Available online at:
https://cc.arcabc.ca/islandora/object/cc%3Apsycjournal

J Camosun Psyc Res. (2024). Vol. 6(1), pp. 1-7.
Submitted Summer 2023; accepted May 2024.

Cannabis Use Disorder as a Factor for Schizophrenia
Development.
Authors: Amy M. Carrier*
Supervising Instructor: Cate Pelling, Psyc 250 (“Psychopathology”)
Department of Psychology, Camosun College, 3100 Foul Bay Road, Victoria, BC, Canada V8P 5J2
*Corresponding author email: amycarrier22@gmail.com

ABSTRACT
This article investigated the relationship between cannabis use disorder and schizophrenia
which are both problematic disorders recognized in the DSM-5TR. Frequent consumption of
cannabis including tetrahydrocannabinol (THC), may cause paranoia that associates with
delusions or hallucinations in some individuals. Schizophrenia may involve symptoms that
disrupt an individual’s daily functioning. Though the DSM-5TR recognizes cannabis-induced
psychotic disorders, research on whether cannabis use disorder itself may cause schizophrenia
remains inconsistent. Two studies investigated population using cannabis, as well as individuals
diagnosed with cannabis use disorder. Six articles investigated interactions involving cannabis
use disorder and schizophrenia. Interactions of biological (COMT enzyme, dopamine
dysregulation, and endocannabinoid systems), psychological (emotional dysregulation), social
(attachment styles) factors may influence early cannabis consumption. Cannabis consumption
that develops into cannabis use disorder may contribute to higher risk of developing
schizophrenia at an earlier age for individuals already susceptible to the disorder. Finding
existing interactions between cannabis use disorder and schizophrenia may reduce harm in
individuals vulnerable to both disorders.
1. Introduction
The aim of this research paper is to
explore the relationship between cannabis
use disorder and schizophrenia. At times,
cannabis is known to cause paranoia that
also associates with delusions or
hallucinations (Wright et al., 2021). Whether
the relationship is causational remains
controversial. If cannabis is an individual
variable that causes schizophrenia or a link
between each psychological disorder
connects due to pre-existing vulnerabilities
will further be investigated.

Cannabis is the dried flower buds and
leaves of a hemp plant that can be smoked or
ingested for both medical and non-medical
purposes. This study will focus on
individuals who consume cannabis with
tetrahydrocannabinol (THC) included, the
main psychoactive compound found in
cannabis. Cannabis used for non-medical
purposes will also be the primary focus and
can be defined as consumption for social
enjoyment, pleasure, cultural or spiritual
reasons, other non-medical purposes.
Though cannabis is recognized as a
hallucinogen, the substance may cause
depressant and stimulant effects (Barlow et
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al., 2021). The DSM-5 recognizes cannabis
use disorder as “a problematic pattern of
cannabis use leading to clinically significant
impairment or distress” (American
Psychiatric Association, 2013) and an
individual must meet at least two of 11
criteria for a 12-month period specified in
the diagnostic manual.
Schizophrenia is a complex psychological
disorder that may involve delusions,
auditory or visual hallucinations,
disorganized speech, other symptoms that
disrupt an individual’s daily functioning
(Barlow et al., 2021). Though causes of
schizophrenia involve biological,
psychological, social factors, a series of
research assessments and the DSM-5TR
recognizes cannabis-induced psychotic
disorders. Health Canada (2022) also warns
“regular use of cannabis can increase the
risk of psychosis and schizophrenia and
higher THC content can lower the age of
onset of schizophrenia,” but only 29% of
Canadians who consumed cannabis reported
seeing following warning labels on cannabis
products in 2021 (Government of Canada,
2022). This may exemplify why many
individuals consuming cannabis are unaware
or misunderstand the connection between
cannabis and psychopathology.
The purpose of finding any existing links
between cannabis use disorder and
schizophrenia is to reduce harm in
individuals vulnerable to both disorders.
Further research may also protect those
vulnerable to psychological distress that may
have resulted from cannabis consumption.

To further define cannabis use disorder,
this paper sought to understand the
population of cannabis consumers. It was
discovered that individuals who began
experimenting with cannabis at younger
ages such as the ages between 11 to 18,
developed greater risk for developing
cannabis use disorder (Clements-Noelle et
al., 2022). Childhood trauma such as abuse
and neglect, sexual abuse, negative family
communication, conflict within families,
influenced early onset of cannabis
consumption (Clements-Noelle et al., 2022).
Early onset of cannabis consumption
combined with childhood trauma, led to an
increased risk for developing cannabis use
disorder as adolescents (Clements-Noelle et
al., 2022).

2. Literature Review

2.2 Cannabis Use Disorder as a
Schizophrenia Factor

2.1.2 Meta-analysis 2
Childhood trauma, chronic stress, major
life events, associated with cannabis use in
adult individuals (Nia et al., 2023).
Childhood trauma was also measured using
the Childhood Trauma Questionnaire.
Chronic stress had the least influence on
cannabis consumption, as childhood trauma
and cannabis consumption showed greater
correlation. A biological finding suggested
that endocannabinoid system dysregulation
disrupted with trauma exposed individuals
who then showed greater rates of cannabis
use (Nia et al., 2023). It was also found
childhood trauma associated with women
more than men who consumed cannabis
(Nia et al., 2023).

2.1 Population Using Cannabis
2.2.1 Meta-analysis 1
2.1.1 Meta-analysis 1
Pearson and Berry (2019) discovered
high-intoxication levels in individuals who
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consumed cannabis and experienced
psychotic episodes reported a plan to quit
cannabis consumption, exemplifying the
significant distress cannabis caused in
individuals. Those who consumed cannabis
daily from a young age and used higher
potency cannabis experienced psychotic
symptoms such as delusions and
hallucinations earlier than individuals
diagnosed with schizophrenia but did not
consume cannabis (Pearson & Berry, 2019).
A controlled case study discovered within
individuals who had cannabis use disorder
and converted to cannabis-induced psychotic
disorder, 47.4% then converted to
schizophrenia (Pearson & Berry, 2019).
Furthermore, cannabis seemed to interact
with the catechol-O-methyltransferase
(COMT) enzyme, an important genotype in
the breakdown of dopamine in the prefrontal
cortex. A dysregulation of dopamine was
found to be a critical pathophysiology aspect
of schizophrenia (Pearson & Berry, 2019).
2.2.2 Meta-analysis 2
Research aimed to find evidence in
cannabis increasing risk of development for
schizophrenia and other psychotic disorders.
Many articles however, concluded it is
unclear whether schizophrenia emerged after
or before cannabis consumption (Allebeck et
al., 2023). This article discovered
individuals who consumed cannabis had a
mean age onset of schizophrenia of 23.4
years and individuals who did not consume
cannabis had a mean age of 27.7 years
(Allebeck et al., 2023). These results suggest
that cannabis use influenced earlier onset of
schizophrenia.
2.2.3 Meta-analysis 3
Investigating the relationship between
cannabis use disorder and schizophrenia,

findings discovered “young males might be
particularly susceptible to the effects of
cannabis on schizophrenia” (Hjorthoj et al.,
2023). It was discovered detection and
treatment of cannabis use disorder was
especially crucial for 16–25-year-old
individuals. One-fifth of schizophrenia cases
could be prevented by averting cannabis use
disorder in males (Hjorthoj et al., 2023).
Evidence suggested females seemed to be at
lower risk than males, demonstrating
different biological factors. High THC
concentration as well as frequent cannabis
use was found to impact early onset of
psychosis and schizophrenia compared to
individuals who did not consume cannabis.
2.2.4 Meta-analysis 4
The results of longitudinal imaging
genetics study of schizophrenia predicted
future onset of cannabis use (Elkrief et al.,
2021). Individuals take polygenic risk scores
to discover several genetic variants and risks
of developing certain diseases. This paper
investigated if any causation for cannabis
consumption and schizophrenia existed.
Though cannabis use remained a risk factor
for psychotic-like symptoms and
schizophrenia, causality was not found.
Instead, evidence showed that individuals
with future onset of schizophrenia had an
earlier onset of their disorder with cannabis
use (Elkrief et al., 2021). Because polygenic
risk scores involve limitations, portions of
genetic effects such as rare variants and
copy number variants were not captured and
that contributes to the pathogenesis of
schizophrenia (Elkrief et al., 2021). Further
reports suggested social factors may
contribute to the onset of early onset
schizophrenia, and genetic predispositions
should not be the primary focus (Elkrief et
al., 2021).
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2.2.5 Meta-analysis 5
The relationship between cannabis use
and schizophrenia were investigated. Three
hypotheses asked whether “cannabis can
trigger schizophrenia, cannabis is used to
mitigate symptoms of schizophrenia, there
are common factors which might account for
the association” (Hamilton & Monaghan,
2019).
Though biological evidence is most
investigated, social, and psychological
factors such as environments, family history,
childhood, thinking styles, behaviour,
should also be enquired. It was discovered
childhood trauma to be a significant factor
towards the development of psychotic
disorders (Hamilton & Monaghan, 2019).
Findings suggested individuals with a
predisposition to schizophrenia who
consumed high doses of cannabis frequently
induced early onset of schizophrenia.
However, few individuals also became at
risk for developing psychosis and
schizophrenia even after low exposure levels
to cannabis (Hamilton & Monaghan, 2019).
Evidence also concluded consequences of
cannabis and schizophrenia are apparent in
research drawn from North America and
Europe. When different locations like Asia
are researched, it is revealed there are less
cases of cannabis-induced psychotic
disorders because there is lower population
use of cannabis in Asian countries
(Hamilton & Monaghan, 2019). Further
limitations of this research include the
failure to study cannabis use and
schizophrenia involving females. Though
evidence suggests a combination of
biological, social, psychological factors
contributed to the onset of cannabis induced
schizophrenia and males, the female sex was
left out. Females would also need to be
researched to gain a better understanding on

the biological aspects of cannabis use and
schizophrenia.
2.2.6 Meta-analysis 6
Differentiating from other research where
heavy and frequent cannabis consumption
was a factor for early onset of schizophrenia,
Ho and others investigated low dosage of
cannabis could contribute to risk of
schizophrenia. Using cognitive assessments,
infrequent cannabis consumption with lower
THC dosages still disrupted cognitive
maturation (Ho et al., 2022). Newer ways of
using cannabis in forms of oils, edibles,
liquids, vaping have proven to contain
higher THC concentrations of up to 80%
increased from smoking cannabis (Ho et al.,
2022). As higher THC concentration with
frequent use was found to increase risk of
early onset of schizophrenia, new ways of
smoking or ingesting cannabis remains a
concern (Ho et al., 2022).
2.3 Further Findings
Results from all findings suggest
cannabis use disorder may contribute to
early onset of schizophrenia in individuals
with pre-existing vulnerabilities. Biological
factors such as the interaction between the
COMT genotype and dopamine in the
prefrontal cortex, higher THC concentration,
male and female sex, endocannabinoid
system dysregulation, played a role in the
onset of developing cannabis use disorder
and schizophrenia. Trauma exposure and
attachment styles have shown to create risk
for both harmful patterns of cannabis use
and schizophrenia (Carley & Adams, 2023).
Further findings discovered in young
adults suggest cannabis use often associate
with depression or anxiety (Wright et al.,
2021). Other influences such as age and sex
also contributed to development of cannabis
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use disorder. High schizophrenia
vulnerability was related to a stronger
increase in cannabis use after age 16
(Hiemstra et al., 2018). In individuals with
schizophrenia who consume cannabis,
“auditory hallucinations and delusions of
reference associated more among females.”
(Wainberg et al., 2021). Among individuals
who experienced delusions and
hallucinations, 21% of individuals reported
symptoms usually lasted longer than four
weeks (Schoeler et al., 2022).
Research on cannabis use disorder and
the relationships it has with other
psychological disorders is important in
protecting vulnerable individuals. It was
found that the incidence of early onset
schizophrenia could be reduced by
approximately 8% if there was elimination
of frequent cannabis use (Arseneault et al.,
2018).
3. Conceptualization
To conceptualize why cannabis use
disorder and schizophrenia may have a
relationship, the bio-psycho-social model
was initially investigated. Biologically,
children with schizophrenic parents are
vulnerable to the disorder, and multiple gene
variances produce vulnerabilities. However,
findings suggest interaction of cannabis and
pre-existing vulnerability to schizophrenia
may make symptoms of schizophrenia
emerge earlier (Hamilton & Monaghan,
2019). Biological factors include
involvement of the COMT enzyme and
dopamine dysregulation involving
schizophrenia. This may be a critical piece
in the early onset of schizophrenia with
patients who have cannabis use disorder.
Furthermore, endocannabinoid system
dysregulation also interferes with the
combination of cannabis and schizophrenia
(Nia et al., 2023).

Psychological factors are noted by the
individuals diagnosed with cannabis use
disorder. Most individuals who experienced
childhood abuse in forms of abuse and
neglect, developed dependency and met
criteria for a DSM-5 diagnosis of cannabis
use disorder. Findings also suggest the
relationship between cannabis use disorder
with other existing psychological disorders
such as anxiety and depressive disorders
(Wright et al., 2021). Emotional
dysregulation from childhood may create
low self-esteem and other negative thinking
patterns that play a part in early onset of
cannabis consumption. Because cannabis is
oftentimes publicized to create positive
sensations in individuals, those vulnerable to
psychological disorders or have low selfesteem may view cannabis as a substance
that can neutralize negative emotions. Most
individuals who consume cannabis from
young ages, go on to develop cannabis use
disorder due to the long going relationship
with the substance (Clements-Noelle et al.,
2022).
Furthermore, social factors and different
traumas such as rejecting natures from
caregivers can create avoidant or anxious
attachment styles in children. This may also
influence early interaction with substances
like cannabis, and individuals may easily
form a problematic pattern of cannabis
consumption that later forms into cannabis
use disorder. The vulnerabilities that are preexistent within individuals who have
cannabis use disorder may not combine well
with predisposition to schizophrenia and the
disorder itself.
4. Conclusion
In conclusion, cannabis itself is not
capable of causing schizophrenia, but those
who use cannabis on a regular basis or have
cannabis use disorder and are susceptible to
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schizophrenia are at higher risk for
developing the disorder at an earlier age.
The younger the age of substance
consumption combined with heavy doses,
the higher risk of developing cannabis use
disorder. Childhood trauma such as abuse
and neglect may influence early onset of
cannabis consumption.
4.1 Directions for Future Research
As cannabis has two subtypes, whether
sativa or indica produce different results
should be investigated. It is unknown
whether different cannabis strains such
sativa and indica produce different results.
Sativa is advertised to reduce anxiety or
stress and increase creativity, whereas indica
is known to reduce insomnia and increase
relaxation. Whether these differences cause
different effects in individuals vulnerable to
schizophrenia and other psychotic disorders
is not yet understood.
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