Chapter 9: Drug Abuse and Addiction

Transcription

1 Chapter 9: Drug Abuse and Addiction Drug use and abuse- some history Drug addiction: Defining terms Physical dependence/ drug withdrawal Factors that influence development and maintenance of drug addiction 2

2 Recreational Drug Use vs Drug Addiction Psychoactive drugs have been a part of human culture since antiquity. Many animal species will ingest psychoactive substances Many psychoactive substances (nicotine, caffeine, morphine, cocaine, THC), are made by plants and were available to ancient peoples. A 2011 US Survey on Drug estimated that 8.7% of population were current users of illicit drugs. Legal drugs such as tobacco and alcohol are consumed even more widely. YET occasional recreational use can transition to frequent, habitual use in spite of adverse health/social/familial/occupational consequences The paradox of addiction: How can a person develop and maintain a pattern of behavior that is so obviously destructive to his or her life? 3 No one has a complete explanation for this paradox, though many theories have been proposed.

3 Psychoactive Drugs, Society and the Law: some (U.S.) history 200 years ago, only alcohol, tobacco, and opium were readily available in North America. Alcohol temperance movement that culminated in prohibition equated drug use with criminal behavior. Advances in chemistry lead to more concentrated forms (e.g., morphine was purified from opium, and cocaine from coca) and delivery (e.g., hypodermic needles) enabled drugs to be more addictive Lack of drug control laws resulted in psychoactive drugs used in tonics and medicines. Heroin was synthesized by Bayer Laboratories in 1874 and was first marketed as a non-addicting (!) substitute for codeine to control coughs Coca leaves were used in Coca-Cola's preparation and small amount of cocaine present in the product gave the drinker a "buzz During the 20 th century, federal government increasingly controlled commercialization of drugs Pure Food and Drug Act (1906) = labeling of medicines Harrison Act (1914) = controlled the use of opiates and cocaine, prohibiting non-medical use For Canadian history of drug laws, see : 4

4 Psychoactive Drugs, Society and the Law: some (U.S.) history In the second half of the 20 th century, drug addiction came to be viewed as a disease to be treated by the medical establishment. Alcoholism declared a disease by the World Health Organization and the American Medical Association. The federal government became more involved in drug regulation as a result of increased drug use or perceived societal danger of drug use. 1970: Controlled Substance Act replaced/updated previous legislation: established five schedules of controlled substances, and created Drug Enforcement Agency (DEA). 1980: War on Drugs triggered increased potency of illegal drugs (and new drugs)- yet- Illegal drug use continues on a massive scale Existing laws are not consistent with scientific evidence (e.g., nicotine is more addictive than marijuana). Laws have limited ability to prevent drug abuse. 5

5 Psychoactive Drugs, Society and the Law: some (U.S.) history An example: marijuana Use dates back 6000 years ago to Far East One story about Muslim sect headed by Hashishin-i- Sabbah Story goes Hashishin would send out assassins and reward them with cannabis (but was likely opium) Hemp plant was big cash crop, used for rope and other products Psychoactive effect introduced in U.S. in early 1900 s In 1926, report in New Orleans newspaper exposes menace of marijuana : claims that drug turns normal people into violent drug-crazed criminals (??) who become heroin addicts U.S. gov t enacts Marijuana Tax Act (1937) banned nonmedical use of cannabis- eventually drug listed as narcotic 6

6 Addiction, What Is It? Addiction is complex, a precise definition is difficult Many people take psychoactive drugs recreationally, but even if drug use is quite frequent, they can control their intake: heavy drug use does not necessarily mean the person is an addict. Multiple factors need to be considered to assess if individual is addicted to drugs Habitual drug use that persists in spite of the adverse effects it has on health and social life o o Individuals remain addicted for long periods of time, and drug-free periods (remissions) are often followed by relapses in which drug use recurs, despite negative consequences. May be viewed as a chronically-relapsing disorder Drug seeking behaviour: a disproportionate amount of time spent thinking about (craving) and acquiring the drug o Certain environmental triggers can prompt craving/relapse Physical Dependence: do they suffer from withdrawal symptoms after drug use that may motivate them to return to using 7

7 Drug Withdrawal: Body s reaction to elimination of drug from system after repeated exposure. Reactions are typically the opposite of the drugs action (e.g.: after prolonged exposure to sleeping pills, withdrawal causes insomnia) o Body initiates compensatory physiological changes to counter drug effects and try to maintain homeostasis o When drugs have been eliminated from system, these changes can linger for sometime after = [withdrawal symptoms] Additional drug taking can reduce withdrawal symptoms o Sometimes, cues associated with drug taking can trigger withdrawal-like symptoms (conditioned withdrawal) Withdrawal may contribute to relapse, but unlikely to be a primary factor involved in maintaining long lasting effects of addiction. Withdrawal last for a few days at most, but addiction can last a lifetime Note differences between physical and psychological dependence A drug may not cause physical dependence, but people take it repeatedly to escape from other problems in their lives (an example of self-medication). 8

8 Addiction- medical definitions Because the term addiction has conflicting definitions and strong negative associations, the American Psychiatric Association stopped using the terms addiction and addict. The Diagnostic and Statistical Manual of Mental Disorders (DSM) defines substance-related disorders as: The individual has manifested a maladaptive pattern of substance use for at least 12 months that has led to significant impairment or distress, by clinical standards. At least two additional criteria must be met: 1. Continuing to use drugs despite negative personal consequences 2. Repeatedly unable to carry out major obligations at work, school, or home due to drug use 3. Recurrent use of drug in physically hazardous situations 4. Continued use despite persistent or recurring social or interpersonal problems caused or made worse by drug use 5. Tolerance as defined by either a need for markedly increased amounts to achieve intoxication or desired effect or markedly diminished effect with continued use of the same amount 6. Withdrawal manifesting as either characteristic syndrome or the substance is used to avoid withdrawal 7. Using greater amounts or using over a longer time period than intended 8. Persistent desire or unsuccessful efforts to cut down or control drug use 9. Spending a lot of time obtaining, using, or recovering from using drug 10. Stopping or reducing important social, occupational, or recreational activities due to drug use 11. Consistent use of drug despite acknowledgment of persistent or recurrent physical or psychological difficulties from using opioids 12. Craving or a strong desire to use 9

9 (Simpler) Theories of Drug Addiction Physical Dependence Model: Addicts take drugs to get rid of withdrawal symptoms Problems: Many times addicts relapse when withdrawal symptoms have passed; some drugs do not have severe withdrawal symptoms (i.e.: cocaine) Detoxified addicts (drugs eliminated from system) still remain addicted Treatments used to curb withdrawal (e.g. nicotine patch) are not 100% effective Positive Reward Model: addicts take drugs for the pleasurable feelings Problems: addicts can continue to take drugs and seek them out even if they are no longer giving as good a rush they have felt in the past (i.e.: tolerance to the hedonic effects have occurred) Some drugs (eg; nicotine) do not give as much of a euphoric rush as other drugs (eg: heroin) but are just as addictive 10 10

10 Factors that Influence Development/Maintenance of Addiction (I) Theory: (Koob and Le Moal, 2005) drug-taking behavior progresses initially from an impulsive stage Primary motivation is drug s positive reinforcing effects With repeated use, it transitions to compulsive stage In compulsive stage, primary motivation is relief from drug withdrawal. Over time, an addict may undergo many episodes of withdrawal. Stimuli associated with drug taking can trigger conditioned withdrawal, which may promote relapse and more drug taking. Note again that even though withdrawal certainly can contribute to drug cravings and maintenance of addiction, it cannot explain all aspects of the behavior 11

11 Factors that Influence Development/Maintenance of Addiction (II) Route of Administration influences addiction potential of a substance Intravenous injection or inhalation yields rapid drug entry into the brain and fast onset of drug action Oral/transdermal routes results in relatively slow absorption Fast onset is associated with shorter duration of action and is more likely to produce addiction. IV and inhalation produce the strongest euphoric effects as a result of rapid drug delivery to the brain. Repeated exposure to rapid delivery may produce long-term neurobiological changes needed for addiction to develop. 12

12 Factors that Influence Development/Maintenance of Addiction (III) Many individuals who take drugs once or a few times stop before developing compulsive patterns of drug taking True even for highly reinforcing drugs like cocaine and heroin. Thus, additional factors contribute to the development of addiction. Genetic variation may contribute to vulnerability to addiction: Polymorphisms of alleles of certain genes can influence susceptibility to developing substance abuse disorders in certain individuals. These variations change the function of the protein the gene encodes for, may increase or decrease its activity that in turn can alter how it affects neural activity or responses to drug Majority of research on genetics and addiction has focused on alcoholism Genetic studies:... 55% MZ twins, 28% DZ twins are concordant for alcoholism if father is alcoholic 25% of sons, 5-10% of daughters likely to become alcoholics 13

13 Alcoholics tend to have higher tolerance, metabolize EtOH quicker, related to levels of the enzyme that metabolizes EtOH (alcohol dehydrogenase) Other genes polymorphisms implicated in increased risk for alcohol addiction include: GABA-A receptor subunits 5-HT transporter Dopamine D4 receptors Opioid receptor Addiction Genetics For tobacco addition, susceptibility genes include those coding for enzymes involved in nicotine metabolism and nicotinic receptors Even in laboratory animal populations, there are individual differences in susceptibility to developing addictive like patterns of drug intake (more on that later.) 14

14 Factors that Influence Development/Maintenance of Addiction (IV) Personality variables- which may be influence by genetics or environment also linked to addiction susceptibility Behavioral disinhibition: Substance abuse is linked to a cluster of traits: impulsivity, antisociality, and aggressiveness, combined with low levels of constraint and harm avoidance. Stress reduction: High scores on traits like stress reactivity, anxiety, and neuroticism are indicative of heightened vulnerability to addiction. Reward sensitivity: Drug abuse is related to sensation seeking, reward seeking, extraversion, and gregariousness. Individuals scoring high on these traits would seek out drugs for their positive-reinforcing qualities. 15

15 Factors that Influence Development/Maintenance of Addiction (IV) Psychosocial variables also contribute to addiction risk: Stress and stress-coping mechanisms; treatment for addiction often includes learning new coping skills. Addiction often co-occurs with other anxiety, mood, or personality disorders (comorbidity). Self-medication hypothesis: Stressful life events could trigger anxiety and mood disorders, such as depression, which in turn could lead to substance use in an attempt at self-medication. A biopsychosocial model of addiction includes pharmacological, biological, and psychological/ sociocultural factors that influence addiction risk. Some factors promote the likelihood of addiction and others reduce it 16