Alcohol and Drugs: Health Effects

A drug can be:

  • A natural or synthetic substance used in the diagnosis, treatment or prevention of a disease, or to relieve pain
  • A substance that produces a state of arousal, contentment, euphoria, or sleep-inducing properties
  • Addictive or habit-forming when used continuously or excessively, with possible withdrawal symptoms when drug use is stopped
  • Legal or illegal (little to do with its potential for addiction or harm)

How Drugs Affect the Brain

When someone puts drugs into their body, they tap into the brain’s communication system and tamper with the way nerve cells normally send, receive and process information.

Different drugs work differently because of their chemical structures. There are at least two ways drugs work in the brain. Some imitate the brain’s natural chemical messengers. Others over-stimulate the “reward circuit” of the brain by flooding it with dopamine, a neurotransmitter that is present in parts of the brain that regulate feelings of pleasure.

Drug use can lead to the release of such large quantities of dopamine that other activities no longer feel pleasurable. A person may feel flat, lifeless and depressed, and may be unable to enjoy things that once felt good or made them happy. The person may need drugs just to bring dopamine levels up to normal.

Problematic Drug Use

People use alcohol and other drugs for a variety of reasons, some of which may be informed by their social and cultural experiences. Some people may use substances sporadically or without harm. However, for others, continued substance can lead to harmful consequences. The harms associated with drug use vary and are based on several factors. Potential harms include:

  • Physical harms: HIV, hepatitis C, non-fatal or fatal overdose, wounds, withdrawal, violence
  • Psychological harms: depression, isolation, stigma, psychosis
  • Social harms: relationship issues, isolation from community, stigma
  • Economic harms: loss of money, loss of job, loss of housing
  • Legal harms: incarceration, criminal record

Substance Use Disorders (SUD)

Substance use disorders (sometimes called addiction or dependence) are chronic, often relapsing conditions that cause people to continue using alcohol or drugs despite negative results. While initiating drug use is usually a conscious choice, changes to the brain associated with substance use can limit a person’s self-control and can strengthen the urge to use drugs.

Substance use disorders can be treated with a combination of therapy and medications. Treatment works best when it is tailored to the individual and takes into account not only drug use, but other social, emotional and health issues. Like other chronic diseases, people with substance use disorder can return to use. Relapse is not a sign of treatment failure but of the need to adjust and provide additional support. For more information on treatment, visit Treatment for Opioid Use Disorders.


Recent studies have indicated increases in alcohol use and related mortality. Learn more about alcohol and how to reduce associated health risks at the Alcohol page.


Cannabis use is legal for people over 21 in New York. Learn more about cannabis and its effects at the Cannabis page.


Fentanyl is a powerful synthetic opioid increasingly found throughout the NYC drug supply. Learn more at the Fentanyl page.

Drug Profiles

Information about some of the most talked-about substances has been compiled from multiple references. They are included here to provide you with the facts about what these drugs are and what they do.

Additional Resources

More Information