Cannabis use and psychotic-like experiences in two adolescent samples in Mexico City

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

a. Background


Cannabis use is the most used ‘illicit’ drug worldwide. Prevalence of use among adolescents in Mexico has increased significantly in the last decade (Villatoro et al., 2012). Research has shown that cannabis use during adolescence may have worse adverse effects than using cannabis later in life, such as poor mental health and cannabis dependence (Gorey, Kuhns, Smaragdi, Kroon, & Cousijn, 2019). Furthermore, there has been an increased interest in the association between high potency cannabis use and its impact on psychotic-like experiences. Research has shown that highly potent cannabis use is associated with psychotic disorders (Di Forti et al., 2014). Furthermore, this association may be stronger when onset of use occurs earlier in life.


b. Aim

To identify if cannabis use predicts the appearance of psychotic-like experiences in an adolescent student sample and an adolescent substance misuse clinical sample of mainly cannabis users in Mexico City aged 15 to 19 years old.


c. Hypotheses

Adolescent Student Sample (15 to 19 years old)
 
1. Lifetime cannabis use predicts the presence of psychotic-like experiences in an adolescent student sample in Mexico City and Estado de Mexico.
2. Frequent cannabis use predicts the presence of psychotic-like experiences in an adolescent student sample in Mexico City and Estado de Mexico.
3. Use of skunk-type cannabis vs. herbal-type cannabis predicts an increased presence of psychotic-like experiences in an adolescent student sample in Mexico City and Estado de Mexico.


Adolescent Substance Misuse Clinical Sample (13 to 21 years old)
 
1. Increased frequency of cannabis use predicts the presence of psychotic-like experiences in an adolescent substance misuse clinical sample in Mexico City and Estado de Mexico.
2. An earlier age of first cannabis use predicts an earlier age of onset of psychotic-like experiences in an adolescent substance misuse clinical sample in Mexico City and Estado de Mexico.
3. Skunk-type cannabis vs. herbal-type cannabis use predicts the presence of psychotic-like experiences in an adolescent substance misuse clinical sample in Mexico City and Estado de Mexico.


d. Methods

This is a cross-sectional study conducted to examine patterns of cannabis use and prevalence of psychotic-like experiences in two adolescent samples in Mexico City: an adolescent student sample, a total of 657 participants completed all the questionnaires (53% females, mean age 16.51) and an adolescent substance misuse clinical sample, a total of 121 participants completed all the questionnaires (14.8% females, mean age 16.56). Quantitative data was collected through questionnaires regarding cannabis use, psychotic-like experiences, use of other drugs and sociodemographic characteristics in both samples. Descriptive statistics, ANOVAS, chi-square, odds ratios, linear, logistic and multinomial logistic regression analyses were conducted.


e. Results
 
Results are summarised by sample to facilitate identification of specific outcomes. In the student sample, no statistically significant associations were found between different patterns of cannabis use and psychotic-like experiences. In the substance misuse clinical sample, initially, daily cannabis use and use of 2 or more joints, were significantly associated with higher mean scores in the total score of psychotic-like experiences questionnaire. However, associations were no longer statistically significant whilst controlling for demographics, tobacco and use of other illicit drugs. Lastly, a significant association was found between low potency herbal type-cannabis and psychotic-like experiences (OR=.24; 95%CI=.08--.73; p=0.011) in the adolescent substance misuse clinical sample.


f. Conclusions
 
Overall, results from the present study are unexpected, as emerging research has shown that high potency cannabis use is associated with psychotic experiences. Although a significant association was found between herbal-type cannabis and psychotic-like experiences in the substance misuse clinical sample, this is opposite to what previous research has shown. This study has important clinical, educational and policy implications for cannabis use in adolescence.
Date of Award1 Dec 2020
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorMichael Lynskey (Supervisor) & Clare Mackie (Supervisor)

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