Medical School · Year 2 · Psychiatry · includes a quiz and discussion video

Lecture 6: Substance Use Disorders

Unit 2.6: Psychiatry

Learning Objectives

By the end of this lecture, students will be able to:

1. Describe the diagnostic criteria for substance use disorders
2. Explain the neurobiology of addiction
3. Describe alcohol use disorder and its management
4. Explain opioid use disorder and medication-assisted treatment
5. Describe stimulant and other substance use disorders
6. Explain motivational interviewing and stages of change

Lecture Outline

I. Substance Use Disorders: Framework and Diagnosis

The DSM-5 approach to substance use disorders represents a significant change from previous editions, combining the former categories of substance abuse and substance dependence into a single diagnostic category termed substance use disorder. The severity of the disorder is determined by symptom count, with mild substance use disorder defined by two to three criteria, moderate by four to five criteria, and severe by six or more criteria. This dimensional approach better captures the spectrum of problematic use and has improved reliability.

The eleven diagnostic criteria for substance use disorders are organized into four clusters. The impaired control cluster includes using larger amounts or for longer than intended, persistent desire or unsuccessful efforts to cut down or control use, spending a great deal of time obtaining, using, or recovering from the substance, and craving or strong desire to use. The social impairment cluster includes failure to fulfill major role obligations, continued use despite persistent social or interpersonal problems, and giving up or reducing important activities. The risky use cluster includes recurrent use in physically hazardous situations and continued use despite knowledge of physical or psychological problems caused by the substance. The pharmacological cluster includes tolerance and withdrawal.

The epidemiology of substance use disorders reveals significant public health impact. Alcohol use disorder affects approximately fourteen percent of the population over their lifetime, making it the most prevalent substance use disorder. Tobacco use disorder affects roughly twenty percent of adults and represents the leading preventable cause of death. Cannabis use disorder affects approximately three percent. Opioid use disorder affects about one percent but causes disproportionate mortality. Stimulant use disorders affect approximately half a percent of the population.

Comorbidity between substance use disorders and other psychiatric conditions is exceedingly common. Depression, anxiety disorders, PTSD, bipolar disorder, and ADHD all show high rates of co-occurrence with substance use. The relationship is bidirectional, with psychiatric disorders increasing vulnerability to substance use and substance use worsening psychiatric symptoms. Medical comorbidities including liver disease, cardiovascular disease, and infectious diseases add complexity to treatment. The term dual diagnosis refers to the co-occurrence of substance use disorder with another mental illness.

<image>Panel A illustrates the DSM-5 severity spectrum as a gradient from mild (2-3 criteria) through moderate (4-5 criteria) to severe (6+ criteria), replacing the former abuse/dependence dichotomy. Panel B displays the eleven criteria organized into four clusters: impaired control (4 criteria with icons for increased use, failed attempts, time spent, craving), social impairment (3 criteria), risky use (2 criteria), and pharmacological (2 criteria for tolerance and withdrawal). Panel C presents prevalence data as a bar graph comparing alcohol (14%), tobacco (20%), cannabis (3%), opioids (1%), and stimulants (0.5%). Panel D shows comorbidity relationships as a network diagram connecting substance use disorders to depression, anxiety, PTSD, bipolar, ADHD, and medical conditions, with bidirectional arrows indicating mutual influence.</image>

II. Neurobiology of Addiction

The reward circuitry underlying addiction centers on the mesolimbic dopamine system. The ventral tegmental area contains dopamine neurons that project to the nucleus accumbens, the primary reward processing center. The prefrontal cortex provides top-down control over reward-seeking behavior and is critical for decision-making and impulse inhibition. The amygdala contributes to the emotional salience of drug-related cues and the conditioned responses that drive craving. These structures form an integrated circuit that is hijacked by addictive substances.

Drugs of abuse produce their reinforcing effects through massive dopamine release that far exceeds that produced by natural rewards. Natural rewards such as food and sex produce modest dopamine increases that signal salience and promote survival-relevant learning. Addictive drugs produce immediate, intense dopamine surges that powerfully reinforce drug-taking behavior. No natural satiation occurs with drug reward, unlike the diminishing returns seen with repeated natural reward. This pharmacological reward signal overwhelms the normal learning and motivation systems.

Neuroadaptation occurs with repeated drug exposure and underlies tolerance, sensitization, and withdrawal. Tolerance develops as receptors downregulate and neurons adapt to the presence of the drug, requiring increased doses to achieve the same effect. Sensitization refers to enhanced reactivity to drug-related cues that can persist long after drug cessation. Withdrawal occurs when the adapted system is deprived of the drug, producing a state opposite to the drug's acute effects. Allostatic shift describes how the set point for well-being changes such that the drug becomes necessary just to feel normal.

Brain changes with chronic addiction are persistent and contribute to relapse vulnerability. Prefrontal cortex dysfunction impairs decision-making and self-control, reducing the ability to resist drug-seeking despite known consequences. Habit formation shifts control from the ventral striatum to the dorsal striatum, making drug-seeking automatic rather than goal-directed. Stress system dysregulation through CRF and norepinephrine contributes to negative emotional states during abstinence. Persistent cue-drug associations create memories that can trigger craving years after last use.

<image>Panel A displays the reward circuit in a brain diagram showing the ventral tegmental area projecting to the nucleus accumbens (reward processing), with connections to the prefrontal cortex (top-down control) and amygdala (emotional salience and cue reactivity). Panel B contrasts dopamine release with natural rewards (modest, gradual increase with satiation) versus drugs of abuse (massive, immediate spike with no satiation), showing how drug-induced release overwhelms the system. Panel C illustrates neuroadaptation processes: tolerance (receptor downregulation requiring more drug), sensitization (enhanced cue reactivity persisting over time), withdrawal (opponent process when drug absent), and allostatic shift (new set point requiring drug for normal function). Panel D shows brain changes in addiction: PFC dysfunction (impaired decision-making), habit formation (shift from ventral to dorsal striatum), stress system dysregulation (CRF, norepinephrine), and persistent cue-drug memories triggering relapse.</image>

III. Alcohol Use Disorder

Alcohol use disorder represents the most common substance use disorder, with approximately fourteen percent lifetime prevalence. Men are affected more frequently than women. Mortality associated with alcohol use disorder reaches approximately eighty-eight thousand deaths annually in the United States, making it the third leading preventable cause of death. Medical consequences span multiple organ systems including liver disease, cardiovascular effects, neurological complications, and increased cancer risk.

At-risk drinking is defined using specific quantity thresholds that identify individuals at elevated risk before they meet criteria for alcohol use disorder. For men, at-risk drinking is defined as more than fourteen drinks per week or more than four drinks on a single occasion. For women and adults over sixty-five, the thresholds are more than seven drinks per week or more than three drinks per occasion. A standard drink is defined as containing fourteen grams of pure alcohol, equivalent to twelve ounces of regular beer, five ounces of wine, or 1.5 ounces of distilled spirits.

Alcohol withdrawal occurs when alcohol-dependent individuals abruptly reduce or stop drinking. The timeline of withdrawal symptoms is predictable: tremor, anxiety, insomnia, nausea, and tachycardia emerge six to twelve hours after the last drink; hallucinations, typically visual or tactile, may occur at twelve to twenty-four hours; withdrawal seizures peak at twenty-four to forty-eight hours; and delirium tremens, characterized by altered mental status, autonomic instability, and hallucinations, develops at forty-eight to ninety-six hours in severe cases. Alcohol withdrawal can be life-threatening and requires careful medical management.

The Clinical Institute Withdrawal Assessment for Alcohol (CIWA-Ar) provides a standardized tool for assessing withdrawal severity. The scale evaluates nausea and vomiting, tremor, sweating, anxiety, agitation, tactile disturbances, auditory disturbances, visual disturbances, headache, and orientation. Scores above eight to ten typically indicate need for pharmacological treatment. The CIWA-Ar can be used to guide symptom-triggered dosing of benzodiazepines, which has been shown to reduce total benzodiazepine dose and treatment duration compared to fixed-schedule dosing.

<image>Panel A presents alcohol use disorder epidemiology: 14% lifetime prevalence, 88,000 annual deaths, medical consequences affecting liver (cirrhosis), heart (cardiomyopathy), brain (Wernicke-Korsakoff), and cancer risk. Panel B displays at-risk drinking thresholds as a comparison diagram: men (more than 14/week or 4/occasion) versus women and elderly (more than 7/week or 3/occasion), with standard drink equivalents shown. Panel C illustrates the withdrawal timeline: 6-12 hours (tremor, anxiety, insomnia), 12-24 hours (hallucinations), 24-48 hours (seizure risk peak), 48-96 hours (delirium tremens risk). Panel D shows the CIWA-Ar assessment with the ten domains rated and a threshold indicator for treatment initiation at score 8-10, demonstrating symptom-triggered benzodiazepine protocol.</image>

IV. Alcohol Use Disorder Treatment

Withdrawal management begins with benzodiazepines as first-line treatment, which reduce withdrawal symptoms and prevent seizures and delirium tremens. Symptom-triggered dosing using the CIWA-Ar protocol allows benzodiazepine administration based on objective symptom severity. Fixed-schedule dosing with additional doses as needed is an alternative approach. Thiamine administration is essential to prevent Wernicke encephalopathy and must be given before glucose administration to avoid precipitating this condition. Folate, multivitamins, and fluid and electrolyte correction address common nutritional deficiencies.

Several FDA-approved medications are available for maintenance treatment of alcohol use disorder. Naltrexone is an opioid antagonist that reduces craving and the reinforcing effects of alcohol, available in oral daily formulation or monthly extended-release injection. Acamprosate modulates glutamate and GABA systems and appears most effective for maintaining abstinence rather than reducing drinking in those still using. Disulfiram inhibits aldehyde dehydrogenase, causing an aversive reaction when alcohol is consumed; it requires significant patient motivation and should be used with caution due to potential severity of reactions.

Several off-label medications have evidence for treating alcohol use disorder. Topiramate has shown efficacy in reducing heavy drinking days through multiple mechanisms. Gabapentin may be particularly helpful in patients with prominent anxiety symptoms and has some evidence for reducing heavy drinking. Ondansetron shows benefit specifically in patients with early-onset alcoholism. Baclofen has evidence primarily from European studies but has been adopted in some treatment settings.

Psychosocial treatments are essential components of alcohol use disorder management. Motivational interviewing enhances motivation to change through a nonconfrontational, client-centered approach. Cognitive-behavioral therapy helps identify triggers and develop coping skills to manage urges and high-risk situations. Twelve-step programs such as Alcoholics Anonymous provide mutual support and a structured approach to recovery. Brief intervention using the SBIRT model (Screening, Brief Intervention, Referral to Treatment) is effective in medical settings for patients with at-risk drinking and mild to moderate alcohol use disorder.

<image>Panel A displays withdrawal management protocol: benzodiazepines as first-line with symptom-triggered or fixed-schedule dosing, thiamine before glucose (with warning sign), folate and multivitamins, and fluid/electrolyte correction. Panel B presents FDA-approved medications with mechanisms: naltrexone (opioid antagonist reducing craving, oral or monthly injection), acamprosate (glutamate/GABA modulation for abstinence maintenance), disulfiram (aldehyde dehydrogenase inhibition causing aversive reaction). Panel C shows off-label medications: topiramate (multiple mechanisms), gabapentin (especially with anxiety), ondansetron (early-onset alcoholism), baclofen (European evidence). Panel D illustrates psychosocial treatment components: motivational interviewing (readiness ruler), CBT (trigger identification and coping skills), 12-step programs (mutual support), and SBIRT in medical settings (screening → brief intervention → referral flow).</image>

V. Opioid Use Disorder

The opioid crisis represents a public health emergency, with overdose deaths exceeding one hundred thousand annually in the United States. The epidemic evolved through waves: initial increases related to prescription opioid overprescribing, subsequent rises in heroin use as prescription access tightened, and most recently dramatic increases in synthetic opioid deaths, particularly from fentanyl. Risk factors for opioid use disorder include chronic pain, psychiatric illness, prior substance use disorders, and genetic vulnerability.

Opioid intoxication produces characteristic findings that are essential to recognize. Central nervous system depression manifests as sedation, drowsiness, and confusion. Respiratory depression is the primary mechanism of death in overdose, with decreased respiratory rate and oxygen saturation. Pupillary constriction producing miosis is highly characteristic. Treatment of overdose centers on naloxone, an opioid antagonist that rapidly reverses opioid effects and can be life-saving when administered promptly.

Opioid withdrawal, while extremely uncomfortable, is not life-threatening in otherwise healthy adults, distinguishing it from alcohol and sedative withdrawal. Symptoms follow a predictable timeline: early symptoms at eight to twenty-four hours include anxiety, yawning, rhinorrhea, lacrimation, and sweating; peak symptoms at thirty-six to seventy-two hours include dilated pupils, piloerection, nausea, vomiting, diarrhea, and muscle aches. Resolution typically occurs over seven to ten days, though protracted withdrawal symptoms can persist for months.

The Clinical Opiate Withdrawal Scale (COWS) provides standardized assessment of withdrawal severity. Eleven items are assessed including resting pulse, sweating, restlessness, pupil size, bone or joint aches, runny nose or tearing, gastrointestinal upset, tremor, yawning, anxiety or irritability, and gooseflesh skin. Scores guide medication selection and timing, particularly important for buprenorphine induction which requires the patient to be in at least mild withdrawal to avoid precipitated withdrawal.

<image>Panel A presents the opioid crisis timeline showing waves of deaths: prescription opioids (rising from late 1990s), heroin (rising from 2010), synthetic opioids including fentanyl (dramatic rise from 2013), with current deaths exceeding 100,000 annually. Panel B displays opioid intoxication and overdose recognition: CNS depression (sedation), respiratory depression (decreased rate, hypoxia as primary death mechanism), miosis (pupil constriction), with naloxone as reversal agent. Panel C illustrates opioid withdrawal timeline: early symptoms at 8-24 hours (anxiety, yawning, rhinorrhea, lacrimation, sweating), peak symptoms at 36-72 hours (dilated pupils, piloerection, GI symptoms, muscle aches), resolution over 7-10 days, noting not life-threatening unlike alcohol withdrawal. Panel D shows the COWS assessment with eleven domains and scoring thresholds for mild, moderate, and severe withdrawal, with notation about buprenorphine induction timing.</image>

VI. Medication-Assisted Treatment for Opioid Use Disorder

Buprenorphine represents a first-line medication for opioid use disorder treatment. As a partial mu-opioid agonist, it produces ceiling effects for respiratory depression while providing sufficient agonist activity to suppress withdrawal and reduce craving. Formulations include sublingual tablets and films, buccal films, extended-release subcutaneous injection, and subdermal implants. Most formulations combine buprenorphine with naloxone, which deters injection misuse by precipitating withdrawal if the product is injected. Induction must occur when the patient is in mild withdrawal to avoid precipitated withdrawal. Office-based treatment is now possible without special waiver requirements, dramatically expanding access.

Methadone is a full mu-opioid agonist that has decades of evidence supporting its efficacy for opioid use disorder. As a full agonist, methadone carries greater risk of respiratory depression and overdose than buprenorphine. Distribution is restricted to federally licensed opioid treatment programs with daily supervised dosing initially, though take-home privileges can be earned with demonstrated stability. The long half-life provides stable blood levels and prevents the cycles of intoxication and withdrawal. QT prolongation is a significant consideration requiring ECG monitoring.

Naltrexone is a mu-opioid antagonist that blocks the effects of opioids, preventing any reinforcing effect if opioids are used. It is available as oral daily dosing or extended-release monthly intramuscular injection. A critical requirement is that patients must be opioid-free for seven to ten days before initiation to avoid precipitated withdrawal. Benefits include complete absence of abuse potential and elimination of diversion concerns. Limitations include the challenge of initiating treatment given the opioid-free requirement and adherence challenges with oral formulation.

Comparing the three medications reveals important differences. Buprenorphine and methadone as agonist therapies have demonstrated mortality reduction in randomized trials and observational studies. Naltrexone, when successfully initiated, also reduces mortality but the initiation challenge limits real-world effectiveness. Buprenorphine offers the advantage of office-based treatment and lower overdose risk. Methadone may be more effective for patients with severe use disorder but requires the structured OTP setting. Treatment selection should consider patient preference, severity, prior treatment response, and practical factors including access to different treatment settings.

<image>Panel A presents buprenorphine characteristics: partial mu-agonist mechanism with ceiling effect on respiratory depression, formulations (sublingual, buccal, injection, implant), buprenorphine-naloxone combination to deter injection, induction requirement for mild withdrawal, and office-based accessibility. Panel B displays methadone characteristics: full mu-agonist with respiratory depression risk, opioid treatment program requirement with daily dosing, long half-life providing stability, and QT prolongation requiring monitoring. Panel C shows naltrexone characteristics: mu-antagonist blocking opioid effects, oral and extended-release injection formulations, 7-10 day opioid-free requirement before initiation, no abuse potential, and adherence challenges. Panel D presents a comparison matrix of the three medications across efficacy, mortality reduction, setting, initiation requirements, abuse potential, and practical considerations.</image>

VII. Stimulant and Other Substance Use Disorders

Stimulant use disorder includes cocaine and methamphetamine as well as prescription amphetamines. Intoxication produces euphoria, increased energy and alertness, hyperactivity, dilated pupils, hypertension, and tachycardia. Psychosis with paranoid features is common with heavy use. Withdrawal produces a crash characterized by fatigue, depression, hypersomnia, and increased appetite. No FDA-approved medications exist for stimulant use disorder, making psychosocial interventions the mainstay of treatment. Complications include cardiovascular events, stroke, and severe dental disease with methamphetamine.

Cannabis use disorder has increasing prevalence as legalization spreads and perceptions of harm decrease. Intoxication produces euphoria, relaxation, altered time perception, perceptual changes, and increased appetite. Withdrawal is now recognized in DSM-5 and includes irritability, sleep disturbance, decreased appetite, and anxiety. Treatment relies on cognitive-behavioral therapy and motivational enhancement therapy. Concerns include the association between adolescent cannabis use and psychosis risk, as well as cognitive effects during critical developmental periods.

Sedative-hypnotic use disorder includes benzodiazepines, barbiturates, and Z-drugs such as zolpidem. Withdrawal is similar to alcohol withdrawal and can produce seizures and delirium, making it potentially life-threatening. Management requires gradual taper, often with substitution of a long-acting agent such as diazepam or phenobarbital. Cross-tolerance with alcohol has clinical implications for both intoxication and withdrawal.

Other substance classes include hallucinogens such as LSD, psilocybin, and mescaline, which produce perceptual disturbances and altered consciousness. Dissociatives including phencyclidine and ketamine can produce severe agitation and violence. Inhalants including solvents and nitrites carry risks of sudden death and neurotoxicity. MDMA produces empathogenic and mild hallucinogenic effects with risks of hyperthermia and serotonin toxicity.

<image>Panel A displays stimulant use disorder features: intoxication (euphoria, hyperactivity, dilated pupils, hypertension, tachycardia, possible psychosis), withdrawal (fatigue, depression, hypersomnia, increased appetite), no FDA-approved medications, and complications (cardiovascular, stroke, dental disease with methamphetamine). Panel B presents cannabis use disorder: intoxication (euphoria, relaxation, altered perception, increased appetite), withdrawal (irritability, sleep disturbance, decreased appetite, anxiety), treatment with CBT and MET, and concerns about psychosis risk and adolescent cognitive effects. Panel C shows sedative-hypnotic withdrawal compared to alcohol: similar timeline and risks (seizures, delirium), management with gradual taper using long-acting agents, and cross-tolerance with alcohol. Panel D illustrates other substance classes: hallucinogens (perceptual changes), dissociatives (agitation, violence risk), inhalants (sudden death, neurotoxicity), MDMA (hyperthermia, serotonin toxicity).</image>

VIII. Tobacco Use Disorder

Tobacco use disorder affects approximately fourteen percent of adults in the United States and represents the leading preventable cause of death. Nicotine dependence develops rapidly and is highly addictive, with most smokers making multiple quit attempts before achieving sustained abstinence. The Fagerström Test for Nicotine Dependence assesses dependence severity based on time to first cigarette, difficulty refraining in forbidden places, which cigarette is hardest to give up, cigarettes per day, smoking more in the morning, and smoking when ill.

Pharmacotherapy significantly improves quit rates and should be offered to all patients attempting cessation. Nicotine replacement therapy is available in multiple formulations including patches for steady-state nicotine delivery, gum and lozenges for acute craving relief, inhalers that address the behavioral component of smoking, and nasal spray for rapid nicotine delivery. Varenicline is a partial nicotinic receptor agonist that both reduces craving and blocks the rewarding effects of nicotine; it is the most effective single agent for smoking cessation. Bupropion, an NDRI antidepressant, is also effective and may be particularly useful in patients with comorbid depression.

The 5 A's provide a framework for tobacco intervention in clinical settings. Ask about tobacco use at every visit. Advise all tobacco users to quit in a clear, personalized manner. Assess willingness to make a quit attempt. Assist with counseling and pharmacotherapy. Arrange follow-up contact to support the quit attempt. This brief intervention, taking as little as three minutes, significantly increases quit rates.

Combination therapy often provides better outcomes than monotherapy. Combining a nicotine patch for steady-state replacement with a short-acting formulation for breakthrough cravings is more effective than either alone. Adding varenicline to nicotine replacement may provide additional benefit. The importance of behavioral support in conjunction with pharmacotherapy cannot be overstated, as combined approaches outperform either component alone.

<image>Panel A presents tobacco epidemiology and dependence: 14% adult prevalence, leading preventable cause of death, nicotine highly addictive with multiple quit attempts typical, and Fagerström Test domains for assessing dependence severity. Panel B displays pharmacotherapy options: nicotine replacement (patch for steady state, gum/lozenge for acute craving, inhaler for behavioral component, nasal spray for rapid delivery), varenicline (partial agonist, most effective), bupropion (NDRI, useful with depression). Panel C illustrates the 5 A's framework: Ask (every visit), Advise (clear quit recommendation), Assess (willingness to quit), Assist (counseling and pharmacotherapy), Arrange (follow-up). Panel D shows combination approaches: nicotine patch plus short-acting NRT for breakthrough, varenicline plus NRT, and behavioral support enhancing pharmacotherapy effectiveness.</image>

IX. Motivational Interviewing and Stages of Change

The transtheoretical model, or stages of change model, provides a framework for understanding readiness for behavior change. Precontemplation describes individuals not considering change, unaware of or unconcerned about the problem. Contemplation involves ambivalence, with the individual weighing pros and cons of change. Preparation indicates active planning to change, often with recent attempts. Action involves actively engaging in change behavior. Maintenance describes sustained change over time. Relapse, rather than being viewed as failure, is understood as a common part of the change process, with most individuals cycling through stages multiple times before achieving stable change.

Motivational interviewing is a client-centered counseling approach designed to enhance intrinsic motivation to change by exploring and resolving ambivalence. The core principles include expressing empathy through reflective listening and understanding the patient's perspective without judgment. Developing discrepancy involves helping patients see the gap between their current behavior and their broader goals and values. Rolling with resistance avoids argumentation and confrontation, instead exploring and reframing resistance. Supporting self-efficacy involves believing in and reinforcing the patient's ability to change.

The OARS technique provides the practical skills for motivational interviewing. Open-ended questions encourage exploration and elaboration rather than yes-no answers. Affirmations acknowledge the patient's strengths, efforts, and values. Reflections mirror and deepen the patient's statements, particularly those suggesting motivation for change. Summarizing pulls together themes from the conversation and can emphasize change talk.

Change talk represents patient statements indicating desire, ability, reasons, or need for change, as well as commitment to change. The DARN-C acronym captures these categories: Desire statements express wanting to change, Ability statements express capacity to change, Reasons statements explain why change is important, Need statements express necessity of change, and Commitment statements indicate intention to take action. The interviewer's goal is to elicit and reinforce change talk while not amplifying sustain talk, the patient's arguments for maintaining the status quo.

<image>Panel A illustrates the stages of change as a cyclical diagram: precontemplation (not considering change) → contemplation (ambivalent, weighing options) → preparation (planning to change) → action (actively changing) → maintenance (sustained change), with relapse as a common transition back to earlier stages rather than failure. Panel B presents the core principles of motivational interviewing: expressing empathy (reflective listening icon), developing discrepancy (gap between current behavior and goals), rolling with resistance (flexible arrows avoiding confrontation), supporting self-efficacy (building confidence). Panel C displays the OARS technique: Open-ended questions (exploration), Affirmations (acknowledging strengths), Reflections (mirroring and deepening), Summarizing (pulling together themes). Panel D shows change talk categories (DARN-C): Desire ("I want to..."), Ability ("I could..."), Reasons ("because..."), Need ("I need to..."), Commitment ("I will..."), with note about eliciting change talk while minimizing sustain talk.</image>

X. Special Considerations in Substance Use Disorders

Dual diagnosis, the co-occurrence of substance use disorder with another mental illness, is the rule rather than the exception. Integrated treatment addressing both conditions simultaneously produces better outcomes than sequential or parallel treatment. Common pairings include depression with alcohol use disorder, PTSD with opioid use disorder, and ADHD with stimulant use disorder. Each condition can worsen the other, creating a vicious cycle that responds best to coordinated intervention addressing both.

Several screening tools facilitate identification of substance use problems in clinical settings. The CAGE questionnaire uses four questions about Cutting down, Annoyance at criticism, Guilt about drinking, and using Eye-openers for alcohol screening. The AUDIT (Alcohol Use Disorders Identification Test) provides a more comprehensive ten-item assessment. The DAST (Drug Abuse Screening Test) screens for drug problems. The NIDA Quick Screen uses a single question about past-year substance use as an initial screen.

SBIRT (Screening, Brief Intervention, and Referral to Treatment) provides a public health approach to addressing substance use in healthcare settings. Screening uses validated tools to identify individuals at risk. Brief intervention consists of a short motivational conversation about reducing use for those with at-risk or problematic use. Referral to treatment connects individuals with more severe problems to specialized addiction treatment services. SBIRT has demonstrated effectiveness in reducing at-risk drinking when implemented in primary care and emergency department settings.

Harm reduction strategies aim to decrease the negative consequences of substance use for individuals not ready or able to achieve abstinence. Needle exchange programs reduce transmission of HIV and hepatitis among people who inject drugs. Naloxone distribution programs have saved thousands of lives by providing overdose reversal capability to users, families, and first responders. Safe consumption sites, where they exist, provide supervised environments for drug use with medical staff available to intervene. Medication-assisted treatment itself represents harm reduction by replacing illicit opioid use with prescribed medication.

<image>Panel A displays dual diagnosis concepts: integrated treatment superiority over sequential or parallel approaches, common pairings (depression/alcohol, PTSD/opioids, ADHD/stimulants), and the vicious cycle of mutual exacerbation requiring coordinated intervention. Panel B presents screening tools: CAGE questions (Cut, Annoyed, Guilty, Eye-opener), AUDIT (10-item comprehensive), DAST (drug screening), NIDA Quick Screen (single question initial screen). Panel C illustrates the SBIRT model as a flow: Screening (validated tools) → identification of risk level → Brief Intervention (motivational conversation for at-risk use) → Referral to Treatment (for severe problems). Panel D shows harm reduction strategies: needle exchange (HIV/HCV prevention), naloxone distribution (overdose reversal), safe consumption sites (supervised use with medical staff), MAT as harm reduction (replacing illicit use with prescribed medication).</image>

Summary

• Substance use disorder diagnosis uses eleven criteria organized into four clusters (impaired control, social impairment, risky use, pharmacological); severity is mild (2-3), moderate (4-5), or severe (6+)
• Addiction neurobiology involves the mesolimbic dopamine system; drugs produce massive dopamine release that overwhelms normal reward learning
• Alcohol withdrawal follows a predictable timeline and can be life-threatening; benzodiazepines are first-line treatment; thiamine prevents Wernicke encephalopathy
• Medications for alcohol use disorder include naltrexone (reduces craving), acamprosate (maintains abstinence), and disulfiram (aversive reaction)
• Opioid intoxication causes CNS and respiratory depression with miosis; naloxone reverses overdose
• Medications for opioid use disorder include buprenorphine (partial agonist, office-based), methadone (full agonist, OTP setting), and naltrexone (antagonist, requires opioid-free state)
• No FDA-approved medications exist for stimulant use disorder; psychosocial treatments are primary
• Tobacco cessation pharmacotherapy includes nicotine replacement, varenicline (most effective single agent), and bupropion
• Motivational interviewing uses OARS techniques (Open questions, Affirmations, Reflections, Summaries) to enhance motivation through the stages of change
• Harm reduction strategies including needle exchange, naloxone distribution, and MAT reduce negative consequences of substance use

Key Terms

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