Dr. Laura Foster
Family Physician

Short Term Effects

Although cannabis affects people in different ways, short term effects can include: feeling happy, relaxation, increased sociability and heightened sensation. Problems with memory and learning, distorted perception (sights, sounds, time, touch), trouble with thinking and problem solving, body tremors, loss of motor coordination, increased heart rate and anxiety and panic attacks. These effects may be even greater when other drugs are mixed with cannabis. 

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Long Term Effects

Regular cannabis use in adolescents is associated with experiencing psychotic symptoms (changes in thoughts, feelings and behaviours), especially when there is a family or personal history of psychotic disorders. Some studies have suggested that cannabis may also increase risk of anxiety and depression.

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What’s regular cannabis use? Regular use of cannabis means that the use of cannabis occurs regularly over time. It may involve using cannabis every day, or every weekend over a period of several months or over a number of years.

Early and frequent cannabis use is linked with poor performance in school, lower grades and increased risk of dropping out. Some research suggests that early, regular, heavy and long-term use of cannabis by teens may impair their cognitive abilities and may not be fully reversible. 

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Youth might be particularly vulnerable to these negative outcomes due to the extensive changes that are taking place in the brain during adolescence, especially the ongoing development and maturation of the prefrontal cortex, which is critical to higher-order cognitive processes such as impulse control, working memory, planning, problem solving and emotional regulation.

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Adolescence is a period of major risk for the onset of Substance Use Disorders.  Generally,the peak age of onset of Substance Use Disorder is between ages 18-20. The peak age of onset for Cannabis Use Disorder or CUD is younger, 16-18 years old. 

How Cannabis Use Disorder affects adolescents:

• • Acute panic reactions or mild paranoia have been observed.

  •  May also lead to an acute toxic psychosis accompanied by loss of insight.

  • Heavy and frequent marijuana use (daily use in past 30 days) is associated with significantly greater impairment than light use (1-9 days of use in past 30 days) on attentional and executive functions.

  • Short-term/working memory impairment may persist for some time on neuropsychological testing (up to 3 months).

  • Solid evidence that persistent regular cannabis use (4 day/week) and/or dependence in adolescence is associated with broad based neuropsychological decline in adulthood.

  • Greater the duration of use the greater the decline

  • Negative impact on functioning

  • Cessation of cannabis did not fully restore neuropsychological profile, even after controlling for years of education.

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Cannabis, just like any other drug, can lead to addiction. It affects the brain’s reward system in the same way as all other drugs of addiction — and the likelihood of developing problem use or addiction increases considerably for those who start young.