In the 2016
Monitoring the Future study, about 45.3 percent of high school seniors
reported having used marijuana once or more in their lifetime and about
23 percent used in the past month.
It’s no surprise that marijuana is the second most abused drug by teenagers in the United States, after alcohol. With this high rate of use, many teenagers and some adults believe that marijuana is harmless, especially in states where marijuana is now legal.
However, several studies are discovering common links between chronic marijuana use in adolescence and long-term physical, mental and behavioral problems that develop in adulthood.
Cognitive Problems with Chronic Use
Memory Loss
A recent
Northwestern University study found that 18 percent of young adults who
chronically abused marijuana as teens performed worse on their memory
tests than young adults who had never abused the drug.
The same
study also found that teens who smoked marijuana daily for about three
years experienced a structural change in the brain that reshaped the
hippocampus. The hippocampus is the part of the brain that controls
memory function. Since teens’ brains are not fully developed yet,
chronic use of marijuana may have a lasting effect on memory.
Decrease in IQ
There is also
some evidence of declining IQ over time for marijuana users who began
using in their teens and continued into adulthood. A study in the
Proceedings of the National Academy of Science of the United States of
America suggests a decline in brain function over time.
In this
study, they compared marijuana users and non-users in adolescence
through age 38. They found that the adults who began using as teens and
for many years after, decreased eight IQ points from childhood to
adulthood; however many had low IQs to begin with.
There are
many conflicting studies out there regarding teen marijuana use and
extensive research is needed. However, these studies suggest abnormal
brain structure is linked to chronic marijuana use beginning in
adolescence into adulthood.
Short- and Long-Term Effects in Teens
Short-term Effects
The
short-term effects of marijuana use are well known and very visible.
Depending on the potency of marijuana and frequency of use, every
individual’s reaction may differ. Short-term effects include:
- Dizziness
- Dilated pupils
- Red eyes
- Acting silly for no reason
- Lack of motivation/interest
- Slow response
- Being hungry and eating more
Long-term Effects
Multiple
studies have found that teens who chronically use marijuana experience a
structural change in the brain. This structural change contributes to
more cognitive problems with prolonged use of marijuana such as:
- Memory loss
- Lack of attention and problem-solving skills
- Lower intelligence
- Declining school/work performance (absences, poor grades)
- Behavioral problems (increased promiscuity, DUIs, criminal behavior)
- Mental health problems (moodiness, anger, anxiety)
Developing Research on Teen Marijuana Use
Since teens’
brains are still developing, the high levels of THC in marijuana has
been shown to disrupt their normal brain functioning and may have
lasting effects. While there is a lot of conflicting information about
the effects of marijuana use in teens, more research is needed.
The previous
studies provoke many questions from other researchers. Longer research
studies are in progress to determine whether chronic marijuana use in
teens is linked to more permanent cognitive impairment in adulthood.
Meanwhile, parents should be aware of these new developments as the long-term effects of marijuana may cause more alarming concern in teen development.
For more information on the effects of Teen Marijuana Use see our Marijuana Dependence page.