Why Is Alcohol Addictive? The Physical and Psychological Factors and Treatments

Alcohol becomes addictive due to its profound effects on the brain and body, making it difficult for individuals to break free from its grip. Alcohol addiction, also known as alcohol use disorder, is a chronic condition characterized by an inability to control drinking despite negative consequences. About 33.1% of individuals aged 12 to 20, equating to 12.6 million people, reported having tried alcohol at least once in their lifetime, according to the 2023 National Survey on Drug Use and Health (NSDUH).

Alcohol is addictive because it alters brain chemistry, particularly affecting the reward and pleasure centers. It increases dopamine levels, a neurotransmitter linked to feelings of happiness and satisfaction. Repeated alcohol use rewires the brain to associate drinking with pleasure, reinforcing the habit. Over time, the brain adapts by reducing its natural dopamine production, precipitating tolerance. This means individuals need more alcohol to achieve the same pleasurable effects, which deepens addiction. Approximately 8.6% of individuals aged 12 to 20, representing 3.3 million people, reported engaging in binge drinking during the past month, as recorded in the National Survey on Drug Use and Health (2023).

The main reasons for alcohol addiction are altered brain chemistry, specifically in regions responsible for reward and decision-making, and alcohol provides temporary relief from emotional distress, creating a cycle of reliance that is difficult to escape.  This breeds compulsive drinking behaviors that spawn binge drinking patterns, defined by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) as a level of alcohol drinking that elevates blood alcohol concentration (BAC) to 0.08%—equivalent to 0.08 grams (0.0028 oz.) of alcohol per deciliter or higher. This typically occurs when a woman consumes four or more drinks, or a man consumes five or more drinks, within approximately two hours.

Treating alcohol addiction involves medications such as naltrexone or acamprosate to cut cravings and manage withdrawal symptoms, behavioral therapies like Cognitive Behavioral Therapy (CBT) tackle the underlying emotional triggers of addiction, while support groups such as Alcoholics Anonymous (AA) offer peer support and accountability. Detoxification under medical supervision is the first step, followed by long-term counseling and lifestyle changes to maintain sobriety.

With the right treatment plan, individuals overcome alcohol addiction and regain control of their lives. Roughly 70% of individuals with alcohol use disorder (AUD) and alcohol-related problems experience improvement through natural recovery, without the need for interventions. In contrast, fewer than 25% seek alcohol-focused services, as outlined by Tucker et al. 2020 in “Epidemiology of Recovery From Alcohol Use Disorder.”

What Are the Physical Factors That Make Alcohol Addictive?

The physical factors that make alcohol addictive are the release of dopamine, changes in neurotransmitter levels, building tolerance, triggering withdrawal symptoms, and altering brain structure. Alcohol alters neurotransmitter activity, builds tolerance, triggers withdrawal symptoms, and even changes brain structures, all of which induce the development and maintenance of alcohol addiction. These physical factors are essential for creating effective treatment strategies.

The physical factors that make alcohol addictive are listed below:

• Releasing Dopamine
• Changing Neurotransmitters
• Building Tolerance
• Triggering Withdrawal
• Altering Brain Structure

Releasing Dopamine

Dopamine is a neurotransmitter in the brain’s reward system. When a person consumes alcohol, it triggers the release of dopamine, furnishing a sense of pleasure or euphoria. This rewarding feeling reinforces the behavior, making the person want to drink again to experience the same sensation. In time, this generates a cycle where the individual becomes dependent on alcohol to feel pleasure, as the brain’s reward system becomes altered.

Chronic alcohol use initially increases dopamine (DA) transmission, promoting reward, but prolonged exposure leads to changes in the dopamine system. While chronic users function somewhat normally while drinking, alcohol withdrawal results in anhedonia (the inability to experience pleasure), aversion, and minimized reward processing. These symptoms are linked to a hypodopaminergic state (low dopamine levels) in areas like the cortex and nucleus accumbens, as cited by Trantham-Davidson H. & Chandler L. 2016 in “Alcohol-induced Alterations in Dopamine Modulation of Prefrontal Activity.”

Changing Neurotransmitters

Alcohol drinking affects several neurotransmitters in the brain, including gamma-aminobutyric acid (GABA) and glutamate. GABA is an inhibitory neurotransmitter that slows down brain activity, creating a calming effect, while glutamate is an excitatory neurotransmitter that increases brain activity. GABA is found in 25-50% of all synapses in the central nervous system (CNS), and its concentration in the healthy human brain remains relatively stable, as noted by Shyu et al. 2022 in their review, “Quantifying GABA in Addiction: A Review of Proton Magnetic Resonance Spectroscopy Studies.”

Alcohol intensifies GABA’s effects and inhibits glutamate, resulting in sedation and relaxation. As the brain adapts to alcohol, the balance of these neurotransmitters becomes commuted, making it harder for an individual to function without alcohol.

Building Tolerance

With repeated alcohol drinking, the brain and body become accustomed to its effects, instigating tolerance. This means that a person needs to consume larger quantities of alcohol to achieve the same effects. Tolerance escalates quickly, accelerating the risk of alcohol dependence as individuals continue to drink more in search of the desired effects. To help assess and address the development of tolerance and alcohol dependence, tools like the Alcohol, Smoking, and Substance Involvement Screening Test (ASSIST) are used to identify patterns of substance use and guide appropriate intervention strategies. ASSIST demonstrates 90% accuracy in identifying individuals at risk for substance use problems across diverse populations, as recounted by World Health Organization (WHO) research data.

Triggering Withdrawal

When someone dependent on alcohol stops drinking or cuts their intake, they experience withdrawal symptoms. These consist of anxiety, tremors, sweating, nausea, and in severe cases, seizures or delirium tremens (DTs). The body’s dependence on alcohol becomes evident through these withdrawal symptoms, reinforcing the cycle of addiction as individuals drink to avoid the discomfort of withdrawal. For instance, a study of individuals in outpatient substance abuse treatment revealed that 46% of those with an alcohol use disorder (AUD) also met the criteria for generalized anxiety disorder (GAD), with GAD preceding the onset of AUD by an average of 12.5 years in 67% of cases, as described by Smith J. & Book S. 2011 in “Comorbidity of Generalized Anxiety Disorder and Alcohol Use Disorders among Individuals Seeking Outpatient Substance Abuse Treatment.”

Altering Brain Structure

Chronic alcohol use sets structural changes in the brain. Prolonged drinking shrinks brain regions involved in memory, decision-making, and emotional regulation, such as the hippocampus and prefrontal cortex. These changes impair cognitive function and increase the difficulty of quitting alcohol, as the brain no longer functions in the same way as it did before the addiction.

The brains of individuals with alcohol dependence are 3–9% smaller than those of healthy individuals, with shrinkage occurring in areas such as the hippocampus, putamen, pallidum, thalamus, corpus callosum, and cerebellar gray matter. This drop in brain volume is strongly associated with the amount of alcohol consumed, as detailed by Daviet et al. 2022 in “Associations Between Alcohol Consumption and Gray and White Matter Volumes in the UK Biobank.”

What Are the Psychological Factors That Make Alcohol Addictive?

The psychological factors that make alcohol addictive are reducing stress, managing anxiety and depression, escaping emotions, reinforcing habits, and regulating trauma. These factors involve emotional and mental health issues that drive individuals to use alcohol as a coping mechanism. As time unfolds, alcohol use becomes a way to manage these issues, creating a cycle of addiction that is difficult to break.

The psychological factors that make alcohol addictive are listed below:

• Reducing Stress
• Managing Anxiety and Depression
• Escaping Emotions
• Reinforcing Habits
• Regulating Trauma

Reducing Stress

Alcohol is used as a way to cope with stress. The calming effects of alcohol temporarily diminish feelings of tension, anxiety, and pressure. For individuals dealing with high-stress environments or personal challenges, alcohol seems like a solution to unwind and relax. Gradually, this coping mechanism becomes entrenched, and the individual finds it harder to handle stress without drinking.

Dr. Ahmed Tawakol’s study at Massachusetts General Hospital as featured in CNNHealth’s (2023) “Small Amounts of Alcohol May Turn Down Stress in the Brain, Benefiting the Heart, New Study Finds” established that light to moderate drinking (1–14 drinks per week) lowered cardiac event risks by 20%, rising to 40% for those with anxiety, due to declining stress responses in the amygdala. Moreover, the study highlighted increased cancer risks at all alcohol levels, suggesting alternatives like exercise or meditation. Experts cautioned that the findings show correlation, not causation.

Managing Anxiety and Depression

Alcohol is utilized to self-medicate anxiety and depression. While alcohol serves temporary relief from these mental health conditions, it ultimately worsens them in the long run. Alcohol disrupts the balance of neurotransmitters in mood regulation, making anxiety and depression more pronounced. This produces a vicious cycle where individuals drink to relieve their symptoms but end up feeling worse, which provokes them to drink even more.

The National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), which has been conducted since 2001 to assess drinking behaviors and co-occurring conditions in the U.S., concluded that individuals with alcohol use disorder (AUD) are 3.7 times more likely to develop major depressive disorder than those without AUD, as reported by the University at Buffalo’s Clinical and Research Institute on Addictions (2016) in “Alcohol and Depression.”

Escaping Emotions

Many people turn to alcohol to escape difficult or overwhelming emotions, such as sadness, grief, or anger. Drinking numbs emotional pain, granting an ephemeral sense of relief. This emotional escape only delays dealing with underlying issues, making alcohol use a destructive way of faring that ultimately reinforces the need for alcohol.

This tendency to use alcohol as an emotional escape is often linked to underlying psychiatric conditions, which further complicate the relationship between alcohol use and mental health. Alcohol disrupts brain chemistry, contributing to erratic mood swings that can become particularly intense during withdrawal, leading to increased irritability and emotional instability. Two epidemiological studies, which conducted diagnostic interview surveys in representative community samples to examine the prevalence of psychiatric and substance use disorders, provide significant insights. The National Institute of Mental Health Epidemiologic Catchment Area (ECA) Study revealed that 16.5% of individuals with lifetime major depression also had an alcohol use disorder, as referenced by Quello et al. 2005 in “Mood Disorders and Substance Use Disorder: A Complex Comorbidity.”

Reinforcing Habits

For some, alcohol drinking becomes a deeply ingrained habit that is reinforced through repetition. Drinking in social settings, after work, or as part of a routine derives a habitual pattern. These habits become automatic over a long time, making it challenging for individuals to extricate themselves from the cycle of alcohol use.

The study “Bad Habits–Good Goals? Meta-analysis and Translation of the Habit Construct to Alcoholism” by Giannone et al. 2024 published in Nature, examines the interplay between habitual and goal-directed behaviors in alcohol use disorder (AUD). It challenges the strict habit-goal dichotomy, showing that these systems interact more subtly. Through a meta-analysis of animal studies and a review of human research, the authors spotlight how chronic alcohol exposure alters decision-making, prompting compulsive behavior. The study puts forth that both habitual and goal-directed behaviors settle addiction, with external factors like stress influencing this balance.

Regulating Trauma

Alcohol is sometimes used to manage the effects of trauma, including post-traumatic stress disorder (PTSD). For individuals with unresolved trauma, alcohol serves as a way to dull the emotional pain associated with traumatic experiences. While alcohol does confer temporary relief, it only exacerbates the symptoms of PTSD and prevents healing, making addiction more likely.

Symptoms of alcohol use disorders were reported by 46% of men and 1% of women, highlighting alcohol’s role in moderating trauma’s impact on mental health in post-conflict Uganda. Men with more alcohol-related issues showed less increase in PTSD and depression symptoms despite higher trauma exposure, consistent with the self-medication hypothesis, according to the study “Drinking to Ease the Burden: A Cross-sectional Study on Trauma, Alcohol Abuse and Psychopathology in a Post-conflict Context” by Ertl et al. 2016.

What Are the Effects of Alcohol Addiction?

The effects of alcohol addiction are liver damage, cardiovascular problems, neurological impairment, mental health issues, addiction and dependency, weakened immune system, and gastrointestinal issues. The longer someone is addicted to alcohol, the more profound these effects become, affecting their health and well-being.

The effects of alcohol addiction are given below:

• Liver damage: Chronic alcohol abuse causes fatty liver, alcoholic hepatitis, and cirrhosis. Over time, the liver’s ability to detoxify the body is impaired. This results in liver failure if untreated. Between 60% and 90% of individuals who consume over 60 grams (2.11 ounces) of alcohol daily develop hepatic steatosis. Of those with alcoholic steatosis who continue drinking, less than 50% progress to fibrosis, and only 10%–20% eventually develop cirrhosis, according to Torruellas et al. 2014 in the World Journal of Gastroenterology.
• Cardiovascular problems: Alcohol elevates blood pressure, evoking hypertension. It also contributes to heart disease, arrhythmias, and a higher risk of stroke. Chronic use weakens the heart muscle, causing cardiomyopathy. 

Alcohol abuse substantially surges the risk of atrial fibrillation (Hazard Ration (HR) 2.14 or 114%), myocardial infarction (HR 1.45 or 45%), and congestive heart failure (HR 2.34 or 134%), comparable to other established risk factors, as proposed in “Alcohol Abuse and Cardiac Disease” by Whitman et al. 2018 published in the Journal of the American College of Cardiology. The longitudinal analysis of 14,727,591 California residents revealed that 1.8% had alcohol abuse, with individuals lacking conventional cardiovascular risk factors showing a disproportionately higher susceptibility. These findings accentuate alcohol abuse as a modifiable risk factor with the potential to shrink the burden of cardiovascular disease.

• Neurological impairment: Long-term drinking causes brain shrinkage, cognitive decline, and memory loss. It impairs neurotransmitter function, affecting decision-making and emotional regulation. Chronic alcohol use also elicits peripheral neuropathy.

Cognitive impairments in alcohol-dependent individuals, in the absence of other neurological complications, are receiving more attention from addiction medicine professionals due to their influence on treatment. Studies have shown that between 50% and 80% of these patients experience compromised cognitive function, as noted by Bernardin et al. 2014 in “Cognitive Impairments in Alcohol-Dependent Subjects.”

• Mental health issues: Alcohol addiction is linked to depression, anxiety, and other mood disorders. It disrupts brain chemistry, exacerbating these conditions. Additionally, it provokes aggravated feelings of isolation and hopelessness. A Finnish study found that around 4% of individuals with alcohol use disorder (AUD) experience alcohol-induced psychosis, with 95% of these cases involving hallucinations and 51% involving delusions, as reported by Perälä et al. (2010) in “Alcohol-induced Psychotic Disorder and Delirium in the General Population.”
• Addiction and dependency: Continued alcohol use engenders physical and psychological dependence. Cravings and tolerance develop, and individuals struggle to quit even when facing negative consequences. Withdrawal symptoms are severe.

In the United States, 68% of males and 64% of females drink alcohol each year, with males drinking nearly three times as much (19.0 liters vs. 6.7 liters). Males also have higher rates of DUI arrests, alcohol-related hospitalizations, and alcohol-related deaths. Annually, 7% of males and 4% of females are diagnosed with alcohol use disorder (AUD), with 9% of both genders receiving treatment. Women are more likely to experience harm from others’ drinking, with 4.2% affected by a spouse and 5.6% by a family member, relative to 1.8% and 3.7% in men, as reported by White (2020) in “Gender Differences in the Epidemiology of Alcohol Use and Related Harms in the United States.”

• Weakened immune system: Alcohol suppresses the immune system, limiting the body’s ability to fight off infections. Chronic drinking expands susceptibility to pneumonia, tuberculosis, and other infections. Research emphasizes an important association between alcohol drinking and breast cancer, with even one drink per day increasing a woman’s risk by 5% to 15% compared to women who abstain from alcohol, as mentioned by the National Institute on Alcohol Abuse and Alcoholism in “Alcohol’s Effects on Health: Research-based Information on Drinking and Its Impact.”
• Gastrointestinal issues: Alcohol damages the digestive system, generating conditions like gastritis, ulcers, and pancreatitis. It impedes nutrient absorption and gives rise to malnutrition, further complicating health problems. An estimated 50% of alcoholics in the early stages of liver damage (such as fatty liver) and 30% to 80% of patients with advanced alcohol-induced liver injury (such as alcoholic hepatitis) report symptoms of abdominal discomfort, as advanced by Bode et al. 1992 in “Nutrition and Alcohol.”

What Are the Treatments for Alcohol Addiction?

The primary treatments for alcohol addiction are Medication-Assisted Treatment (MAT), behavioral therapies, residential treatment, outpatient treatment, and support groups. These approaches work together to help individuals overcome their addiction, address underlying psychological issues, and provide ongoing support for long-term recovery. Effective treatment is an amalgamation of medication, behavioral therapy, and support groups. These treatments are for individuals to manage withdrawal symptoms, alter harmful drinking behaviors, and rebuild their lives more healthily.

The common treatments for alcohol addiction are discussed below:

Medication-Assisted Treatment

Medication-assisted treatment (MAT) involves using medications to help individuals reduce alcohol cravings and prevent relapse. Medications such as disulfiram, acamprosate, and naltrexone can help people maintain sobriety by blocking the rewarding effects of alcohol or causing unpleasant side effects when alcohol is consumed. MAT is used in league with counseling and therapy to provide a comprehensive treatment approach.

A systematic review and meta-analysis of 118 clinical trials involving 20,976 participants demonstrated that pharmacotherapies such as 50 mg/day oral naltrexone and acamprosate significantly improved alcohol drinking-related outcomes compared to placebo. Notably, oral naltrexone (50 mg/day) reduced the rates of heavy drinking relapse, with a number needed to treat 11, as shown by McPheeters et al. 2023 in “Pharmacotherapy for Alcohol Use Disorder: A Systematic Review and Meta-Analysis.”

Behavioral Therapies

Behavioral therapies, such as Cognitive Behavioral Therapy (CBT), are important for treating alcohol addiction. These therapies help individuals identify and change negative thought patterns and behaviors associated with alcohol use. Behavioral therapies support long-term recovery for individuals to develop healthier coping strategies. by addressing the psychological aspects of addiction.

A survey of U.S. treatment facilities found that 96% of program administrators employ relapse prevention techniques, and 94% utilize Cognitive Behavioral Therapy (CBT), making it the second most common approach after “drug counseling.” This data, reported by the Substance Abuse and Mental Health Services Administration (2020) in the “National Survey of Substance Abuse Treatment Services (N-SSATS): 2020, Data on Substance Abuse Treatment Facilities,” accents the near-universal integration of CBT in treating alcohol and other drug (AOD) addictions within the modern treatment landscape.

Residential Treatment

Residential treatment programs provide intensive support for individuals struggling with alcohol addiction. These programs consist of living in a treatment facility for an extended period, where individuals receive round-the-clock care and participate in therapy, counseling, and support groups. Residential treatment is ideal for individuals with severe alcohol addiction or those who have not responded to other forms of treatment.

Rehabilitation programs for alcohol use disorder yield promising outcomes. One year post-treatment, 25% of clients maintained continuous abstinence, and 10% drank moderately without complications. Mortality rates remained below 2%, while non-abstinent clients achieved significant progress: abstaining three out of four days, reducing alcohol drinking by 87%, and experiencing a 60% decline in alcohol-related problems. These findings underscore that two-thirds of clients achieve notable improvement even without complete abstinence, as detailed in Miller et al.’s 2001 study, “How Effective is Alcoholism Treatment in the United States?”

Outpatient Treatment

Outpatient treatment programs allow individuals to receive treatment while living at home and continuing their daily activities. These programs encompass regular therapy sessions, support groups, and counseling. Outpatient treatment is effective for individuals with mild to moderate alcohol addiction who do not require 24-hour care. Success rates for outpatient alcohol treatment programs vary between 50% and 60%, influenced by factors such as treatment duration, aftercare support, and family involvement, according to the United Recovery Project.

Support Groups

Support groups, such as Alcoholics Anonymous (AA), provide a source of support for individuals in recovery. These groups offer a sense of community, shared experiences, and accountability, which can help individuals stay sober and maintain long-term recovery. For individuals who stay in AA for over 90 days, 56% continue attending meetings until the end of the year, as emphasized in the 2008 study “Alcoholics Anonymous Recovery Outcome Rates: Contemporary Myth and Misinterpretation,” referenced by 12steps.com.

How to Overcome Alcohol Addiction?

To overcome alcohol addiction requires a multifaceted approach involving determination, professional support, and lifestyle adjustments. Seeking therapy, enrolling in treatment programs, and building a supportive network are key steps. Avoiding alcoholic dementia necessitates maintaining a balanced diet, staying hydrated, and seeking timely medical care. Adopting preventive measures mitigates the long-term cognitive effects of alcohol abuse.

The common tips and strategies to assist in overcoming alcohol addiction and avoiding alcoholic dementia are listed below:

• Set clear, achievable goals: Outline specific objectives for cutting alcohol intake, such as setting limits or scheduling alcohol-free days, to maintain focus and measure progress.
• Seek therapy: Cognitive Behavioral Therapy identifies and addresses triggers, teaching coping mechanisms and strategies to prevent relapse and manage cravings effectively. Cognitive Behavioral Therapy (CBT) has proven to reduce substance use and support long-term recovery in 50–75% of cases, establishing itself as a cornerstone in addiction treatment programs, according to a large-scale study by Pybis J. et al. 2017.
• Enroll in Medication-Assisted Treatment: Medications like naltrexone or acamprosate, combined with counseling, chop cravings and withdrawal symptoms, boost recovery outcomes.
• Maintain a healthy diet: A balanced diet rich in vitamins, particularly thiamine, supports brain health, prevents deficiencies, and lowers the risk of alcoholic dementia.

A study analyzing thiamine supplementation among 14,998 ICU patients with alcohol use disorder (AUD) from 2010 to 2017 revealed that 51% received supplementation. The rates varied by condition: 59% for alcohol withdrawal, 26% for septic shock, 41% for traumatic brain injury (TBI), and 24% for diabetic ketoacidosis (DKA). Over half (52%) received thiamine within 12 hours, predominantly via enteral routes (41%), exposing a care gap for AUD patients with conditions beyond alcohol withdrawal, as analyzed in “Thiamine Supplementation in Patients with Alcohol Use Disorder Presenting with Acute Critical Illness” by Pawar et al. 2021.

• Avoid binge drinking: Limiting alcohol to moderate levels and refraining from episodes of heavy drinking minimizes damage to the brain and overall health. The National Institute on Alcohol Abuse and Alcoholism (NIAAA) defines binge drinking as a drinking pattern that elevates blood alcohol concentration (BAC) to 0.08%—equivalent to 0.08 grams (0.0028 oz.) of alcohol per deciliter or higher. This occurs when a woman consumes four or more drinks, or a man consumes five or more drinks, within approximately two hours.
• Join support groups: Programs like Alcoholics Anonymous offer peer support, shared experiences, and accountability, fostering a sense of belonging and motivation to stay sober. The effectiveness of 12-step programs ranges from 5–12% to 49%, with varying success rates. A study highlighted by Erickson M. 2020 in the Stanford Medicine publication “Alcoholics Anonymous Most Effective Path to Alcohol Abstinence” deduced the program to be 60% more effective in certain cases. While 12-step programs excel in providing peer-driven support, they lack the individualized therapeutic approaches offered by cognitive-behavioral therapy (CBT) and medication-assisted treatment (MAT).
• Engage in regular physical activity: Exercise promotes mental clarity, reduces stress, and supports overall recovery by improving physical health and resilience.

How Much Time Does It Take to Overcome Alcohol Addiction?

The time it takes to overcome alcohol addiction is 10 days in terms of detoxification. Surmounting alcohol addiction differs greatly depending on aspects such as the severity of the addiction, the individual’s health, and their commitment to treatment. On average, it takes several months to a year to achieve sobriety and establish a healthy, alcohol-free lifestyle. Relapse is common, and the process is longer for some individuals.

Seventy-nine percent of home detox patients and 78% of day hospital patients successfully completed detoxification within 10 days. At the 60-day follow-up, 45% of home detox patients and 31% of day hospital patients reported tremendous improvements in alcohol-related issues. These improved outcomes were linked to continued treatment attendance, highlighting that both home and day hospital detox are viable and effective alternatives to inpatient detox for selected patients, as explored by Allan et al. 2000 in “Detoxification From Alcohol: A Comparison of Home Detoxification and Hospital-Based Day Patient Care.”

Can We Use Family Therapy for Alcohol Addiction?

Yes, you can use family therapy for alcohol addiction. Family therapy is an effective part of alcohol addiction treatment. Family members play a critical role in an individual’s recovery process by providing emotional support and helping to rebuild relationships damaged by alcohol use. Family therapy steers family dynamics, bolsters communication, and guides the individual and their loved ones in the recovery process. In the Harvard Counseling for Alcoholics’ Marriages Project, over 50% of husbands with alcohol use disorders who participated in couples counseling remained alcohol-free during the first year after treatment.