Some states have legalized the possession and use of marijuana even though it remains illegal in the eyes of the US government. While support is growing for the use of marijuana for medicinal purposes, it is still used as a drug of abuse. As with alcohol, marijuana has a number of negative biological and psychological side effects.

Short Term Effects

Someone using marijuana may experience the following:

  • Physical relaxation
  • Mild euphoria
  • Reduced motor coordination
  • Decreased ability to process information

People that are acutely intoxicated will have distorted perceptions of the world. Most curious of these is the distorted perception of time. These distortions can be so profound that it may seem to the user like hallucinations (though the experience is not a true hallucination).

Like alcohol intoxication, marijuana can impair coordination and cause difficulty with thinking and problem solving.

Short Term Damage

Marijuana can negatively affect learning and memory. In chronic users especially, this disturbance in cognitive performance can last for days to weeks after an acute intoxication.1 In other words, those that use marijuana routinely may experience problems learning new and remembering learned information, even if they are not currently “high.”

While marijuana is a relaxant, the drug can speed up your heart rate, up to double its normal rhythm.  In people that have underlying heart problems, marijuana is a rare cause of myocardial infarction (heart attack).  More frequently, smoked marijuana leads to abnormal heart rhythms and chest palpitations.

Long Term Damage

Because of marijuana’s intermediate and long term effects on learning and memory, chronic users may be undermining their own mental performance.

Since the negative effects last longer than the acute intoxication, habitual users are in a constant state of mental slowness, exhibiting poor performance on various tasks.

According to researchers Fergusson and Bodenn 2, long term marijuana use leads to “poorer educational outcomes, lower income, greater welfare dependence and unemployment and lower relationship and life satisfaction,”4

Smoked marijuana can also cause many of the same problems suffered by those that chronically smoke tobacco cigarettes. While it is unclear whether marijuana leads to increased rates of lung cancer, chronic smokers of marijuana develop chronic obstructive pulmonary disease (COPD) and pneumonia more frequently than those that do not smoke any substance.

While it is widely believed that marijuana is not addictive, long term use of the drug certainly causes a mild to moderate physiological and psychological dependency. 

In fact, the drug is addictive if you define addiction as compulsively seeking a substance despite its harmful effects.

Heavy, chronic marijuana users report withdrawal symptoms when they stop using the drug, such as a change in appetite, craving and sweating. While marijuana withdrawal is more uncomfortable than it is dangerous, it may interfere with efforts to stop using the drug.


There have not been any confirmed, reported cases of overdose on marijuana alone, but it has been detected in the blood and urine of people that have overdosed on other drugs, such as cocaine and heroin. Marijuana cigarettes laced with other substances can cause overdose (but overdose from the laced substance).

Symptoms and Signs of Abuse

Marijuana is usually smoked as a self-made cigarette called a joint or a “blunt” fashioned from the paper of a hollowed-out cigar.  Marijuana may also be smoked using a pipe or bong.

Drug paraphernalia are a strong indicator of use and abuse:

  • A marijuana pipe (sometimes called a bowl) is smaller than a traditional tobacco pipe and may take many shapes
  • A bong is larger and more complicated in design and usually has a water reservoir

In addition to physical items associated with abuse, one may recognize marijuana use by its negative effect on school and social functioning.  Moderate and heavy users may exhibit signs of withdrawal and apathy. Grades in school or work performance may suffer because of a lack of motivation and ongoing cognitive deficits.

Adverse Interactions

The reports of drug interactions with marijuana are exceedingly rare. Single case reports have documented interactions with antidepressants,cancer chemotherapeutics,3 and the blood thinner, warfarin.4


Find a rehab that specializes in treating marijuana addiction.



1  Pope HG, Jr., Gruber AJ, Hudson JI, Huestis MA, Yurgelun-Todd D. Neuropsychological performance in long-term cannabis users. Arch Gen
2  Fergusson DM, Boden JM. Cannabis use and later life outcomes. Addiction. Jun 2008;103(6):969-976; discussion 977-968.
3. Russmann S, Winkler A, Lovblad KO, Stanga Z, Bassetti C. Lethal ischemic stroke after cisplatin-based chemotherapy for testicular carcinoma and cannabis inhalation. Eur Neurol. 2002;48(3):178-180.
4.  Yamreudeewong W, Wong HK, Brausch LM, Pulley KR. Probable interaction between warfarin and marijuana smoking. Ann Pharmacother. Jul 2009;43(7):1347-1353.