if the opioids were suddenly stopped. However, such a patient does not necessarily show the compulsive behaviors associated with addiction. Furthermore, if the patient is taking the opioids for their analgesic, rather than euphoriant effects, then one cannot really say that the patient is addicted to antidepressants. Other differentials to consider in a patient with suspected substance abuse includes delirium along with other Axis I psychiatric conditions (which are often comorbid).
Comorbid Disorders And ComplicationsEdit
Withdrawal. Though generally uncomplicated, alcohol withdrawal can progress to delirium tremens (DTs), 10% of which are fatal. It is important to understand the differences between uncomplicated withdrawal and delirium tremens. Also, note that the hallucinations found in both of the above conditions are typically visual or tactile in nature, which may be distinguished from the auditory hallucinations of a distinct entity termed alcohol hallucinosis (described later).
Seizures. Seizures are common with high levels of alcohol use, independent of withdrawal.
Alcoholic Hallucinosis. Hallucinations can occur after drinking cessation in patients with alcohol dependence. These occur in a clear sensorium, and are not part of DTs. They are usually auditory hallucinations with persecutory content, and they can become chronic. Wernicke's encephalopathy: An acute neurological syndrome associated with long term alcohol abuse, the condition consists of delirium and the following triad of symptoms: ataxia, nystagmus and opthalmoplegia. It is thought to result from the thiamine deficiency that can result from chronic alcoholism. The treatment is, of course, to give thiamine (typically, it is given with folate).
Dementia. Dementia is common in patients with alcoholism. Most classic is the Korsakoff's Dementia (sometimes called Korsakoff's Psychosis, but that is a misnomer). This is characterized by an extremely poor short term memory--much worse than with Alzheimer's. Often associated with the memory losses are confabulations, though this is nonspecific to any dementia. More common is a more "run of the mill" type of dementia; usual called simply alcohol dementia, or dementia due to alcohol dependence. There remains some debate as to whether the dementia associated with alcoholism is due to a neurotoxic effect of alcohol itself, or to accessory problems (e.g., malnutrition, vitamin deficiencies).
The dementia associated with alcoholism is most likely irreversible. In the case of Korsakoff’s, the thiamine and folate are usually given, which do generally improve the Wernicke’s syndrome, but the memory disorder generally remains.
Fetal Alcohol Syndrome. FAS is due to heavy alcohol use during pregnancy. There is a high incidence in alcoholic mothers. Seventeen percent of births to alcoholic mothers are stillborn or die shortly after birth. Twenty percent have some defects, and 32% show fetal alcohol syndrome. Of those children with fetal alcohol syndrome, less than 6% are able to function normally in schools, and most never hold a job. (see is link for FAS
Withdrawal from other drugsEdit
Unlike alcohol withdrawal, the course of withdrawal is generally not life-threatening in most of the other drugs of abuse described above. However, withdrawal in these instances may be very uncomfortable for the patient. Nicotine, for example, causes symptoms of irritability, headache, anxiety, increased heart rate, cravings, and (most concerning for many) weight gain. Women tend to gain more weight than men do during withdrawal. Most symptoms send to subside within two weeks on average, with considerable variability, but cravings and appetite increases may persist for much longer periods of time. Cocaine withdrawal also produces a number of symptoms, including hypersomnolence, fatigue, depression, intense cravings, and in some cases, suicidality. Note that the course of benzodiazepine withdrawal can mimic that of alcohol withdrawal (including seizures, DTs, or death), as both substances utilize biochemical mechanisms of action. Thus, benzodiazepine detoxification is approached with the same vigilance as in patients withdrawing from alcohol.
ECA data suggested that 53% of those with a substance disorder had a comorbid mental disorder. Some of these mental disorders include antisocial personality disorder (11x higher than the general public), anxiety disorders (panic disorder, generalized anxiety disorder, and phobias), and depression. Most often, depression is secondary to alcoholism. It generally improves with abstinence, though some dysphoria may remain. Depression affects 13% of female alcoholics. Alcoholism is also more common in patients with schizophrenia and bipolar disorder. Attention Deficit Disorder may predispose to alcoholism, but this is a controversial topic.
General principles dictate that alcoholism is often worse if familial. There are probably high incidences of (unreported) spontaneous remission. This complicates evaluation of different treatments. Drug abuse patterns are influenced by social and cultural factors and, compared with alcohol abuse, fluctuate over time.
Alcoholism typically has an exacerbating and remitting course, with periods of relative or complete abstinence. 2-3% of alcohol dependents become abstinent per year. Onset of alcoholism rarely begins after 45. Thirty percent of college problem drinkers are alcohol dependent 20 years later. The first hospitalization for alcohol tends to occur earlier in men (age 30 to 40). Abuse of cocaine and stimulants has a rapidly progressing course: from use to abuse and dependence. This is particularly true when the drugs are administered by the more potent routes (injection, inhaled). Oral and intranasal routes of ingestion show slower progression. Cannabis use rarely progresses to abuse and dependence if used alone. Hallucinogens very rarely progress to dependence. Opioid dependence represents a lifelong, chronic pattern. Abuse of sedative hypnotics can remit, either spontaneously or with treatment.