The Relationship between Alcohol/Cannabis Use and Symptom Profile and Progression in Individuals at Risk for Psychosis Open Access

Larson, Molly Kathleen (2011)

Permanent URL: https://etd.library.emory.edu/concern/etds/hq37vp29n?locale=en
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Abstract

Alcohol and cannabis are the most commonly used substances among persons with schizophrenia and other psychotic disorders and often associated with a poorer prognosis. Recent research indicates that better social functioning and fewer negative symptoms are associated with alcohol use early in the course of the illness, however, worse negative and positive symptoms are often found later. A mounting body of evidence suggests that cannabis use appears to confer increased risk of psychosis. Furthermore, research suggests that poorer outcome, including more hospitalizations and lower functioning scores, as well as worse positive symptoms and greater overall severity of illness is associated with cannabis dependence and abuse. There is a dearth of prospective studies examining the relation between alcohol and cannabis use in individuals designated as prodromal based on the presence of subclinical psychotic symptoms. Furthermore, there are no published reports on the independent and/or interactive effect of these substances.

The current study extends the literature by examining the association of symptom profile and progression with varying levels of alcohol and cannabis use in a putatively prodromal sample. Participants were recruited at eight study sites as part of the North American Prodrome Longitudinal Study. Participants with symptom and substance use data at baseline were examined for an association between current symptom severity and substance use. Participants with both baseline and six-month follow-up data were examined for the relation between substance use at baseline and symptom severity at follow-up. An interactive effect of these substances on symptom severity at baseline was found. Less severe negative symptoms are associated with moderate alcohol use and abstinence from cannabis. In contrast, those who report no alcohol use, or alcohol abuse/dependence and cannabis use, showed more severe negative symptoms. More severe positive symptoms are associated with increased levels of cannabis and alcohol use. No significant results were found for the association between substance use and symptom progression. These findings point to the importance of jointly examining the effects of substances that have a high rate of co-occurrence, in that interactive and independent effects are elucidated. The results are discussed in the context of potential mechanisms.

Table of Contents

Table of Contents

Introduction...1

The Prodrome to Schizophrenia and Other Psychotic Disorders...5

Substance Use in Schizophrenia and Other Psychotic Disorders...8

Prevalence and Incidence...8
The Relation of Substance Use with Symptom Profile and Course of Illness...12
Conclusions...20

Alcohol Use and Psychotic Disorders...21

Prevalence and Incidence...21
The Relation of Alcohol Use with Symptom Profile and Course of Illness...23
Potential Mechanisms...27
Conclusions...30

Cannabis Use and Psychotic Disorders...31

Prevalence and Incidence...31
The Relation of Cannabis Use with Psychosis Onset...33
The Relation of Cannabis Use with Symptom Profile and Course of Illness...34
Experimental Studies of the Effects of Cannabis (Δ9 THC) on Patients and Healthy Controls...40
Specificity of Cannabis Use to Schizophrenia...43
Potential Mechanisms: Cannabinoids and Dopamine...43
Diathesis-Stress and Adolescent Brain Development...46
Conclusions...49

Goals of the Present Study...50
Hypotheses...51
Method...53

Participants and Procedure...53
Measures...56

Results...57

Descriptive Statistics...57
Substance Use...61
Regression Analysis Results...62
Cross-sectional Analyses of Baseline Symptoms...62

Baseline negative symptoms...62
Baseline positive symptoms...65

Longitudinal Analyses of Follow-up Symptoms...66

Discussion...68

Substance Use and Baseline Negative Symptoms...69
Substance Use and Baseline Positive Symptoms...73
Follow-up Symptom Severity...77
Cannabis Use and Age...80
Potential Mechanisms...81

Alcohol...81
Cannabis...83

Limitations and Future Directions...85

Summary and Conclusions...88
References...90


Tables and Figures...109

Table 1. Alcohol and Cannabis Use of Subsample
Table 2. Alcohol Use and Cannabis Use of Participants with Follow-Up Data
Table 3. Results of Regression Analysis of Baseline Negative Symptom Ratings
Table 4. Results of Regression Analysis of Baseline Social Anhedonia Symptom Ratings
Table 5. Results of Regression Analysis of Baseline Positive Symptom Ratings
Table 6. Results of Regression Analysis of Follow-Up Negative Symptom Ratings
Table 7. Results of Regression Analysis of Follow-Up Positive Symptom Ratings
Table 8. Results of Regression Analysis of Follow-Up Positive Symptom Ratings and Age
Figure 1. Mean Baseline Negative Symptom Ratings across Levels of Alcohol and Cannabis Use
Figure 2. Mean Baseline Social Anhedonia Symptom Ratings across Levels of Alcohol and Cannabis Use
Figure 3. Mean Baseline Positive Symptom Ratings across Levels of Alcohol Use
Figure 4. Mean Baseline Positive Symptom Ratings across Levels of Cannabis Use

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