What is a Substance Use Disorder?

By Ben Egbers, DNP at Axis Integrated Mental Health

Substance Use Disorder (SUD) isn’t just “substance misuse”.

It’s a clinical diagnosis defined by the DSM-5-TR (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition) that involves changes in brain structure, behavior, and mental health.

As per the DSM‑5-TR, SUD is a chronic, recurrent brain disorder marked by impaired control over substance use, which could be: alcohol, nicotine, marijuana, prescription medications (e.g., benzodiazepines like Xanax; stimulants like Adderall), or “street drugs” like cocaine or heroin. 

It encompasses different phases, including:

• Active addiction 
• Substance intoxication, as well as
• Recovery

It is often accompanied by co-occurring mental health issues, commonly depression, anxiety, impairments in focus and executive function, and sleep and appetite disruption, among others.

This article helps you understand SUD and distills that expertise into a compassionate, practical roadmap. 

Understanding Substance Use Disorder (SUD)  

In clinical language, a person is diagnosed with SUD when the individual is unable to decrease or stop their substance use despite significant negative impacts on their functioning, including, but not limited to, job loss, family disruption, or negative physical or mental health effects.

It's more than misuse; it reflects a chronic, progressive brain disorder that affects judgment, impulse control, emotional regulation, and motivation. 

The DSM-5 outlines 11 diagnostic criteria for SUD. Let’s take a moment to explore these in greater detail. 

The 11 DSM-5 Criteria for SUD 

A diagnosis is based on the number of these criteria met in 12 months: 

• Using more of the substance than intended or for longer than intended.
• Unsuccessful efforts to cut down or control use.
• Spending a great deal of time obtaining, using, or recovering from the substance.
• Craving or a strong desire to use the substance.
• Recurrent use results in failure to fulfill major obligations at work, school, or home.
• Continued use despite persistent social or interpersonal problems caused by the substance.
• Giving up important social, occupational, or recreational activities because of use.
• Using substances in situations where it’s physically hazardous (e.g., driving).
• Continued use despite knowing it’s causing physical or psychological harm.
• Developing tolerance (needing more of the substance to the same effect).
• Experiencing withdrawal symptoms when not using the substance. 

Often, clinicians may classify a substance use disorder into mild, moderate, and severe, based on the number of criteria met by the patient: 

• Mild: 2–3 criteria 
• Moderate: 4–5 criteria
• Severe: 6 or more criteria 

Substance Use Disorder vs. Substance Abuse: What’s the Difference? 

While “substance abuse” is still commonly used in conversation, there are ongoing efforts to usher in updated language that is less stigmatizing.

In the case of illegal substances, the term “substance use” is preferred, and for prescription medications, “substance misuse” is the preferred terminology.

It’s also worth noting that just because someone engages in substance use/misuse, it does not necessarily mean that they are struggling with a formal substance use disorder. 

The table below highlights the key differences between these two terms and why the shift in language matters:  

Advanced Signs of SUD 

Physical (substance-dependent) 

• Bloodshot or glazed eyes 
• Sudden changes in weight or appetite
• Poor hygiene and grooming habits
• Unusual body odors (from chemicals or withdrawal)
• Frequent nosebleeds (from snorting drugs)
• Frequent yawning (common in opioid withdrawal)
• Profuse sweating not accounted for by room temperature or activity 

Behavioral  

• Lying or being secretive about whereabouts or activities 
• Declining work or academic performance
• Stealing or legal issues related to use
• Isolating from friends and family
• Neglecting responsibilities or erratic behavior 

Emotional and Psychological 

• Sudden mood swings or irritability 
• Anxiety, depression, or apathy
• Paranoia or hallucinations in severe cases
• Emotional numbness or flat affect (external expression of emotion)
• Hopelessness or suicidal ideation 

How Intoxication Affects Brain Function 

Substance intoxication doesn’t just alter mood; it reshapes brain function, sometimes permanently.

The brain’s reward circuitry, particularly the basal ganglia, is especially vulnerable to the brain’s reaction.

This system is designed to reinforce life-sustaining behaviors like eating, bonding, or exercising.  

Repeated use of substances can hijack this pathway, flooding it with various Using substances over and over can take over this pathway.

It fills it with different neurochemicals, like endorphins. Endorphins are the "feel-good" neurotransmitters.

They can create the euphoria people often feel when using substances.

This also leads to the release of dopamine.

Dopamine is a neurotransmitter that reinforces certain behaviors.

This reinforcement can lead to repeated actions, like using substances again.  

Neurological Impact of Intoxication 

• Overstimulation of Dopamine Pathways
  • Drugs like cocaine, opioids, nicotine, and alcohol stimulate dopamine release at 2–10 times the level of natural rewards.
  • This overwhelms the brain’s ability to regulate itself, causing intense euphoria and teaching the brain: “Do this again!” 
• Neuroadaptation and Tolerance
  • With repeated use, dopamine receptor sensitivity is reduced, requiring more of the substance to achieve the same high, a phenomenon known as tolerance.
  • At this stage, people using substances often increase doses or combine substances, which can increase the risk of overdose. 
• Disruption of Executive Function
  • Substances can cause alterations in the function of the prefrontal cortex, the region responsible for judgment, impulse control, and long-term planning.
  • This leads to impaired decision-making and prioritizing short-term relief (using) over long-term consequences (health, relationships). 
• Triggering of Craving and Withdrawal Cycles
  • While the basal ganglia adjusts to the pleasure of euphoria caused by the substance, another brain structure, the extended amygdala, an area associated with anxiety, irritability, and unease, becomes more sensitive, causing feelings of withdrawal in the absence of the substance.
  • At this point, sobriety feels emotionally and physically painful.
  • Even months into abstinence, cues (sights, smells, stress) can trigger cravings via the amygdala and hippocampus–regions linked to memory and emotion. 

Immediate vs Long-Term Effects of SUD 

Immediate Effects: Altered Perception, Reward, and Emotion 

Long-Term Effects: Cognitive, Emotional, and Social Deterioration 

With prolonged use, the brain undergoes structural and chemical changes that are psychologically debilitating. 

• Cognitive Decline: Long-term users often experience impaired memory, attention deficits, and slower reaction times. 
• Emotional Blunting and Mood Disorders: Chronic substance use reduces the brain’s natural production of dopamine and serotonin, leading to anhedonia, depression, and emotional numbness.
• Increased Risk of Psychiatric Disorders: Long-term use raises vulnerability to depression, anxiety, psychosis, among others, especially in genetically predisposed individuals.
• Social and Relational decline: As substance use becomes prioritized, users often isolate, experience relationship breakdowns, and suffer job or housing loss.
• Neuroplastic Damage: Neuroimaging studies show gray matter shrinkage in key decision-making and emotional regulation areas after years of substance misuse. These changes often reverse slowly, if at all, emphasizing the need for early intervention. 

Addiction Therapy: Types and Effectiveness 

1. Cognitive Behavioral Therapy (CBT): CBT teaches clients to identify unhelpful thought patterns and replace them with healthier cognitive strategies and behaviors.
2. Motivational Interviewing (MI): MI helps clients identify and resolve ambivalence and build motivation to change, especially effective in early-stage recovery.
3. Group and Family Therapy Approaches: Group therapy offers peer connection, while family therapy repairs damaged family dynamics and fosters mutual accountability.
4. Pharmacotherapy: Depending on the disorder, medication management may help the individual in their recovery process. 

The 5 Essential Stages of SUD Recovery 

1. Precontemplation (“Not Ready”) 
   1. Individuals do not yet recognize their substance use as problematic. They may minimize consequences or deny issues altogether.
   2. Clinically, our role is to explore and build awareness and plant seeds of change through gentle exploration, not confrontation
2. Contemplation (“Thinking About It”) 
   1. Here, clients express ambivalence. They acknowledge problems but haven’t committed to change.
   2. Therapy focuses on motivational interviewing, exploring the pros and cons of use vs. change, while validating uncertainty.
3. Preparation (“Getting Ready”) 
   1. Clients begin active planning: setting quit dates, removing triggers, researching treatment options, and beginning small behavior changes
   2. Providers assist by offering tailored tools: detox referrals, safety planning, and engaging support systems.*
4. Action (“Doing It”) 
   1. This stage involves visible change: entering treatment, stopping use, attending therapy, and building new routines 
   2. Clinically, professionals support clients with coping strategies, relapse prevention plans, medication-assisted therapies, and supportive community involvement. 
5. Maintenance (“Sustaining Recovery”) 
   1. Clients work on solidifying gains, preventing relapse, and integrating new behaviors long-term 
   2. Support takes the form of aftercare, alumni groups, family sessions, and ongoing therapy, treating recovery like a lifelong health journey. 

When to Seek Help or Treatment? 

Many people delay seeking help because they feel like they aren’t “bad enough.”

The truth is that early intervention can change the trajectory of the substance use disorder and the person’s life. 

Recognizing Crisis Points 

• You’ve recognized concern over your use patterns 
• You've tried to stop, but can't
• Your relationships are breaking down
• You use substances to feel “normal”
• Legal, financial, or health issues have escalated
• You feel like you’ve lost control 

FAQs About Substance Use Disorder (SUD) 

1. What’s the difference between substance use and substance use disorder? 
2. Can someone have SUD without using drugs or alcohol daily?
3. Is substance use disorder genetic?
4. How long does treatment usually last for SUD?
5. What types of therapy are most effective for drug or alcohol addiction?