Since marijuana is gaining popularity in the United States, it is advisable to know how it affects users' health. As of Jan. 4, 2019, 10 states have fully legalized cannabis usage for adults, and 33 others have medical marijuana laws in place(1).

Like any foreign substance added to the body, marijuana can affect a person's brain, heart, gastrointestinal, and lung health. Tetrahydrocannabinol (THC), the active ingredient in cannabis, is addictive and increases the risk of mental health complications(2).

Moreover, even though many consumers use marijuana to cope with their pain, there is little known about the drug's effect in treating chronic pain.

Short and Long-Term Effects of Marijuana on the Brain

The short-term effects begin when a person smokes THC. It rapidly moves through the lungs into the bloodstream, which carries the cannabinoid to the brain and other organs(3). When the substance is consumed as a food or beverage, there is a delay in its side-effects, up to an hour later.

The chemical is processed in the brain by endocannabinoid neurotransmitters that usually respond to natural THC-like chemicals, which play a part in brain maturation and function. Cannabis overstimulates the brain's parts with the highest concentrations of receptors giving consumers that "high" feeling.

These areas direct movement, sensation, vision, judgment, reward, memory, and coordination. When marijuana is taken in high doses, the side effects may include hallucinations, delusions, and psychosis.

When teens begin using cannabis affects their brain's development, the drug could decrease attention, memory, and learning functions and how the brain builds connections between the areas necessary for these functions.

These deficiencies may last a short time or be permanent vary depending on various factors such as the individual, how much THC was used, and the length of time it was used.

THC Dependency and Addiction

THC dependency occurs when the brain becomes used to the added chemical, thereby reducing its own neurotransmitters' productivity.

While there are no hard statistics on marijuana dependency, common characteristics of withdrawal are evident after quitting and can last a couple of weeks(4). Symptoms experienced are grumpiness, mood and sleep problems, lack of appetite, cravings, restlessness, and/or various forms of physical pain.

Whereas marijuana addiction is defined by a person's inability to quit using the substance; choosing it over their family, friends, co-workers, and employers; as well as making excuses and lying. Another sign of addiction is continuing to use marijuana, knowing it is causing problems in their life.

The National Institute of Drug Abuse (NIDA) reports a lack of precise data supporting exact percentages of marijuana addicts among users in the United States since these often treat dependence as addiction, even though there is a distinct difference.

However, the consensus is 10 percent of adult users will suffer from dependency(5). The percentages increase to 16 when consumption begins before the age of 18.

The 2015 National Survey on Drug Use and Health results indicate that nearly 4 million respondents met the criteria for marijuana use disorder. Of those, 138,000 sought treatment for their addiction.

Once a person becomes addicted to marijuana, their mental health can spiral downward(6). Drug abuse will increase depression, anxiety, hopelessness, suicidal ideation, rapid-cycling thoughts, and impulsiveness. These symptoms will worsen as the disease grows, and for those with mental health illnesses, the outcome could be more significant.

Mental Health Complications When Using Marijuana

Most cannabis users will not experience serious mental health issues; a small percentage of consumers will find their symptoms triggered. Marijuana is the drug most frequently used by those with mental health illnesses.

Those who suffer from episodes of clinical depression could see an increase in the frequency of the illness. The risk is proportionate to the amount and rate of marijuana consumed. Researchers warn THC usage may exacerbate depressive symptoms.

Marijuana consumption by those diagnosed with a bipolar affective disorder (BAD) diagnosis could experience an uptick in manic episodes with increased symptomology. In rare cases, cannabis-induced bipolar disorder may be triggered by marijuana misuse in those who have not previously been diagnosed.

Researchers cannot explain with any surety whether a person had underlying/untreated BAD or if the drug caused the illness. They further advise those with bipolar disorder that there is a complex relationship between marijuana and the illness that is not clearly understood.

In 2011, more than 33 percent of those seeking help in emergency rooms experienced marijuana-related psychosis. One-third of 6,800 individuals suffering from this psychosis later developed schizophrenia or bipolar disorder(7).

For users taking SSRI antidepressants, cannabis increases the risk of manic episodes. Like those prescribed for heart conditions or asthma and COPD, the effectiveness of medications may be compromised when combined with marijuana.

Effect of Cannabis on Heart and Respiratory Health

A person's heart speed rate increases, and their breathing passages open within minutes of inhaling marijuana. Smoke irritates the throat and lungs. The result is a forceful cough during use and phlegm production.

A typical heart rate range is 70-80 beats per minute, but after inhaling, a person's heart rate can jump by 20-50 bpm(8). In some cases, this number can double. It could take up to three hours before a heartbeat will resume normal rates.

Smoking may also raise the chance of stroke or developing cardiovascular disease. Limited data indicates the normal risk of suffering a heart attack is multiplied fivefold within the first hour after smoking.

THC users must consider a head rush or dizziness on standing up, which may increase the danger from fainting or falling. A person can develop a tolerance to some cardiovascular effects with repeated exposure.

Marijuana, like cigarettes, contains volatile chemicals and tar. While unconfirmed, scientists are concerned about the risk of cancer and lung disease. Cannabinoid smoking is linked to large airway inflammation, increased airway resistance, and lung hyperinflation. People who smoke marijuana regularly report more symptoms of chronic bronchitis than those who do not smoke.

When cannabis smokers stop, so do the side effects of lung and throat irritation, as well as bronchial inflammation(9).

Gastrointestinal Health While Using THC

THC is proven to relieve nausea and vomiting in patients undergoing chemotherapy. Paradoxically, Cannabinoid Hyperemesis Syndrome (CHS), in 2011, a new clinical condition has surfaced with the onset of cannabis abuse(10).

Although CHS is considered rare, there is a consensus among experts that it is misattributed as Cyclic Vomiting Syndrome. The two share similar symptoms and are often confused.

Researchers indicate the syndrome is caused by unknown means. However, three cannabinoids found in the cannabis plant have opposing effects on the vomiting response.

  1. Business Insider, Jan. 24, 2019; This map shows every US state where pot is legal
  2. NCBI, Oct. 17, 2009; Adverse health effects of non-medical cannabis use.
  3. NIDA; June 2018; DrugFacts Marijuana
  4. NIDA; Is Marijuana Addictive
  5. CDC; Marijuana and Public Health; Marijuana: How Can It Affect Your Health?
  6. NIDA; Marijuana; What are marijuana’s effects on other aspects of physical health?
  7. NIDA; Marijuana; What are marijuana's effects on lung health?
  8. NCBI; Dec. 4, 2011; Cannabinoid hyperemesis syndrome.