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RESEARCH ARTICLE
Cannabis use among U.S. military veterans with
subthreshold or threshold posttraumatic stress disorder:
Psychiatric comorbidities, functioning, and strategies for
coping with posttraumatic stress symptoms
Melanie L. Hill1,2Mallory Loflin1Brandon Nichter1Peter J. Na3,4
Sarah Herzog5,6Sonya B. Norman1,2,7,8Robert H. Pietrzak3,9,10
Department of Psychiatry, University of California, San Diego, California, USA
VA San Diego Healthcare System, San Diego, California, USA
Department of Psychiatry, Yale School of Medicine, New Haven, Connecticut, USA
VA Connecticut Healthcare System, West Haven, Connecticut, USA
Department of Psychiatry, Columbia University Irving Medical Center, Columbia University, New York, New York, USA
Division of Molecular Imaging and Neuropathology, New York State Psychiatric Institute, New York, New York, USA
National Center for PTSD, White River Junction, Vermont, USA
VA Center of Excellence for Stress and Mental Health, San Diego, California, USA
National Center for PTSD, VA Connecticut Healthcare System, West Haven, Connecticut, USA
Department of Social and Behavioral Sciences, Yale School of Public Health, New Haven, Connecticut, USA
Correspondence
Melanie Hill, VA San Diego Healthcare
System, La Jolla Village Dr., San
Diego, CA, , USA.
Email: mlhill@asu.edu
This article has been contributed to by
U.S. Government employees and their
work is in the public domain in the USA.
Abstract
Cannabis use is common among individuals with posttraumatic stress disorder
(PTSD) symptoms, but its impact on psychiatric symptoms and functioning in
this population is unclear. To clarify the clinical and functional correlates of
cannabis use in individuals with PTSD symptoms, we analyzed data from the
– National Health and Resilience in Veterans Study, a nationally repre-
sentative survey of U.S. military veterans. Participants with current subthreshold
or full PTSD (N=) reported on their past--month cannabis use and cur-
rent psychiatric symptoms, functioning, treatment utilization, and PTSD symp-
tom management strategies. Veterans with subthreshold/full PTSD who used
cannabis more than weekly were more likely to screen positive for co-occurring
depression, anxiety, and suicidal ideation than those who did not use cannabis,
ORs =.–., or used cannabis less than weekly, ORs=.–.. Veterans who
used cannabis more than weekly also scored lower in cognitive functioning than
veterans with no use, d=., or infrequent use, d=., and were substan-
tially more likely to endorse avoidance coping strategies, ORs=.–., includ-
ing substance use, OR =., and behavioral disengagement, ORs=.–., to
manage PTSD symptoms. Despite more psychiatric and functional problems,
J. Trauma. Stress. ;–. wileyonlinelibrary.com/journal/jts © International Society for Traumatic Stress Studies 1
2HILL .
veterans with frequent cannabis use were not more likely to engage in mental
health treatment, ORs=.–.. The results suggest enhanced cannabis use
screening, interventions targeting risky use, and strategies promoting treatment
engagement may help ameliorate more severe clinical presentations associated
with frequent cannabis use among veterans with subthreshold/full PTSD.
More than half of U.S. states include posttraumatic stress
disorder (PTSD) as a qualifying condition for accessing
medical cannabis despite a lack of evidence that cannabis
is an efficacious treatment for the disorder (Stanciu et al.,
). Although several recent studies have investigated
the association between whole-plant cannabis use and
PTSD symptoms (e.g., Bonn-Miller et al., , ;
LaFrance et al., ; Metrik et al., ), results have been
mixed, and the effects of cannabis on the clinical presen-
tation of PTSD remain unclear. In particular, there is a
dearth of research on the association between cannabis
use and indices of distress and functioning in individuals
with PTSD symptoms. This represents an important gap in
knowledge, as PTSD is associated with psychosocial diffi-
culties (Bovin et al., ); impairment in cognitive, emo-
tional, and physical functioning (McCarthy et al., );
and comorbidity with other psychiatric disorders (Wisco
et al., ).
Importantly, trauma-related symptoms that meet some,
but not all, of the PTSD criteria outlined in the Diagnostic
and Statistical Manual of Mental Disorders (fifth ed.; DSM-
5; American Psychiatric Association, ; i.e., subthresh-
old PTSD), have also been associated with considerable
functional impairment (Mota et al., ), and individuals
with subthreshold and threshold PTSD have higher rates of
suicidal behaviors as well as mood, anxiety, and substance
use disorders (SUDs) than individuals with less severe
or no PTSD symptoms (McLaughlin et al., ; Mota
et al., ; Wisco et al., ). In addition, co-occurring
SUDs have been associated with further elevations in the
functional burden of PTSD (Simpson et al., ). One
interpretation of this finding is that trauma-exposed
individuals may use substances to avoid or escape
traumatic stress symptoms, such as intrusive memories,
anhedonia, or negative affect, which contributes to the per-
sistence of PTSD symptoms and prevents functional recov-
ery (Palmisano et al., ).
Despite increased access to cannabis due to state-driven
legalization, scarce research has examined associations
between cannabis use and factors related to functioning
and recovery in individuals with PTSD symptoms. This
is important to clarify, as cannabis use is linked to men-
tal health difficulties and impaired functioning in the
general population (Hasin, ). To date, some studies
focusing on cannabis use disorder (CUD) have found that
among individuals receiving treatment for PTSD, those
with CUD have poorer outcomes than those without CUD
(Bedard-Gilligan et al., ; Bonn-Miller et al., ;
Wilkinson et al., ), and CUD is associated with slower
improvement in PTSD symptoms over time (Livingston
et al., ). Nevertheless, the impact of frequent cannabis
use, with or without a diagnosis of CUD, on psychiatric and
functional variables is unclear. To date, the only random-
ized controlled trial (RCT) on the efficacy of whole-plant
cannabis to treat PTSD found a null effect of cannabis com-
pared with placebo on psychiatric (e.g., depressive and anx-
iety symptoms) and functional outcomes (e.g., psychoso-
cial difficulties; Bonn-Miller et al., ). However, a recent
observational study of Canadian adults found an attenu-
ated association between PTSD and symptoms of depres-
sion and suicidal ideation (SI) among individuals who used
cannabis (Lake et al., ).
Given these mixed findings, additional studies in large-
scale, population-based samples are needed. One high-risk
subpopulation for which the association between cannabis
use and PTSD-related functioning is especially relevant is
U.S. military veterans. Veterans have high rates of trauma
exposure and PTSD (Wisco et al., )andaremorethan
twice as likely as civilians to report medical cannabis use
(Davis et al., ). Nationally representative studies have
found that cannabis use is associated with elevated odds of
PTSD among veterans (Browne et al., ), and nearly in
veterans with PTSD reported recent cannabis use in –
(Hill, Loflin, et al., ). Although previous stud-
ies of Veterans Health Administration (VHA) data have
found that PTSD–CUD comorbidity is associated with an
increased risk of other co-occurring conditions (e.g., Bryan
et al., ), less than % of veterans use VHA services as
their primary source of health care, and veterans served by
VHA have higher rates of psychiatric problems than vet-
erans who use non-VHA health care (Meffert et al., ).
Thus, it remains unclear whether these findings extend to
veterans with subthreshold or threshold PTSD in the gen-
eral population.
To address these gaps in knowledge, we analyzed data
from a contemporary, nationally representative sample
of U.S. military veterans to examine differences in treat-
ment utilization, psychiatric comorbidities, functioning,
and trauma-related coping strategies among veterans with
subthreshold or threshold PTSD and three levels of recent
CANNABIS USE IN VETERANS WITH PTSD SYMPTOMS 3
cannabis use: no use, less than weekly use, and more than
weekly use. Based on findings from studies in the vet-
eran population (Hill, Nichter, Norman, et al., )and
among veterans with PTSD and substance use problems
(Bryan et al., ; Boden et al., ), we hypothesized that
veterans with subthreshold or threshold PTSD who used
cannabis frequently (i.e., more than once a week) would
(a) be more likely than those who did not use cannabis
to screen positive for co-occurring psychiatric conditions
and be engaged in mental health treatment, (b) score
higher on measures of functional impairment, and (c) be
more likely to use avoidance strategies to cope with PTSD
symptoms.
METHOD
Participants and procedure
Data were analyzed from the – National Health
and Resilience in Veterans Study (NHRVS), which sur-
veyed a nationally representative sample of , U.S.
military veterans. The sample included all military
branches, and participants completed an anonymous web-
based survey. The recruitment and sampling methodol-
ogy for the NHRVS has been published previously (Hill,
Nichter, Loflin, et al., ). The sample was drawn from
KnowledgePanel R
, a probability-based, online, nonvol-
unteer access survey panel of U.S. adults maintained by
the research firm Ipsos. KnowledgePanel R
members were
recruited by phone and mail through national random
samples, using dual sampling frames that include house-
holds with and without listed telephone numbers and
internet access, as well as cell-phone-only households. To
permit generalizability of the study results to the U.S. vet-
eran population, the Ipsos statistical team computed post-
stratification weights using benchmark distributions from
the Veterans Supplement of the most recent Current Pop-
ulation Survey (Bureau of the Census, ). All partici-
pants provided written informed consent. The study was
approved by the Human Subjects Committee of the VA
Connecticut Healthcare System and carried out in accor-
dance with the Declaration of Helsinki.
Measures
Sociodemographic and military variables
Data captured in the NHRVS included age, sex (male,
female), race and ethnicity (White, non-White), educa-
tional attainment (some college or higher education, up to
high school diploma), annual household income ($,
(USD) or more, less than $,), marital status (married
or living with partner, not married or living with partner),
retirement status (retired, not retired), primary source of
health care (VHA, other), enlistment status (enlisted ver-
sus drafted or commissioned), and combat exposure status
(yes, no).
PTSD symptoms
Veterans completed the PTSD Checklist for DSM-5 (PCL-
; Weathers, Litz, et al., ), reporting on PTSD symp-
toms in relation to their self-reported “worst” Criterion A
traumatic event, as established on the Life Events Check-
list for DSM-5 (LEC-; Weathers, Blake, et al., ). The
PCL- is a -item measure of past-month DSM-5 PTSD
symptoms, with responses ranging from (notatall)to
(extremely). Higher scores indicate more severe symptoms.
Additional questions were added to assess Criteria F (i.e.,
symptom duration) and G (i.e., functional significance).
Veterans screened positive for subthreshold PTSD if they
endorsed exposure to a Criterion A event and (a) met two
or three of the other criteria (i.e., some combination of
one Criterion B symptom, one Criterion C symptom, two
Criterion D symptoms, or two Criterion E symptoms) at a
severity of (moderately) or higher or (b) all symptom B–
E criteria (i.e., one symptom each from Criteria B and C
and two symptoms each from Criteria D and E) but not -
month symptom duration and/or functional impairment.
Individuals screened positive for threshold PTSD if they
endorsed Criteria A–G for PTSD using the diagnostic algo-
rithm. Because veterans with more severe PTSD symptoms
may be more likely to use cannabis to cope, veterans’ con-
tinuous total scores on the past-month PCL- were also
considered as a covariate to determine whether cannabis
use was associated with outcomes over-and-above PTSD
symptom severity. In the present sample, Cronbach’s alpha
was ..
Cannabis use
Veterans reported on their recent (i.e., past months)
cannabis use by first responding “yes” or “no” to the
question: “Have you used any cannabis (i.e., marijuana,
hashish, tetrahydrocannabinol [THC], pot, grass, weed,
reefer) over the past months?” Among veterans who
endorsed any cannabis use in the past months, the
frequency of cannabis use was assessed using Item of
the Cannabis Use Disorder Identification Test–Revised
(CUDIT-R; Adamson et al., ), which asks participants
how often they used cannabis, with response options rang-
ing from (never)to(4 or more times a week) in the past
months. Based on this frequency measure, veterans were
classified into the following three categories: no cannabis
4HILL .
use, comprising veterans who denied any cannabis use in
the past months; less than weekly cannabis use, which
included veterans who endorsed on CUDIT-R Item
(monthly or less)or(2–4 times a month); and more than
weekly cannabis use, comprising veterans who endorsed
(2–3 times a week) or higher on CUDIT-R Item .
Adverse childhood experiences
Childhood trauma was assessed using the Adverse Child-
hood Experiences Questionnaire (ACEQ; Finkelhor et al.,
), a -item scale that assesses exposure to a range
of adversities that occurred before years of age. Scores
represent a count of the number of adversities endorsed
(range: –), with higher scores indicating more adverse
childhood experiences.
Lifetime trauma exposure
The LEC- (Weathers, Blake, et al., ) was used to assess
lifetime exposure to types of traumatic events. The num-
ber of lifetime traumatic experiences represented a count
of the number of events endorsed across the lifetime (i.e.,
events which veterans marked as “happened to me,” “wit-
nessed,” “learned about,” or “part of my job”).
Military sexual trauma
Veterans were asked to respond “yes” or “no” to two ques-
tions about experiences of sexual harassment and assault
during military service. Participants who answered “yes”
to either question were coded positive for military sexual
trauma.
Medical conditions
A count of medical conditions was obtained by summing
the number of medical conditions endorsed in response to
the question: “Has a doctor or healthcare professional ever
told you that you have any of the following medical condi-
tions?” (e.g., arthritis, cancer, diabetes; range: –).
Lifetime alcohol use disorder
Participants were considered to meet the DSM-5 diagnos-
tic criteria for alcohol use disorders with the endorsement
of two or more symptoms on the Mini-International Neu-
ropsychiatric Interview (M.I.N.I.; Sheehan et al., ),
which was adapted to be administered as part of the online
survey. Veterans reported “yes” or “no” to DSM-5 symp-
toms experienced during the past months. In the present
sample, Cronbach’s alpha was ..
Past-year alcohol consumption
The three-item Alcohol Use Disorders Identification Test–
Concise (AUDIT-C; Bush et al., ) was used to assess
past-year alcohol use. Items are related to the quantity and
frequency of alcohol consumption in the past year, with
responses scored on a Likert scale ranging from to . Pos-
sible scores range from to , with higher scores indicat-
ing higher degrees of alcohol consumption. Scores of or
higher for men and or higher for women are considered
positive for hazardous drinking or active alcohol use disor-
ders (Bush et al., ). In the present sample, Cronbach’s
alpha was ..
Lifetime nicotine dependence
The Fagerström Test for Nicotine Dependence (FTND;
Heatherton et al., ), a six-item measure of smoking
behaviors, was used to assess nicotine dependence. Items
have either Likert-type scale response options or “yes” or
“no” options. Scores of or higher on the FTND are con-
sistent with medium-to-high nicotine dependence. For the
present study, scores of or higher were coded as positive
for nicotine dependence.
Treatment utilization
Veterans responded “yes” or “no” to two questions about
their current engagement in psychosocial and pharmaco-
logical mental health treatments (i.e., “Are you currently
receiving psychotherapy or counseling for a psychiatric or
emotional problem?” and “Are you currently taking pre-
scription medication for a psychiatric or emotional prob-
lem?”). Veterans who answered “yes” to either question
were coded positive for current treatment engagement.
Depression and anxiety
The four-item Patient Health Questionnaire (PHQ-;
Kroenkeetal.,) was used to assess past--week
depressive and anxiety symptoms. Items related to symp-
tom frequency are rated on a Likert scale ranging from
(notatall)to(every day), with higher scores indicat-
ing more frequent symptoms. A positive screen for major
depressive disorder (MDD) was defined as a total score of
or higher on the two items comprising the MDD subscale
CANNABIS USE IN VETERANS WITH PTSD SYMPTOMS 5
(range: –). A positive screen for generalized anxiety dis-
order (GAD) was defined as a score of or higher on the
two-item GAD subscale (range: –). In the present sam-
ple, Cronbach’s alpha values for the MDD and GAD sub-
scales were . and ., respectively.
SI
An item on the longer nine-item PHQ (PHQ-; Kroenke
& Spitzer, ) related to SI was split into two separate
questions to assess current (i.e., past weeks) passive and
active SI (Thompson et al., ). Veterans who endorsed
either item (“Thoughts that you might be better off dead”
or “Thoughts of hurting yourself in some way”) screened
positive for SI.
Cognitive functioning
A continuous score on the six-item Medical Outcomes
Study (MOS) Cognitive Functioning Scale (Stewart et al.,
) was used to assess cognitive functioning. Participants
were asked to rate items related to the frequency of per-
ceived cognitive problems in the past month on a scale of
(none of the time) to (all of the time). The MOS uses
norm-based scoring to yield – scores based on norma-
tive data such that is the population mean, differences
of points represent a difference of standard deviation,
and higher scores indicate better cognitive functioning. In
the present sample, Cronbach’s alpha was ..
Physical and mental functioning
Continuous scores on the four physical functioning items
and the four mental functioning items from the Short
Form– Health Survey (SF-; Ware et al., )wereused
to assess physical and mental functioning, respectively.
Responses on SF- items range from (very poor)to
(excellent). Like the MOS, the SF- physical and mental
subscales use norm-based scoring such that scores on each
subscale range from to , with higher scores indicat-
ing better functioning. In the present sample, Cronbach’s
alpha was . for physical functioning and . for mental
functioning.
Psychological difficulties
The seven-item Brief Inventory of Psychosocial Function-
ing (B-IPF; Kleiman et al., ), an abridged version of the
-item Inventory of Psychosocial Functioning (IPF; Bovin
et al., ), was used to measure the severity of past--day
psychosocial difficulties. Response options ranged from
(none)to(extreme), and respondents only answered ques-
tions pertaining to domains that were relevant in the past
days (e.g., work, parenting). The B-IPF total score is
calculated by summing the scale items completed by the
respondent, dividing by the maximum possible score based
upon the number of applicable items, and multiplying by
. B-IPF total scores thus range from to and repre-
sent an index of overall psychosocial difficulties (i.e., more
problems with relationships, work, or school), with higher
scores indicating a higher degree of psychosocial difficul-
ties. In the present sample, Cronbach’s alpha was ..
PTSD coping strategies
As in previous NHRVS studies (e.g., Straus et al., ),
veterans were asked to rank three out of coping strate-
gies (see Table ) from the Brief COPE instrument (Carver,
) that they “most commonly use” to deal with symp-
toms related to their LEC-–identified most distressing
traumatic event (Weathers, Blake, et al., ). Based on
prior research that has identified a three-factor structure
for the Brief COPE (Wang et al., ), the coping
strategies were categorized into three coping styles for
the current study: self-sufficient coping (i.e., autonomous
problem- and emotion-focused strategies), socially sup-
ported coping (i.e., help-seeking strategies), and avoidant
coping (i.e., disengagement-based strategies).
Data analysis
Statistical analyses were performed using SPSS (Version
) statistical software. Raw unweighted frequencies are
reported, and poststratification sampling weights were
applied when computing prevalence and inferential statis-
tics (Ipsos, ). First, descriptive statistics were com-
puted to characterize the prevalence of less than weekly
and more than weekly cannabis use. Second, univari-
ate analyses of variance (ANOVAs) and chi-square tests
were used to compare the cannabis groups with respect
to sociodemographic, military, and clinical characteristics.
Third, multivariable logistic regression analyses and analy-
ses of covariance (ANCOVAs) were conducted to compare
rates of current treatment utilization, psychiatric comor-
bidities, functioning, and strategies for coping with PTSD
symptoms between the cannabis groups; these analyses
were adjusted for sociodemographic, military, and clini-
cal characteristics that differed between the groups at the
bivariate level (p<.). To control for the impact of mul-
tiple comparisons on the familywise error rate (FWER),
Bonferroni corrections were applied such that p<. was
indicative of statistically significant associations. Effect
6HILL .
sizes were calculated using odds ratios (ORs) for categor-
ical variables and Cohen’s dfor continuous variables.
RESULTS
Of the , veterans in the full sample, .% (n=)
met the criteria for current subthreshold or threshold
PTSD. Seven of these veterans refused to answer ques-
tions about their cannabis use and were excluded from the
analyses. Of the remaining veterans, .% (n=)
denied any cannabis use in the past months, .% (n=
) reported using cannabis less than weekly, and .%
(n=) reported using cannabis more than weekly. Vet-
erans included in the analyses were – years old (M=
. years, SD =.) and predominantly male (.%);
.% were non-Hispanic White, .% were non-Hispanic
Black, .% were Hispanic, and .% were multiracial or
identified their race as “other.” Combat veterans com-
prised .% of the sample, and .% of veterans reported
having enlisted in the military. Table presents sociode-
mographic, military, and clinical characteristics of the full
sample and the three cannabis groups.
Table shows the results of the multivariable models
predicting treatment utilization, psychiatric comorbidities,
and functioning variables after controlling for sociode-
mographic, military, and clinical differences between the
cannabis groups. After applying Bonferroni corrections
to control the FWER, the results revealed no significant
differences between the groups in current mental health
treatment engagement, but veterans who reported using
cannabis more than weekly were significantly more likely
to screen positive for co-occurring psychiatric disorders
than veterans who reported no cannabis use (MDD: OR
=., GAD: OR =., SI: OR =.) or those who used
cannabis less than weekly (MDD: OR =., GAD: OR =
., SI: OR =.); there were no significant differences in
psychiatric comorbidities between the no cannabis use and
less than weekly cannabis use groups. In addition, veter-
ans who used cannabis more than weekly scored lower
on a measure of cognitive functioning than veterans who
reported no cannabis use, d=., who scored lower than
veterans who reported using cannabis less than weekly,
d=.. The groups did not significantly differ with
respect to mental functioning, physical functioning, or psy-
chosocial difficulties.
Table shows results of the multivariable models pre-
dicting the use of PTSD coping strategies, again after
adjustment for covariates and Bonferroni corrections. Rel-
ative to participants in both the no cannabis use, OR =
., and less than weekly cannabis use groups, OR =.,
veterans who used cannabis more than weekly were more
likely to use an avoidant coping style to manage their PTSD
symptoms. Specifically, veterans who used cannabis more
than weekly were more likely than those who did not
report cannabis to endorse using substances, OR =., as
one of their top three strategies for managing their PTSD
symptoms; they were also more likely than participants
who either did not use cannabis, OR =., or used cannabis
less than weekly, OR =., to endorse using behavioral
disengagement to manage their PTSD symptoms. Veterans
who reported using cannabis less than weekly were more
likely than those who reported no cannabis use to endorse
substance use as a coping strategy, OR =., but less likely
to use behavioral disengagement, OR =.. These two
groups did not significantly differ in their overall use of
avoidant coping strategies to manage PTSD symptoms.
DISCUSSION
To our knowledge, the current study was the first to exam-
ine psychiatric and functional correlates of cannabis use
in a nationally representative sample of U.S. military vet-
erans with subthreshold or full PTSD. Compared with vet-
erans who did not use cannabis or used it infrequently,
those who used cannabis frequently were roughly twice
as likely to screen positive for co-occurring MDD, GAD,
and SI; showed small-to-moderate decrements in cogni-
tive functioning; and were – times more likely to endorse
using avoidance strategies as a primary means of man-
aging their PTSD symptoms. Notably, these associations
persisted even after conservative Bonferroni corrections
and stringent adjustment for sociodemographic, military,
and clinical characteristics, including other substance use
and current PTSD symptom severity.
The present results mirror findings that cannabis use
is linked to a broad range of psychiatric problems in the
general population of U.S. military veterans and civilian
adults (Hasin, ; Hill, Nichter, Norman, et al., )
as well as in treatment-seeking samples of veterans with
PTSD (Bryan et al., ). However, they differ from the
results of a large cross-sectional study of Canadian adults,
which indicated that PTSD was less strongly associated
with depressive symptoms and SI among individuals who
reported versus denied past-year cannabis use (Lake et al.,
). In the current study, veterans who used cannabis
frequently were substantially more likely than those who
did not use cannabis to screen positive for all psychiatric
comorbidities, and those who used infrequently reported
similar levels of psychiatric comorbidities as those who
denied cannabis use. This discrepancy could be due to
differences between populations and regulatory environ-
ments; for example, it is possible that Canadian civilians
and U.S. military veterans differ demographically or that
U.S. veterans who seek out cannabis in the United States,
CANNABIS USE IN VETERANS WITH PTSD SYMPTOMS 7
TABLE 1 Sociodemographic, military, and health characteristics of veterans with current subthreshold/threshold posttraumatic stress disorder (PTSD), by past--month cannabis use
Tot al (N=608)
No cannabis use (n=497,
weighted 80.1%)
Less than weekly cannabis
use (n=59, weighted 9.6%)
Greater than weekly cannabis
use (n=52, weighted 10.3%)
Weighted MSD Weighted MSD Weighted MSD Weighted MSD F(2, 660)
Age (years) . . . .a. .a,b . .b.*
ACEs . . . .a. .a. .b.*
Number of lifetime
traumatic events
. . . .a. .a. .a.
Past-month PTSD
severity (PCL-)
. . . .a. .a,b . .b.*
Number of medical
conditions
. . . .a. .a. .a.
n%n%n%n%χ(,N=)
Male sex . .a .a .a.
White race and
ethnicity
. .a .a .a.
Some college . .a .a,b .b.*
Annual household
income >
$, (USD)
. .a .b .b.*
Married or
partnered
. .a .a .b.*
Retired . .a .a .a.
VA primary health
care
. .a .a .a.
Enlisted into
military
. .a .b .a,b .
Combat veteran . .a .a,b .b.*
Military sexual
trauma
. .a .a .a.
Lifetime AUD . .a .a .a.*
Lifetime nicotine
dependence
. .a .a,b .b.*
Past-year alcohol
consumption
. . . .a. .b. .b.*
Note: Weighted prevalence estimates are within the subsample of veterans with subthreshold/threshold PTSD. Groups with different subscripts differed at p<.. PTSD =posttraumatic stress disorder; PCL- =PTSD
Checklist for DSM-5;VA=Veterans Affairs; ACEs =adverse childhood experiences; AUD =alcohol use disorder.
*p<..
8HILL .
TABLE 2 Psychiatric treatment, comorbidities, and functioning in veterans with current subthreshold/threshold posttraumatic stress disorder (PTSD), by past--month cannabis use
Multivariate analysesa
None
(n=497,
80.1%)
<Weekly
(n=59, 9.6%)
>Weekly
(n=52, 10.3%)
>Weekly use vs.
no use
>Weekly use vs.
<weekly use
<Weekly use vs.
no use
Variable n%n%n%χ2(2) NWa ld aOR 95% CI aOR 95% CI aOR 95% CI
Treatment . . . . . . [., .] . [., .] . [., .]
Psychiatric comorbidities
MDD . . . .*** .*** . [., .] . [., .] . [., .]
GAD . . . .*** .*** . [., .] . [., .] . [., .]
SI . . . .*** .*** . [., .] . [., .] . [., .]
Functioning measures
MSEMSEMSEF(2, 605) pddd
Cognitive function . . . . . . . <. −. −. .
Physical function . . . . . . . . . . −.
Mental function . . . . . . . . −. −. .
Psychosocial
difficulties
. . . . . . . . . . −.
Note: All prevalence estimates are weighted and within the subsample of veterans with subthreshold/threshold PTSD. aOR =adjusted odds ratio; MDD =major depressive disorder; GAD =generalized anxiety disorder;
SI =suicidal ideation.
aOdds ratios and means for multivariable analyses were adjusted for age, educational attainment, income, marital status, combat veteran status, adverse childhood experiences, lifetime alcohol use disorder, lifetime
nicotine dependence, past-year alcohol consumption, and past-month PTSD symptoms.
***p<. (Bonferroni correction applied).
CANNABIS USE IN VETERANS WITH PTSD SYMPTOMS 9
TABLE 3 Strategies for coping with posttraumatic stress disorder (PTSD) symptoms in veterans with current subthreshold/threshold PTSD, by past--month cannabis use
Multivariate analysesa
None
(n=497, 80.1%)
<Weekly
(n=59, 9.6%)
>Weekly
(n=52, 10.3%)
>Weekly use vs.
no use
>Weekly use vs.
<weekly use
<Weekly use vs.
no use
Variable n%n%n%χ2(2, N=608) Wald aOR 95% CI aOR 95% CI aOR 95% CI
Any self-sufficient . . . . – – – – – – –
Humor . . . . . . [., .] . [., .] . [., .]
Active coping . . . . – – – – – – –
Acceptance . . . . . . [., .] . [., .] . [., .]
Religion . . . . . . [., .] . [., .] . [., .]
Positive reframingb . . . – – – – – – – –
Planningb . . . – – – – – – – –
Any social support . . . . . . [., .] . [., .] . [., .]
Venting . . . . – – – – – – –
Emotional support . . . . – – – – – – –
Instrumental
supportb
. . . – – – – – – – –
Any avoidant . . . .*** .*** . [., .] . [., .] . [., .]
Substance use . . . .*** .*** . [., .] . [., .] . [., .]
Self-distraction . . . . – – – – – – –
Disengagement . . . .*** .*** . [., .] . [., .] . [., .]
Self-blame . . . . – – – – – – –
Denialb . . . – – – – – – – –
Note: All prevalence estimates are weighted and within the subsample of veterans with subthreshold/threshold PTSD. aOR =adjusted odds ratio.
aOdds ratios and means for multivariable analyses were adjusted for age, educational attainment, income, marital status, combat veteran status, adverse childhood experiences, lifetime alcohol use disorder, lifetime
nicotine dependence, past-year alcohol consumption, and past-month PTSD symptoms. bComparisons for these strategies contained cells with fewer than five veterans; due to small cell sizes, inferential statistics were
not computed.
***p<. (Bonferroni correction applied).
10 HILL .
where federal prohibitions against cannabis use are in
place, are more predisposed to psychiatric problems.
It is also possible that Canadian civilians and U.S.
veterans may use cannabis products with different
cannabinoid concentrations, in different quantities and
frequencies, and/or with different motives. In support
of this notion, Lake and colleagues () found that
% of individuals who used cannabis in their sample
reported “low-risk” cannabis use, defined as not meeting
the criteria for CUD, and that the attenuated associations
between PTSD and depression and SI were only apparent
in this low-risk group. In contrast, more than one third
of veterans in the current sample screened positive for
CUD. This may be because U.S. veterans with PTSD who
have access to a range of medical cannabis preparations
have been found to prefer high-frequency use of high-risk
cannabis formulations (i.e., high THC/low cannabidiol
[CBD] smoked cannabis; Loflin et al., ). Although it
is important to note that even nondisordered cannabis
use has been linked to psychiatric problems in the veteran
population (Hill, Nichter, Norman, et al., ), these
results suggest that high-risk cannabis use may underlie
the elevated levels of depression, anxiety, and SI observed
among frequent cannabis users in the present study.
In addition to having more co-occurring psychiatric dis-
orders, veterans who reported using cannabis more than
weekly showed small-magnitude decrements in cognitive
functioning compared with those who denied cannabis use
and moderate decrements compared with veterans who
used cannabis less than weekly. Although previous epi-
demiologic studies examining cannabis and functioning in
the context of PTSD are scarce, small-to-moderate deficits
in cognitive functioning among individuals with frequent
cannabis use have been observed in the general population
(e.g., Lovell et al., ). On measures of emotional and
physical functioning, small-to-moderate absolute differ-
ences emerged between the cannabis use groups, but these
associations were not statistically significant after correct-
ing for multiple comparisons. Thus, additional studies
with larger samples are needed to clarify the magnitude
of these differences. Finally, the null association between
cannabis use and psychosocial difficulties converges with
evidence from two recent PTSD treatment studies. The first
study, which is currently the only known RCT to evalu-
ate whole-plant cannabis as a treatment for PTSD, found
no effect of cannabis compared with placebo on PTSD
symptoms or secondary outcomes including psychosocial
difficulties, anxiety, or depressive symptoms (Bonn-Miller
et al., ). The second study, which observed individu-
als using cannabis and a non–cannabis-using comparison
group over the course of a year, found no prospective dif-
ferences between the groups in terms of psychosocial dif-
ficulties, anxiety, or depression, despite finding a larger
reduction in PTSD symptoms in the cannabis group (Bonn-
Miller et al., ). The present results extend these find-
ings to suggest that cannabis use may not be positively or
negatively associated with psychosocial difficulties in the
broader population of veterans with PTSD symptoms.
A concerning finding to emerge from the current study
was that veterans who used cannabis more frequently
were no more likely than other veterans to be engaged
in current mental health treatment, despite having more
severe current PTSD symptoms; a higher likelihood of
co-occurring depression, anxiety, and SI; and poorer cog-
nitive functioning. This finding converges with evidence
of high dropout associated with cannabis use in clinical
trials of treatments for PTSD to suggest that individuals
who use cannabis regularly may have difficulty engaging
and maintaining in PTSD treatment, including trauma-
focused therapy (Bedard-Gilligan et al., ). It is pos-
sible that the higher reliance on avoidant coping strate-
gies to manage PTSD symptoms observed in the frequent
cannabis use group might prevent these veterans from
engaging in trauma-focused therapy. Because such thera-
pies require the approach rather than avoidance of trauma-
related stimuli (i.e., exposure therapy), veterans who
primarily rely on strategies such as substance use and
behavioral disengagement to manage PTSD symptoms
may be less likely to seek out or stay in treatment.
The strengths of the present study include the analysis
of data from a contemporary, nationally representative
sample of veterans spanning all war eras and all U.S.
military branches that included individuals who utilized
both VHA and non-VHA health care. Veterans answered
questions about a variety of unrelated topics in addition to
cannabis use and psychiatric measures, limiting the risk
of biased responding. Nevertheless, the results should be
interpreted in the context of several limitations. First, the
cross-sectional nature of the study precludes inferences
about the directions of the reported associations; thus,
it is unclear whether frequent cannabis use causes psy-
chiatric and functioning difficulties or if such difficulties
lead veterans to use cannabis more frequently. It is also
possible that certain risk factors may predispose some
individuals to both frequent cannabis use and more severe
clinical presentations; although we statistically adjusted
for potential confounds identified in Table , veterans
were not randomly assigned to cannabis use groups in
the current study, and other preexisting factors may have
influenced group differences on the outcome variables.
Second, most of the sample was male and/or White, with
an average age of years, potentially limiting generaliz-
ability to younger, female, and racial and ethnic minority
veterans.
Third, the study relied on self-report screening instru-
ments, which may be less accurate than structured
CANNABIS USE IN VETERANS WITH PTSD SYMPTOMS 11
clinical interviews, and we did not assess the types of
cannabis products consumed, routes of administration, or
recency of participants’ latest cannabis use. As correlates of
cannabis use might vary by cannabinoid content (Curran
et al., ) and route of administration (Jones et al., ),
studies using more fine-grained assessment and testing of
cannabis products and metabolites may enable researchers
to identify important moderators of the observed associ-
ations. In addition, the assessment of cannabis use fre-
quency in the current study captured average cannabis
use over months, and it is possible that some veterans
who used cannabis may have been abstinent from cannabis
more recently. Future studies should include more detailed
measures of the frequency and recency of cannabis use to
disentangle the potential effects of acute and chronic use.
Finally, the numbers of veterans in each active cannabis
use group were relatively small, which may have limited
statistical precision, and the inclusion of veterans with sub-
threshold PTSD may have captured some veterans who
were experiencing low levels of symptoms. Therefore, fur-
ther studies using larger samples with higher degrees of
clinical severity are warranted.
These limitations notwithstanding, the present results
provide the first known evidence suggesting that U.S.
veterans with subthreshold or threshold PTSD who use
cannabis frequently may be more likely than nonusers and
infrequent users to have a broad range of psychiatric and
functional difficulties, yet they are no more likely to engage
in mental health treatment. Thus, frequent cannabis use
may signal increased clinical severity and the need for tar-
geted interventions to help veterans benefit from mental
health care. The finding that veterans who used cannabis
frequently were twice as likely to report current SI is par-
ticularly concerning, as disordered cannabis use is strongly
linked to high-severity suicidal behavior (i.e., suicide plan-
ning) in the general veteran population (Hill, Nichter,
Loflin, et al., ), and as many as in veterans with
current SI are not engaged in mental health treatment
(Nichter et al., ). Although alternative explanations
cannot be ruled out, it is possible that using cannabis fre-
quently and/or to avoid PTSD symptoms contributed to
the difficulties observed in veterans in the current sample.
Research on the validity of guidelines for low-risk versus
hazardous cannabis use, such as the Lower-Risk Cannabis
Use Guidelines (Fischer et al., ), may be warranted
for this population and could help clinicians engage in
nuanced conversations with patients about their cannabis
use. Further research is also needed to test prospective
associations between cannabis use and co-occurring prob-
lems among veterans with PTSD symptoms and to develop
interventions to promote engagement and retention in
mental health treatment for these veterans.
OPEN PRACTICES STATEMENT
The study reported in this article was not formally prereg-
istered. Neither the data nor the materials have been made
available on a permanent third-party archive; requests for
the data or materials should be sent via email to the senior
author at robert.pietrzak@yale.edu.
AUTHOR NOTE
Author Melanie L. Hill is a consultant to Spectrum Ther-
apeutics, a Canopy Growth company. Mallory Loflin is
an employee of GW Pharmaceuticals/Greenwich Bio-
sciences and receives stock options as compensation. In
the past years, she also received compensation from FSD
Pharma for scientific advisory board membership. Robert
H. Pietrzak is a scientific consultant to Cogstate, Ltd., for
work unrelated to the current project. None of the other
authors have any conflicts of interest to declare.
ORCID
Melanie L. Hill https://orcid.org/---
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How to cite this article: Hill, M. L., Loflin, M.,
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Pietrzak, R. H. (). Cannabis use among U.S.
military veterans with subthreshold or threshold
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JournalofTraumaticStress,–.
https://doi.org/./jts.
