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How Cannabis Use Impacts Long-Term Health

The Effects and Dangers of THC

Cannabis, more commonly referred to as marijuana, is actually the umbrella term that refers to the plant that creates compounds called cannabinoids. (Marijuana is one type of cannabis plant.)

Whether you call it cannabis or marijuana, use is on the rise. Some people use it recreationally, while others use it for medicinal purposes to treat pain, nausea and sleep disorders. It can be smoked, inhaled, brewed as tea or consumed in edibles.

It’s also associated with many long-term, harmful effects. Two Northwestern Medicine experts share what you need to know about the impact of cannabis use.

How Cannabis Affects Your Body

Tetrahydrocannabinol (THC) is the chemical substance in cannabis that acts on specific parts of your brain. Whether ingested or smoked, THC causes the brain to release dopamine, a chemical that elicits the sensation of pleasure or relaxation. Yet, it can also cause mood changes, depression, suicidal thoughts, memory issues and even disrupted learning.

Once ingested, THC enters the bloodstream and into the brain, where it activates the hippocampus and orbitofrontal cortex. This can impact your ability to form new memories and impair your ability to process information.

Some immediate effects can include:

  • Bloodshot eyes
  • Increased heart rate
  • Increased blood pressure
  • Anxiety
  • Impaired memory
  • Changes in mood
  • Altered sense of time
  • Difficulty problem-solving
  • Hallucinations

“Basic cannabis intoxication involves inappropriate laughter, unsteady gait and red eyes. But higher-concentration THC products, including edibles and drops, can cause extreme effects,” says Patrick M. Lank, MD, emergency medicine physician and medical toxicologist at Northwestern Memorial Hospital. Dr. Lank’s research interests include novel substances of abuse and critical care of patients following overdose.

The concentration of THC in cannabis has been increasing over the past few decades, leading to a rise in cases of THC overdose. An overdose can cause nausea, vomiting, palpitations and alterations in behavior such as psychosis.

Understanding Edibles

In some states with legalized cannabis, one problem has been the limited public understanding of edible products, which are food products infused with cannabis.

“While inhaled cannabis may reach peak effect within minutes, ingested cannabis may take up to four hours. A person may eat a pot brownie and not feel anything, so they eat another brownie, assuming they didn’t eat enough the first time. But, now the first edible is kicking in, and everything is coming to a head at once,” explains Howard S. Kim, MD, MS, emergency medicine physician at Northwestern Memorial Hospital. Dr. Kim has studied the early impact of medical and recreational cannabis legalization in Colorado.

Additionally, children may see edibles and confuse them with sweets or gummies, which can lead to accidental poisoning. To prevent this from happening, Dr. Lank advises storing products in a safe location and calling poison control immediately if they are ingested by a child.

The Impact of Long-Term Use

As with other smoking or vaping products, smoking cannabis can significantly impact your lung health, damaging your lungs and increasing your risk for lung disease. It can also impact cell linings in your airways, which results in chronic cough, increased phlegm and acute bronchitis.

Research has shown that long-term cannabis use also affects brain development. This is particularly true for brains that are still developing. Pediatric and psychiatric patients are at particular risk for adverse effects. “The increased risk of chronic psychiatric disease with early exposure to cannabis is very well documented,” explains Dr. Lank. Research shows habitual use can cause loss of IQ and neuropsychological decline.

Long-term cannabis use can also impact mental health. Though research is still developing, studies suggest it is associated with an increased risk of developing psychotic disorders such as schizophrenia. It can trigger or worsen the psychotic symptoms of schizophrenia, like hallucinations, paranoia and psychosis. Scientists believe this may occur in individuals with a genetic mutation that makes them more susceptible to the effects of cannabis.

Additionally, some suggest it is a gateway drug, meaning it leads to the use of other addictive drugs. Many people don’t realize you can be addicted to cannabis, but approximately 9 percent of people who have used it have gone on to meet criteria for a substance use disorder (previously called dependence), explains Dr. Lank.

Another potential conflict is with employers who use drug testing. Cannabis remains illegal under federal law, and it’s unclear how the justice system and employers will treat this issue going forward, according to Dr. Kim. Drug testing is problematic because the results of a drug test for cannabis are not necessarily indicative of your current state of sobriety or intoxication. This is because THC is different than alcohol in that it remains in the body and may produce a positive drug test long after its clinical effects have worn off. Additionally, there is no consistent definition of what level of THC in your system constitutes intoxication. Some states define it by nanograms per millimeter, and others by clinical exam.

Long-Term Use and Cannabinoid Hyperemesis Syndrome

Although rare, chronic use can also cause cannabinoid hyperemesis syndrome, marked by uncontrollable vomiting. “Patients typically present with cyclic vomiting and abdominal pain, and they classically describe a habitual yearning for hot showers and baths,” says Dr. Kim. “It’s notoriously difficult to treat because patients falsely think the cannabis is helping their nausea, when in reality it’s the cause.”

Legal or not, cannabis impacts your health. If you are considering trying it, whether for recreational or medicinal purposes, talk to your physician first. And, if you are using cannabis, be sure to mention that to your physician.