Journal Club
Alcohol, Other Drugs, and Health: Current Evidence
July–August 2016
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Featured Article
Cannabis use and risk of psychiatric
disorders: prospective evidence
from a US national longitudinal
study
Blanco C, et al. JAMA Psychiatry. 2016;73(4):388–395.
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2
Study Objective
• To examine the prospective associations
between cannabis use and substance use
disorder (SUD) among adults, and mood
and anxiety disorders at 3 year follow-up.
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3
Study Design
• Prospective survey of 34,653 US adults from two waves of
the National Epidemiologic Survey on Alcohol and Related
Conditions (NESARC).
– Wave 2 was interviewed approximately 3 years after wave 1.
• Researchers used multivariable logistic analysis and
propensity score matching.
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4
Assessing Validity of an
Article about Prognosis
• Are the results valid?
• What are the results?
• How can I apply the results to patient
care?
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5
Are the Results Valid?
• Was the sample representative?
• Were the subjects sufficiently homogeneous with
respect to prognostic risk?
• Was follow-up sufficiently complete?
• Were objective and unbiased outcome criteria
used?
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Was the sample representative?
All subjects in this study…
• were a nationally representative cohort of US adults
(N=34,563)
• 14,564 were male; mean age 45 years
• “Black and Hispanic individuals and young adults
(aged 18-24 years) were oversampled, with data
adjusted for oversampling and household- and personlevel nonresponse”
• 1279 of participants in wave 1 had cannabis use
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Were the subjects sufficiently
homogeneous with respect to prognostic
risk?
• Yes.
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8
Was follow-up
sufficiently complete?
•
•
Yes. 81.5% (n = 34 653) of participants
interviewed in wave 1 were interviewed for
wave 2.
Researchers developed sample weights to
adjust for non-response in wave 2.
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Were objective and unbiased
outcome criteria used?
• Yes.
– Primary outcome development of a mood,
anxiety, and substance use disorder using the
Alcohol Use Disorder and Associated Disabilities
Interview Schedule (AUDADIS-IV)
– It is not stated whether this assessment was
blinded to knowledge of cannabis exposure
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What Are the Results?
• How likely are the outcomes over time?
• How precise are the estimates of
likelihood?
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How likely are the outcomes over time?
• In adjusted analyses, cannabis use was
associated with an increased prevalence and
incidence of SUD (odds ratio [OR], 6.2), but
not mood (OR, 1.1) and anxiety disorders
(OR, 0.9).
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How precise are the estimates
of likelihood?
• Cannabis use was associated with:
– alcohol use disorder (prevalence: OR, 2.5; incidence:
OR, 2.7; 95% CI, 1.9-3.8)
– cannabis use disorder (prevalence: OR, 12.4;
incidence: OR, 9.5; 95% CI, 6.4-14.1)
– other drug use disorder (prevalence: OR, 3.1;
incidence: OR, 2.6; 95% CI, 1.6-4.4)
– nicotine dependence (prevalence: OR, 1.5; incidence:
OR, 1.7; 95% CI, 1.2-2.4).
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How Can I Apply the Results
to Patient Care?
• Were the study patients and their management
similar to those in my practice?
• Was follow-up sufficiently long?
• Can I use the results in the management of
patients in my practice?
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Were the study patients similar
to those in my practice?
• The study population was large and nationally
representative, although the sample is
household and not clinically-based
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15
Was follow-up sufficiently long?
• Likely not. The patients were followed 3 years
after initial interviews. Given the adult sample
and the time course for the emergence of
mood and anxiety disorders, there may not
have been sufficient time for the development
of such conditions.
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Can I use the results in the
management of patients in my practice?
• Yes. Cannabis use appears to be associated
with increased risk for alcohol, cannabis,
nicotine, and other drug use disorders. This
can inform screening and prevention
interventions.
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