What are the Short- and Long-Term Side Effects of Regular Use of Cannabis?

What are the Short- and Long-Term Side Effects of Regular Use of Cannabis?

You won’t find solid science to identify the short and long-term side effects of regular use of cannabis. The anecdotal history dates back millennia. And, the stigma attached to cannabis use severely curtails the research necessary.

That leaves you with OpEd pieces such as this, trusting the argument is clear and supported by the best evidence out there.

The intellectual problem

Absent long-term research studies with double-blind protections, there is a significant intellectual problem distinguishing between causation and correlation. Proving a causal connection between events takes disciplined scrutiny.

Until the dawn of the scientific method, philosophers have dominated causation. But, an examination of cannabis’ effects is a function of epidemiology. So, the focus tries to show a probabilistic connection between event 1 (cannabis) and event 2 (side-effect).

Correlation, on the other hand, measures parallel events. It might examine how event 1 would lead to event 2 in certain circumstances as opposed to others. For example, does event 2 follow from event 1 in adolescents more than adults?

In research, the scientists would prefer to reach causal conclusions, but correlations can expand the data and information.

While anecdotal evidence only confirms such findings by coincidence, it can provide a starting point in posing the right questions. For instance, if X number of people report relief of nausea attached to chemotherapy, there may be a cause and effect connection.

So, you can appreciate the effort here to identify the short- and long-term side effects of regular use of cannabis.

Short-term effects

Most cannabis users acknowledge short-term side effects as dry mouth, reddened eyes, and dry cough. But, there can be more short-term side effects depending on the individual user and cannabis strain. In most cases, “short-term” means within minutes or 24-hours:

  • Cannabis may alter working memory and spatial memory. You may find it difficult to focus or concentrate on thoughts or continue a mental process. An increased sensual perception may change your perception of time and space, color and sound.
  • Another user or another strain may improve focus and attention. High THC will reduce focus, but high CBD may improve it. The CBD density may, indeed, help patients with ADD/ADHD and on the Autism Spectrum.
  • Cannabis use may produce brain fog, drowsiness, or fatigue. That same influence on spasms, anxiety, inflammation, and smooth muscle can adversely affect erectile dysfunction.
  • Panic, hallucinations, extreme anxiety, and paranoia may follow use, but they are a function of cannabis strain content and/or a predisposition to such conditions.
  • As a likely correlation with reduced inhibitions, Psychology of Addicted Behaviors published a study concluding, “sexual enhancement expectancies showed significant, positive associations with frequency of marijuana use, marijuana use at last intercourse, and intentions to have sex while using marijuana in the future. Higher sexual risk expectancies predicted significantly lower intentions to use condoms while having sex under the influence of marijuana in the future.”

Long-term effects

  • Cannabis User Disorder (CUD): Chronic use can indicate CUD, a dependency syndrome. If not technically an addiction comparable to the functional or incapacitating addictions to alcohol, cocaine, heroin, meth, or opioids, CUD is a psycho-physical problem subject to withdrawal, depression, anxiety, and insomnia. This is especially true when, as may be the case, the long-term use of cannabis mixes with use of alcohol or other drugs.
  • Chronic cannabis use has been linked with adverse cognitive development in adolescents. In 2013, a review of the literature suggested the following:

 ♦ There are neurocognitive disadvantages to using marijuana in the domains of attention and memory that persist beyond abstinence,

 ♦ changes in white matter tract integrity,

 ♦ and abnormalities of neural functioning.


“Earlier initiation of marijuana use (e.g., before age 17) and more frequent use has also been associated with poorer outcome.” Subsequent research has accepted the accuracy of these assessments, but research routinely recommends additional research on how this “damage” may affect adults or continue beyond sustained abstinence

♦ Cannabis use may increase the risk of developing schizophrenia and other psychoses; the higher the use, the greater the risk.

♦ In individuals with schizophrenia and other psychoses, a history of cannabis use may be linked to better performance on learning and memory tasks.

♦ Cannabis use does not appear to increase the likelihood of developing depression, anxiety, and posttraumatic stress disorder.

♦ For individuals diagnosed with bipolar disorders, near-daily cannabis use may be linked to greater symptoms of bipolar disorder than for nonusers.

♦ Heavy cannabis users are more likely to report thoughts of suicide than are nonusers.

♦ Regular cannabis use is likely to increase the risk for developing social anxiety disorder.

But, research has not differentiated the reciprocity here. That is, the disadvantageous behaviors may be more likely in those who use, or those who use may be more inclined to the problem.


  • Studies have linked chronic cannabis use with the occurrence of testicular tumors, but the most recent research in BMC Cancer (2015) concludes, “We found inconclusive evidence regarding the relationship between cannabis use and the development of seminoma tumors.”
  • Smoking cannabis on a chronic basis may occasion other cardiopulmonary and/or respiratory conditions. But, no science differentiates its role from smoking cigarettes. It seems common sense to moderate inhaling any combustible material.

What are the short- and long-term side effects of regular use of cannabis?

The question is too vague for scientific inquiry. There are too many variables, cofactors, and associations at work.

You can assume, however, that the continuous and heavy use of any inebriant or psychoactive substance puts the user at risk. The classic pothead is not a role model for most people. More importantly, the pothead, who has rejected or co-opted from most societal expectations, may already be risking physical and psychological. It doesn’t make the chronic user a bad dude, but you shouldn’t bet on his/her long-term well-being.