Substance Use Disorder (SUD)

Substance use disorder represents one of the most significant public health challenges worldwide, affecting millions of individuals and families across all demographics, socioeconomic levels, and geographic regions. While this site focuses primarily on alcohol use disorder, understanding substance use disorder broadly provides important context about the nature of addiction, how different substances affect the brain and body, and the principles of effective treatment that apply across all substances.

Substance use disorder is a chronic medical condition characterized by compulsive substance use despite harmful consequences.^[1][2] It involves complex interactions between brain circuits, genetics, environment, and personal experiences.^[4] No single factor causes substance use disorder; rather, it develops through the interplay of biological vulnerability, psychological factors, social influences, and the specific effects of the substances used. Understanding substance use disorder as a medical condition rather than a moral failing or character flaw is essential for reducing stigma, accessing appropriate treatment, and supporting recovery.^[2]

Different substances produce addiction through varied mechanisms, though all share the common feature of disrupting the brain's reward system and other critical neural circuits. Alcohol, opioids, stimulants, benzodiazepines, and cannabis each have distinct effects on the body and brain, different patterns of use and consequences, varied withdrawal syndromes, and specific treatment approaches. Many individuals use multiple substances simultaneously or sequentially, a pattern called polysubstance use that complicates both the clinical picture and treatment approach.

This comprehensive guide examines substance use disorder across multiple substances, exploring how each class of drugs affects the body and brain, the signs and symptoms of problematic use, the specific risks and consequences associated with different substances, evidence-based treatment approaches, and the principles of recovery that apply regardless of the substance involved. While our primary focus remains alcohol use disorder, understanding the broader landscape of addiction provides valuable perspective on this complex medical condition.

What is Substance Use Disorder?

Substance Use Disorder (SUD) is a complex medical condition characterized by an inability to control substance use despite harmful consequences to physical health, mental wellbeing, relationships, work, and other life domains. SUD fundamentally affects brain circuits involved in reward, motivation, memory, decision-making, and self-control. It is a chronic, often relapsing disease that requires professional treatment—not a moral failing, character weakness, or lack of willpower.

The American Psychiatric Association's Diagnostic and Statistical Manual (DSM-5) defines SUD based on 11 criteria organized across four categories: impaired control over substance use, social impairment from use, risky use in dangerous situations, and pharmacological criteria including tolerance and withdrawal.^[1][5] The presence of two or three criteria indicates mild SUD, four or five indicates moderate SUD, and six or more indicates severe SUD. This dimensional approach recognizes that substance use disorder exists on a continuum of severity rather than as a binary present/absent condition.^[1]

Not everyone who uses substances develops substance use disorder. Multiple factors influence vulnerability including genetic predisposition (accounting for approximately 40-60% of risk), environmental factors such as trauma, stress, and substance availability, age of first use with earlier initiation increasing risk, co-occurring mental health conditions, and social influences including peer use and family dysfunction. The interplay of these factors determines individual risk, though no combination guarantees that someone will or will not develop SUD.

Common Substance Categories

Polysubstance Use

Polysubstance use involves using multiple substances concurrently or sequentially. This pattern significantly increases health risks, complicates treatment, and raises overdose risk dramatically. Common combinations include:

• Alcohol + Benzodiazepines — Both depress respiratory function; combination can be fatal
• Opioids + Benzodiazepines — Dramatically increases overdose risk; often involved in fatal overdoses
• Stimulants + Alcohol — Masks intoxication, leading to overconsumption and alcohol poisoning
• Stimulants + Opioids — "Speedball" combination; extremely dangerous for cardiovascular system

The Neuroscience of Addiction

Substance use disorder fundamentally alters brain structure and function. Key changes occur in:

Evidence-Based Treatment Principles

Effective SUD treatment follows established principles supported by decades of research:

• Addiction is a treatable disease affecting brain function and behavior
• No single treatment is right for everyone — care must be individualized
• Treatment must address multiple needs beyond substance use
• Remaining in treatment long enough is critical for lasting recovery
• Behavioral therapies are the cornerstone of effective treatment
• Medications are important for many especially opioid and alcohol use disorders
• Co-occurring disorders require integrated treatment addressing both SUD and mental health
• Medical detox is only the first step — ongoing treatment is essential
• Recovery is a long-term process requiring continued care and support

Getting Help for Substance Use Disorder

If you or a loved one struggles with substance use, help is available. Treatment works, recovery is possible, and you don't have to face this alone.

Frequently Asked Questions About Substance Use Disorder

Get Treatment Information

To find substance use disorder treatment facilities in your area, call our 24/7 helpline at (914) 594-5851. Our treatment specialists can help you find programs that address alcohol, drugs, or polysubstance use. For New York State residents, visit our NY Resources page for regional treatment options.

Learn More

• AUDIT Screening for Alcohol Use Disorder
• Evidence-Based Treatment Options
• Recovery and Relapse Prevention
• Treatment Options Overview
• Connect with Treatment Specialists