Marijuana Use: Therapeutic Benefits and Health Risks Explained
Alongside tobacco, alcohol, and cocaine, cannabis is one of the most widely used drugs in the world. It’s estimated that about 2% of the global population uses cannabis daily. In many U.S. states, cannabis has been legalized because of its recognized therapeutic properties.
Some of the most commonly reported medical benefits include:
- Reducing chronic pain
- Relaxing muscles
- Anti-inflammatory effects
Because of these qualities, cannabis is often considered a complementary therapy for people undergoing chemotherapy, as it may help ease side effects such as nausea, loss of appetite, and pain.
But despite its potential medical applications, frequent cannabis use carries serious health risks, especially due to the presence of THC (tetrahydrocannabinol)—the main psychoactive compound in cannabis. THC distorts perception of reality, impairs judgment, and is also the component responsible for cannabis addiction.
According to the 2021 National Survey on Drug Use and Health (NSDUH), about 18% of Americans aged 12 and older reported using cannabis in the past year, with young adults (18–25) being the highest users. This means millions are exposed to THC and its effects every year.
Using cannabis can cause noticeable effects within minutes, and these can last for several hours. Common short-term effects include:
- Slower reaction time and reduced psychomotor skills
- Impaired reasoning and decision-making
- Short-term memory loss
- Difficulty learning new information
- Anxiety, paranoia, or panic attacks
- Mood changes such as fear or depression
- Faster heart rate (increasing cardiac risk in some people)
- Hallucinations (with high doses)
With repeated or heavy use, cannabis can lead to more persistent health problems. Long-term risks include:
- Reduced concentration and attention span
- Lasting decline in cognitive ability and learning performance
- Persistent memory problems due to loss of neurons in the hippocampus (the brain region tied to memory)
- Increased aggression and loss of self-control in some users
- Daytime sleepiness and reduced motivation
- Higher risk of psychotic episodes or mental health disorders in vulnerable individuals
- Difficulty maintaining healthy social relationships
- Dependence and, in many cases, progression to use of other substances
Experts warn that cannabis use is particularly harmful during adolescence, when the brain is still developing. Repeated cannabis use at this stage can cause permanent changes to memory and learning capacity.
A 2012 study in Proceedings of the National Academy of Sciences (PNAS) found that people who began using cannabis heavily in adolescence and continued into adulthood showed a significant drop in IQ (up to 8 points) compared to non-users. This decline was not fully reversible, even after quitting.
The National Institute on Drug Abuse (NIDA) also highlights that cannabis disrupts communication between neurons in the hippocampus, impairing short-term memory and learning — key functions during school years.
Dr. Nora Volkow, Director of NIDA, has emphasized:
“Cannabis use during adolescence is particularly concerning because the brain is still developing, and THC can disrupt critical processes that shape cognitive and emotional function.”
The American Psychiatric Association states that cannabis use can increase the risk of developing schizophrenia and other psychoses, particularly in people with a family history of mental illness.
A 2020 review in JAMA Psychiatry concluded that frequent cannabis use in youth is associated with higher rates of depression, suicidality, and poor educational outcomes.
For those considering cannabis use, here’s what health professionals recommend:
- If you’re under 25, avoid regular use. The risks to memory, learning, and mental health are significantly higher during brain development years.
- Use only under medical guidance if prescribed for chronic pain, chemotherapy side effects, or other approved conditions.
- Avoid high-THC products. Strains or concentrates with high THC levels are linked to stronger dependence and mental health risks.
- Watch for warning signs such as memory problems, lack of motivation, anxiety, or paranoia — which may signal harmful use.
- Seek help early if dependence develops. Behavioral therapy and counseling have been shown to be effective in helping people quit.
Cannabis is a complex drug: it may offer medical benefits for some people, but frequent or heavy use—especially during adolescence—can have lasting negative effects on memory, cognition, and mental health.
In the U.S., where cannabis is increasingly legal, it’s essential to approach use with caution and awareness of the risks. Talking with a healthcare provider can help weigh the potential benefits against the possible harms.