critically

Cannabis is
commonly referred to as an innocuous drug and the prevalence of lifetime and
regular use has increased through time. However, accumulative evidence
highlights the risk of dependence and other adverse effects . It is widely
accepted that cannabis use can cause mental health issues such as
schizophrenia, bipolar and psychosis. There are approximately 400 chemincal
compounds in an average cannabis plant. The four main compounds within the
plant are called delta-9-tetrahydrocannabinol, cannabidiol,
delta-8-tetrahydrocannabinol and cannabinol. Each of these compounds are
psychoactive, apart from cannabidiol, the strongest compound being
delta-9-tetrahydrocannabinol. When cannabis is smoked, its compounds
immediately enter the bloodstream which is then transported to the brain. (Borgelt,
Franson, Nussbaum, & Wang, 2013). The
delta-9-tetrahydrocannabinol binding to cannabinoid receptors in the brain
results in the feeling of being ‘high’. A receptor is a site on a brain cell
where certain substances can stick or bind for a certain amount of time, this
will then have an effect on the cell, producing nerve impulses.

An association
between the use of cannabis and the risk of schizophrenia was studied in a
follow up of Swedish conscripts. Arguments were raised that this association
was due to the use of drugs such as cannabis. A dose response relationship was
assessed through the use of cannabis at the age of 18, and schizophrenic
diagnosis 15 years later. Self reported heavy cannabis users were more likely
to develop schizophrenia 15 years later compared to non cannabis users. However,
more than half of these heavy users had a psychiatric diagnosis other than
psychosis. Very few cannabis users went on to develop schizophrenia which
suggests that cannabis is most likely to develop schizophrenia with those who
are vulnerable to developing psychosis. Studies continue to find the
association between the use of cannabis and the presence of schizophrenia.
Zammit et al reported a 27 year follow up study of the Swedish cohort study
that had also found a dose-response relationship between the use of cannabis
and the risk of schizophrenia. The link between the use of cannabis and the
presence of schizophrenia persisted when researchers had statistically
controlled the effects of other drugs and potential confounding factors which
include a history of psychiatric symptoms at baseline. They had estimated that
schizophrenia could have been avoided within 13% of these cases if the users
have prevented the use of cannabis. Zammit et al’s findings were supported in a
three year longitudinal study conducted by Van et al. Van et al had studies the
relationship between cannabis use and psychosis with 4, 848 participants in
Netherlands. Van et al had found that cannabis use at baseline predicted a
higher change of developing psychotic symptoms during follow up periods in the
individuals who had not predicted these symptoms at baseline. He had found a
dose-response relationship between the use of cannabis and the presence of
psychotic symptoms during the follow up periods. Participants who had reported
psychotic symptoms at baseline were more likely to develop schizophrenia
compared to those who were not as vulnerable. These findings suggest that
regular cannabis use predicts an increased risk of developing schizophrenia as
the relationship persists after controlling for confounding variables.

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The association
between cannabis dependence and the presence of psychotic symptoms was examined
on participants between the ages of 18 and 21, controlling for potential
compound factor such as previous psychotic symptoms. The findings of this study
suggested that the participants who met diagnostic criteria for cannabis
dependence at the age of 18 were 3.7 times more likely to develop psychotic
symptoms compared to those without cannabis dependence. Those who were at the
age of 21 were 2.3 times more likely to develop psychotic symptoms compared to
those who were not cannabis dependent. This study lacks information on the
frequency of cannabis use, therefore it is difficult to assess if heavier doses
or using cannabis for a longer period of time is strongly associated with
developing psychotic symptoms.

A seven wave
cohort study was conducted in the Australian state of Victoria. The
participants were randomly selected from two classes within 44 schools drawn
from catholic, government run and independent schools. One class from each
school entered the cohort in the latter part of the ninth school year (wave 1),
early in the 10th school year, the second class would enter (wave
2). The participants within the study were subsequently reviewed at six month
intervals for the next two years (wave 3 to 6), with a final follow up (wave 7)
at the ages of 20-21. Within the waves of 1 to 6, participants used laptop
computers to self administer the questionnaire, and those who were absent were
followed up by telephone. The seventh wave of data collected consisted of
computer assistant telephone interviews. 1947 of 2032 participants of the study
(95.8%) participated at least once during the first six wave. Clinical
interview schedules were used to assess depression and anxiety at each wave.
The schedule provides data on the frequency, persistence and intrusiveness of
14 common psychiatric symptoms. Cannabis use on the basis of self reported
frequency was assessed in the first six months of waves 1 to 6 and the 12
months of wave 7. This was classified as never used, less than weekly use,
weekly use and daily use. 66% of male participants and 52% of female
participants had reported using cannabis at some time. 71 male participants and
188 female participants reported depression and anxiety. The prevalence of
depression and anxiety increased with higher extents of cannabis use. Daily use
in female participants predicted higher likelihood of later depression and
anxiety. Adolescent cannabis use has been associated with the use of other
substances and an increase in risk of later drug abuse and dependence. While
this affiliation may be attributable to the prolonged use of cannabis,
researchers have theorized that this affiliation may be due to the substances
impact of the developing brain (Jacobus et al, 2009). High rates of participation and the frequent measure
during the participants teenage years draw the strengths of this study. Possible
explanations for the high level of anxiety and depression found mainly in the
female participants may be the effect that the self medicated cannabis has on
mental health. Cannabinoid receptors are found widely in the central nervous
system, with a distribution that is consistent with the brain area that is
responsible for functioning emotion and cognition (Ameri A, 1999).

However, these
theoretical findings differ from studies that use medicinal cannabis in order
to treat schizophrenia. The complex nature of schizophrenia which includes
multiple brain neurotransmitters leads to the search of effective drugs.  Participants ages 18-50 who had been diagnosed
with schizophrenia were eligible to this study. All 42 participants of this
study were inpatients of the Department of Psychiatry and Psychotherapy of the
University of Cologne. Participants were hospitalized at baseline and were
assessed for 28 days after random assignment to treatment. 37 of these
participants were suffering from acute paranoid schizophrenia and the other 5
were initially diagnosed as suffering from schizophreniform psychosis, but were
followed up and also diagnosed with paranoid schizophrenia after the study had
been completed. Participants who had a positive urine drug results for the use
of illicit drugs in general and cannabinoids were unable to participate in the study
to avoid the interaction of currently active cannabinoids, including
cannabidiol. The study objective was to determine whether the use of
cannabidiol during the period of 28 days was non-inferior to Amisulpride in the
treatment of patients with schizophrenia. Antipsychotic patients were selected
to receive 200mg of either Cannabidiol or Amisulpride four times per days, with
a total of 800mg daily. The treatment was maintained for 3 weeks. A reduction
from 800mg to 600mg was allocated to patients who received unwanted side
effects after week two, which had included three patients in the cannabidiol
treatment and five in the Amisulpride treatment. The Positive and Negative
Syndrome Scale was used to measure the assessment of psychotic symptoms at
baseline, day 14 and day 28. The results of this study suggested that
cannabidiol was as effective at improving psychotic symptoms as well as the Amisulpride.
They had found a statistically significant association between the increase in
anandamide levels and decrease in psychotic symptoms in patients treated with
cannabidiol. These findings suggest that although the use of medicinal
cannabinoid can rather decrease the presence of mental health issues such as
schizophrenia. This study uses a different administration of cannabidiol as
edible routes are now more common. This reflects more current trends in
marijuana use and looks at different effects it may cause.

A
harm-reduction approach to alcoholism was seen to be the substitution of
cannabis. 92 participants were identified as using cannabis to treat alcohol
abuse and related problems. Follow up visits, being 12 month intervals were
provided to the patients in order for them to evaluate their status as
“improved”, “stable” or “worse” as well as their efficacy of cannabis from
“very effective to “ineffectual”. Twenty-six patients reported the use of
cannabis treating depression, anxiety and stress. Research on self-reported
reasoning for using drugs such as cannabis supports this idea. However it can
be argued that other factors such as peer group influences, poor social
functioning and poor social skills could increase the likelihood of mental
disorders which leads to the use of drugs to find a solution for their
disorders. (Taylor D, Warner R, & Wright J, 1994). The self-medication
hypothesis is supported by suggestions from controlled studies that cannabis
improves mood, therefore individuals who are depressed at baseline are more
likely to begin, continue or increase their use of cannabis during follow-up
periods. Also, this study does not assess the amount of cannabis use. There may
be regular users who use a small amount of marijuana, as well as les frequent
users who tend to use a larger amount of cannabis, therefore the amount of
cannabis used would distinguish the effect it would cause.

Questions
remain about the level of association between cannabis use and mental health
issues. Findings have provided conflicting evidence on the association between
cannabis use and depression. A study which had used participants from a primary
care sample had found that among females only, the use of cannabis had double
the risk of depression (Rowe M, Fleming M, Barry K, Manwell L. & Kropp S
(1995). A study, consisting of 88 high school seniors have found that among
cannabis users, greater suicidal thoughts were arising more compared to those
who had not used cannabis (Field T, Diego M & Sanders C, 2001). In
contrast, a study which had consisted of 19-21 year olds have found no
difference between light and heavy users in the number of depressive symptoms.
With two groups of participants, 45 ‘heavy users’ (used cannabis daily for at
least two years) alongside other illicit drugs and 44 ‘occasional users’
(participants who had never used cannabis more than 10 times a month) were
examined and had reported no significant difference between the groups in rates
of any psychiatric diagnosis (Gruber S, Kouri E, Pope H & Yurgelun T D, 1995).
It is difficult to generalize the findings of these studies as there are
limitations with the measures of cannabis used in the research. The study had
groups cannabis alongside other illicit drugs, therefore it is difficult to
specify the contribution that the cannabis had made as it is mixed with other
active drugs within the body. This study does not also compare cannabis users
with non-users, therefore it makes it unclear to distinguish if the cannabis
causes the depression.

It is
reasonable to conclude that several studies found a consistent increase in
incidence of mental health issues in individuals who had used cannabis. Studies
tended to report larger effects of cannabis for more frequent use, as most
studies had showed a 50-200% increase for those who tended to use cannabis on a
more frequent level, compared to those who weren’t so frequent. Studies had
used a dose-response effect to observe the relationship between cannabis and
mental health. Most of the studies had included people that hadn’t had
psychosis at baseline as it showed the effect that cannabis had on their mental
health. The relationship between cannabis and mental health issues is complex.
Many people may use cannabis for its euphoric and relaxing effects, however
others may experience feelings such as depression and anxiety when intoxicated.
Hallucinations and psychotic symptoms may also be triggered by the use of
cannabis 

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