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- Short-term effects of marijuana include red eyes, paranoia, euphoria, and an increased appetite.
- Long-term effects of weed include impaired development, memory loss, and respiratory issues.
- Smoking weed may also increase a person's risk of schizophrenia, bipolar disorder, and depression.
- Visit Insider's Health Reference library for more advice.
Marijuana can be an unpredictable drug with effects that vary based on a variety of factors including your brain's unique chemistry, the type of marijuana used, how much you consume, and your method of consumption.
For example, if you smoke marijuana, you'll feel its effects seconds after you inhale, which typically lasts for another one to four hours. Edibles, however, can take about an hour to kick in with effects lasting up to 24 hours.
Studies on marijuana's effects often show conflicting results, and its status in the United States as a federally illegal schedule one drug makes it difficult for researchers to conduct large, comprehensive studies.
With that said, here's what we know so far about the short-term and long-term effects of marijuana:
Short term effects of marijuana
Marijuana contains chemicals called cannabinoids that interact with endocannabinoid receptors in your brain and body. These receptors influence many different functions including pleasure, memory, thinking, movement, and time perception. That's why using THC, the most prominent cannabinoid in marijuana, can lead to the following effects:
1. Causes red eyes
Marijuana typically lowers blood pressure causing blood vessels to dilate, which increases blood flow. "As a result, blood vessels in the eyes expand, leading to red or 'bloodshot' eyes," says Lawrence Weinstein, MD, the Chief Medical Officer at American Addiction Centers.
2. Relieves pain
Studies suggest marijuana moderately reduces pain, particularly nerve pain, muscle spasms, and cancer. Researchers believe this is due to THC binding to multiple receptors within the nervous system and blocking the sensation of pain.
3. Stimulates appetite
Appetite stimulation is one of marijuana's most well-known effects. It is linked to THC binding to receptors which release the hormone, ghrelin, that stimulates appetite, says Weinstein.
4. Induces euphoria
Studies show THC increases dopamine in the brain, the neurotransmitter responsible for euphoria. This induces feelings of bliss commonly referred to as "feeling high."
5. Increases anxiety/paranoia
While THC can cause feelings of euphoria, consuming too much THC can cause an opposite reaction like anxiety or paranoia.
"Dose is the crucial factor. A little can be helpful, but too much is problematic," says Jordan Tishler, MD, President of the Association of Cannabis Specialists.
6. Impairs judgment
Marijuana is associated with an impaired ability to strategize, problem-solve, and make good decisions. However, the extent of this effect is dependent on several variables including marijuana potency and previous exposure to the drug.
For example, one study found chronic marijuana users performed poorly compared to non-users on tests measuring their ability to make strategic decisions.
7. Increases heart rate
After consuming marijuana, your heart rate increases to accommodate lower blood pressure and supply oxygen to the body and brain, says Weinstein. For this reason, Weinstein advises people with cardiovascular conditions, like a history of heart attack or stroke, to refrain from using.
Long term effects of marijuana
Marijuana's long term effects will vary from person to person, especially depending on how frequently you use the drug. Most of the following effects have only been documented in chronic users, which are those that use marijuana on a daily basis for an extended period of time.
8. May increase depression and anxiety
The majority of studies have linked marijuana use to an increased risk of psychiatric disorders including depression, anxiety, and schizophrenia - particularly in people pre-dispositioned to the conditions.
But, study results are conflicting: A large 2016 study found no association between marijuana use and mood and anxiety disorders. Yet, a different data sample of US adults indicated using marijuana more than once a month was associated with an increased risk of social anxiety.
"For some people, the use of marijuana can exacerbate mental health issues," Weinstein says, emphasizing this is likely based on individual factors.
Therefore, if you have a family history of mental health conditions or are already diagnosed, it's best to avoid marijuana until you consult with your doctor.
9. Harms cardiovascular health
Studies have linked marijuana use to an increased risk of:
- Heart attack
- Stroke
- Atrial fibrillation (an irregular, rapid heart rate)
However, more studies are needed to understand cannabis's health implications, says the American Heart Association.
10. Causes memory loss
A large long-term 2016 study found an association between regular marijuana use and lower scores on tests of verbal memory and processing speed.
11. May damage lungs
Some research suggests smoking marijuana can lead to symptoms like chronic cough, mucus production, and wheezing.
However, a 2012 study found chronic marijuana users who smoked one joint a day for 10 years scored well on tests measuring lung strength and capacity.
However, researchers noted a decline in lung strength after the 10 year mark, but lung capacity continued to increase with greater lifetime exposure to marijuana.
12. Helps with weight loss
While cannabis can stimulate appetite, multiple studies show an association between long-term cannabis use and a reduced body mass index (BMI), even in users who eat more calories than non-users.
The average American diet is characterized by high intakes of sugar and starchy foods, which researchers theorize can cause an imbalance in the body's endocannabinoid system. Cannabis is believed to "reverse" this imbalance, causing the body to burn and store calories more efficiently.
13. Impairs development
Marijuana's effects on brain development are unclear and likely vary based on:
- Age when you start using
- How much you use
- What type of marijuana you use
- Genetics
Most studies suggest regular marijuana use in teenagers is associated with reduced volume in certain regions of the brain which could lead to reduced brain function. However, others note no structural differences between the brains of marijuana users versus nonusers.
14. Increases risk of addiction
The Center for Disease Control (CDC) suggests one in 10 marijuana users will become addicted. That number increases to one in six in people who begin using before age 18.
Like other addictive drugs, THC is associated with dopamine release which "teaches" the brain to continue using it.
Insider's takeaway
The effects of marijuana will vary based on the individual. Common short-term effects of marijuana include euphoria, red eyes, paranoia, and increased appetite, while in the long-term it could impact your lung, heart, and brain health.