Cannabis is one
of the drugs that has been used for years and nowadays it is the most common
drug used by teenagers. Adolescents who use cannabis very often have a chance
of affecting their brain functions. There are many studies that show the side
effects of cannabis on individuals’ behaviour and their cognitive performance,
mainly adolescents who consume neurotoxic substances before the age of 15 where
the brain is still developing. One of these studies is the experiment focused
by Fontes, et al. (2011). This analysis was based on 104 participants who
started consuming cannabis in their early adolescence and those who started
consuming it later (before and after the age of 15). The hypothesis of this
experiment was that teenagers consuming cannabis before the age of 15 will not perform
well on the cognitive tests given.


The article by
Fontes, et al. (2011) focuses on the 104 participants who were cannabis users
and were following a treatment at the Drug and Alcohol Unit at the University
of Sao Paolo. These 104 individuals were divided in three groups. The first
group were the early onset who started consuming chronic cannabis before the
age of 15. The second group were the late onset, individuals who started consuming
cannabis after the age of 15. The third group were the non-users who had not
used cannabis at all in the last 3 months and had not used it more than 5
times. Neuropsychological tests were performed by the participants. These
assessments were formed of a vocabulary and block design (WAIS-R) for IQ
estimation, a Stroop test (assess their cognitive speed and control), a
Wisconsin Card Sorting Test (help to measure individuals’ competence ability to
solve problems) and a Frontal Assessment Battery- FAB (a cognitive and
behavioural test to evaluate the frontal lobe functions).


This study
verifies that the early onset group did not performed well in some tasks
compering with the other groups. However, there was not a huge difference
between early onset and late onset group. Overall, there were not any diversity
between all three groups in the IQ test, WAIS-R test and block design. During
the WCST test, compering with the control group, the early onset did not complete
all the categories and they made repetitive errors. This clearly demonstrate that
individuals consuming cannabis before the age of 15 are not incompetence on
planning, managing skills or even solving problems. In the FAB test the results
showed that the performance of the early onset was worse comparing with the late
onset and control group. A difference of 0.97 compering with the late onset and
1.24 with the control group. The results showed that the early onset are not
able to assess executive functions. While during the Stroop test there was a huge
difference in the score, where the control group scored lower (15.64) than the
early onset (18.20).


As can be seen,
the results demonstrate that chronic cannabis users before the age of 15 tend
to have a side effect on the brain development as the brain is still developing
in that stage. In effect, the hypothesis of this study is right as the early
onset group performed poorly in most of the tasks.     

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