Causes, Symptoms & Effects of Drug Addiction

Cedar Crest Hospital & Residential Treatment Center helps individuals who are struggling with drug addiction find long-term recovery. Located in Belton, TX, Cedar Crest is the leader in mental health care.

Understanding Drug Abuse & Addiction

Learn about drug abuse

Substance abuse, or drug abuse, is defined as a pattern of use of psychoactive substances in amounts or manners that are harmful to the user and/or others. A prolonged period of drug abuse of can cause dependence and addiction, which is associated with a variety of cognitive, behavioral, and physiological changes. These changes include strong drug cravings as well as a desire to continue using the drug despite any negative consequences. If a person does become addicted, the drug usage slowly becomes a higher priority than almost any other activity or obligation.

It can be hard to understand why some people become addicted to drugs.  It’s often erroneously assumed that people who abuse drugs lack the willpower to stop. The truth is that drug addiction is a complex brain disorder that requires lifelong treatment, not simply a strong desire to quit. Drug use changes the brain in manners that promote compulsive drug use, which makes quitting a challenge, even for people who really want to stop using. Recent advances have led to the understanding that drug addiction is a chronic, yet treatable condition that can successfully be overcome through appropriate support and management.

There are a wide variety of drugs that are commonly abused. These categories of drugs cause different effects and are often abused in different ways. The most common categories of drugs of abuse include:

Marijuana (“grass,” “pot,” and “weed”) is the most commonly abused drug in the United States. Pot can be smoked or swallowed and causes feelings of euphoria, impairs memory, impedes coordination, and distorts reality.

Narcotics and opiates, including heroin, prescription painkillers, and opium, can be injected, smoked, snorted, or swallowed. These drugs lead to feelings of euphoria and relaxation as well as a sense of well-being.

Stimulants, including cocaine (“coke”), amphetamine (“uppers”), and methamphetamine (“meth”), can be snorted, injected, smoked, and swallowed to produce feelings of increased energy and mental acuity.

Hallucinogens and dissociative drugs, also known as psychedelics, include PCP, LSD, peyote, ecstasy, ketamine, and psilocybin. These drugs cause changes in sensory and thought perceptions and can be swallowed, absorbed through oral mucosa, and smoked.

Inhalants, which includes solvents (such as gasoline and glues), aerosols (spray paint), gasses (propane, butane), nitrous oxide, and nitrates (“poppers”), are chemicals that cause intoxication when sniffed or inhaled (a process known as “huffing”).

CNS depressants and downers are drugs that slow down the central nervous system and include tranquilizers, barbiturates, benzodiazepines, GHB, and Rohypnol. These drugs cause relaxation and sedation.


Drug addiction statistics

Worldwide, at least 15.3 million people struggle with drug abuse. IV drug abuse (easily the most dangerous way to use illegal drugs) has been reported in 148 countries, of which 120 countries report increased amounts of HIV/AIDS infection among this population.

In the United States, illegal drug use is on the rise. In 2009, about 23.5 million people ages 12 and older in the U.S. (or 9.3% of the population) needed inpatient treatment for substance abuse or alcoholism. Of these, only about 2.6 million (or 11.2% of that population) people who needed inpatient treatment received it at a specialized treatment center.

Causes and Risk Factors

Causes and risk factors for drug addiction

There is not one single factor identified that can determine whether or not a person will become addicted to drugs. The causes for addiction involve the influence of a combination of factors working together. The more risk factors an individual has, the greater the chance they will develop an addiction.

Genetic: Our inborn genes combined with environmental influences account for approximately half of the vulnerability to addiction. Addiction tends to run in families; people who have a first-degree relative who has struggled with addiction are more likely to develop an addiction.

Physical: Drugs contain certain chemicals that act on the body’s communication system and disturb the ways in which nerve cells normally send, receive, and process information. The longer a person abuses drugs, the more likely that the drugs will cause lasting damage to this system and lead to the body reducing the naturally-occurring communication signals of the brain (neurotransmitters), leading to a physical dependence upon drugs.

Environmental: People who begin to experiment with drugs at an earlier age are at an increased risk for developing an addiction to drugs later in life. Additionally, belonging to a peer group in which drug use is prevalent can lead an individual to experimentation with drugs, which may eventually lead to abuse and addiction. Others will find that effects from certain substances temporarily alleviate some of the unpleasant stresses associated with life and will become dependent on these substances as a way to cope with negative life events.

Risk Factors:

  • Lack of parental supervision and involvement
  • Lower socioeconomic status
  • Poor social and life skills
  • Availability of drugs
  • History of aggressive behaviors
  • History of physical or sexual abuse

Signs and Symptoms

Signs and symptoms of drug addiction

The symptoms of drug abuse will vary depending upon the substance abused, frequency of use, individual makeup, length of use, and presence of physical dependence. The symptoms of use of common drugs of abuse follow:


  • Euphoria and relaxation
  • Decreased ability to concentrate and learn
  • Anxiety and panic attacks
  • Psychosis
  • Cough
  • Impaired reaction time
  • Distorted sensory perception
  • Impairment in balance, coordination, and memory
  • Increased heart rate and appetite


  • Drowsiness and dizziness
  • Euphoria
  • Sensation of heaviness in extremities
  • Impaired memory and increased confusion
  • Syncope
  • Respiratory depression and arrested breathing


  • Tachycardia
  • Paranoia
  • Violent, erratic behaviors
  • Psychosis
  • Hypertension
  • Hyperthermia
  • Increased metabolism and decreased appetite
  • Feelings of exhilaration and increased energy
  • Increased mental acuity
  • Tremors
  • Irritability
  • Anxiety, panic attacks

Hallucinogenic and dissociative drugs:

  • Altered states of perception and total disorientation
  • Insomnia
  • Tremors
  • Impulsive behaviors
  • Nausea, vomiting, diarrhea
  • Panic attacks and increased anxiety
  • Increased heart rate, body temperature, and blood pressure


  • Impaired motor coordination
  • Loss of memory
  • Weakness and fatigue
  • Brief intoxication
  • Loss of inhibition
  • Nausea and vomiting
  • Syncope
  • Headache

Depressants and downers:

  • Confusion and disorientation
  • Slurred speech
  • Impaired coordination
  • Drowsiness and fatigue
  • Decreased respiration and heart rate
  • Depression
  • Impaired memory and judgment
  • Decreased anxiety
  • Overall feelings of relaxation and wellbeing
  • Lowered inhibitions


Effects of drug addiction

The long-term effects and complications of substance abuse will vary depending upon the type of substance abused, presence of other health-related conditions, frequency of use, individual genetic makeup, and length of drug abuse.

The most common effects of drugs of abuse are grouped by substance of abuse:


  • Frequent respiratory infections
  • Decline in mental health
  • Increased risks for cancer

Opiates and narcotic drugs:

  • Hypotension
  • Decreased respiration rate
  • Mood swings
  • Addiction
  • Collapsed veins
  • Septicemia
  • Abscess at injection site
  • Constipation
  • Endocarditis
  • Hepatitis B and C
  • HIV/AIDS infection
  • Fatal overdose
  • Coma
  • Death


  • Psychosis
  • Malnutrition
  • Insomnia
  • Cardiac and cardiovascular complications
  • Addiction
  • Nasal perforation
  • Severe dental problems (“meth mouth”)
  • Stroke
  • Heart attack
  • Seizures

Hallucinogenic and dissociative drugs:

  • Cardiac complications
  • Liver damage
  • Violent, erratic behaviors
  • Break with reality
  • Flashbacks
  • Intrusive thoughts
  • Consequences of impulsive, risky behaviors
  • Continuing hallucinations
  • Memory loss


  • Loss of consciousness
  • Memory impairment
  • Damage to cardiovascular and nervous system
  • Delusions
  • Confusion and disorientation
  • Coma
  • Seizures

CNS depressants and downers:

  • Addiction
  • Consequences of risk-taking behaviors
  • Amnesia
  • Hypotension
  • Decreased respiration rate
  • Tolerance
  • Withdrawal

Overdose & Withdrawal Effects

Effects of drug overdose & withdrawal

Each different substance can lead to the presence of unpleasant withdrawal symptoms if a person abruptly stops using or reduces the amount abused. Withdrawal symptoms range from mild to very severe depending on the type of drug; if not properly monitored, it can end in death.

Marijuana Withdrawal:

  • Anger
  • Loss of concentration
  • Headaches
  • Agitation
  • Mood swings
  • Insomnia
  • Depression
  • Nightmares, night sweats, and vivid dreams

Opiate Withdrawal:

  • Tremors and spasms
  • Anxiety and panic
  • Nausea, vomiting, diarrhea
  • Tachycardia
  • Irritability, agitation, restlessness
  • Insomnia
  • Chills and sweating
  • Goosebumps
  • Hypertension
  • Muscle and bone pain
  • Depression
  • Suicidal thoughts and behaviors

Opiate Overdose:

  • Miosis – constricted pupils
  • Decreased, erratic, sometimes absent respiration rate
  • Cyanosis
  • Pale, clammy skin
  • Slurred speech
  • CNS depression
  • Ventricular arrhythmias
  • Slowed, erratic, or stopped heart rate
  • Acute mental status change, decreased response to stimuli
  • Hypotension
  • Coma

Stimulant Withdrawal:

  • Drug cravings
  • Insomnia and fatigue
  • Nausea and vomiting
  • Agitation and irritability
  • Depression
  • Tremors and chills
  • Muscle pain
  • Psychosis

Stimulant Overdose:

  • Nausea and vomiting
  • Chills and profuse sweating
  • Tachycardia
  • Erratic breathing
  • Paralysis
  • Heart attack
  • Extreme anxiety, panic, agitation, aggression, restlessness
  • Passing out
  • Tightening in chest or chest pain
  • Hyperthermia
  • Hallucinations
  • Paranoia
  • Seizures
  • Stroke

Hallucinogenic and Dissociative Withdrawal:

  • Cravings
  • Fatigue
  • Irritability
  • Anhedonia
  • Suicide

Hallucinogenic and Dissociative Overdose:

  • Self-injury or suicide attempts
  • Tachycardia
  • Tachypnea
  • Agitation and anxiety
  • Acute psychotic behavior
  • Psychotic break
  • Hallucinations

Inhalant Withdrawal:

  • Syncope
  • Depression
  • Nausea and vomiting
  • Headache
  • Anxiety and irritability
  • Cravings for the drug

Inhalant Overdose:

  • Sudden heart failure
  • Hypoxia
  • Cardiac failure
  • Coma
  • Sudden sniffing death syndrome

CNS Depressants Withdrawal:

  • Loss of appetite
  • Tachycardia
  • Insomnia
  • Anxiety, agitation, and irritability
  • Headache
  • Seizures

CNS Depressants Overdose:

  • Ataxia, weakness and hypotonia
  • Paradoxical agitation
  • Respiratory depression
  • Dizziness
  • Anxiety and agitation
  • Confusion and drowsiness
  • Diplopia and nystagmus
  • Unresponsiveness
  • Hypotension
  • Increased risk of death when combined with alcohol
  • Amnesia
  • Coma

Co-Occurring Disorders

Drug addiction and co-occurring disorders

Many people who struggle with drug abuse and addiction have a co-occurring mental health disorder. Some of the most commonly co-occurring disorders include:

  • Depressive disorders
  • Anxiety disorders
  • Bipolar disorder
  • Schizophrenia
  • Polysubstance abuse
  • Antisocial personality disorder
  • Borderline personality disorder
  • Post-traumatic stress disorder (PTSD)
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I was struggling with addiction for many years. It was only with Cedar Crest that I was able to achieve lasting sobriety. 2 years and counting!

– Anonymous Patient
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