Depression Among Non-Daily Smokers Compared to Daily Smokers and Never-Smokers in the United States: An Emerging Problem

Gender differences in the relationship between nicotine exposure and symptoms of depression

BACKGROUND

Tobacco-derived nicotine exposure is linked to depression. However, the associations of nicotine and its metabolites with symptoms of depression, particularly concerning gender differences, remain underexplored.

METHODS

The characteristics and total nicotine equivalents (TNE) of 1001 subjects were determined. The association between the TNE and symptoms of depression, accounting for gender differences, was investigated using generalized linear models and subgroup analyses.

RESULTS

Men exhibited significantly greater levels of the nicotine exposure indicators TNE2, TNE3, TNE6, and TNE7 (P < 0.005). A significantly greater percentage of women (23.45 %) than men (9.81 %) exhibited symptoms of depression (P < 0.0001). In women, the relationship between the TNE and depression was reflected by a U-shaped curve with significant inflection points, particularly for TNE3, TNE6, and TNE7. Furthermore, in women, concentrations above 48.98 nmol/mL for TNE3, 53.70 nmol/mL for TNE6, and 57.54 nmol/mL for TNE7 were associated with 154 %, 145 %, and 138 % increases in the risk of depression, respectively. In contrast, these associations did not reach significance among men.

LIMITATIONS

The cross-sectional design limits the ability to infer causality between nicotine exposure and depressive symptoms. Larger-scale studies are needed to confirm these findings.

CONCLUSIONS

Gender could be a significant factor influencing the relationship between nicotine exposure levels and symptoms of depression. The impact of nicotine exposure on symptoms of depression should be particularly considered among women.

IMPLICATIONS

This study revealed the complex relationship between tobacco-related nicotine exposure and depressive symptoms, with a particular focus on gender differences. Our results revealed a distinct U-shaped correlation between total nicotine equivalents and depression in women, which differed from that in men. These findings emphasize the importance of tailoring clinical approaches to address nicotine exposure and manage depressive symptoms based on gender.

The InterSECT Framework: a proposed model for explaining population-level trends in substance use and emotional concerns

Across high-income countries, adolescent emotional concerns have been increasing in prevalence over the past two decades and it is unclear why this is occurring, including whether and how substance use relates to these changing trends. On the other hand, substance use has been generally declining, and little is known about the role of emotional concerns in these trends. Several studies have explored the changes in co-occurring substance use and emotional concerns among adolescents over time, with mixed results and inconsistent messaging about the implications of the findings. In response, we developed a theoretical framework for exploring the intersection between trends in substance use and emotional concerns (InterSECT Framework). This framework includes a discussion and related examples for 3 core hypotheses: (1) strengthening of co-occurrence, or the "hardening" hypothesis; (2) co-occurrence staying the same, or the "consistency" hypothesis; and (3) weakening of co-occurrence, or the "decoupling" hypothesis. This framework seeks to guide the conceptualization, evaluation, and understanding of changes in the co-occurrence of substance use and emotional concerns over time, including outlining a research agenda informed by pre-existing research and youth perspectives.

Examining temporal trends in psychological distress and the co-occurrence of common substance use in a population-based sample of grade 7-12 students from 2013 to 2019

PURPOSE

Characterizing trends and correlates of adolescent psychological distress is important due to observed global increases over the last 20 years. Substance use is a commonly discussed correlate, though we lack an understanding about how co-occurrence of these concerns has been changing over time.

METHODS

Data came from repeated, representative, cross-sectional surveys of grade 7-12 students across Ontario, Canada conducted biennially from 2013 to 2019. Poisson regression with robust standard errors was used to examine changes in the joint association between psychological distress (operationalized as Kessler-6 [K6] scores ≥ 13) and substance use over time. Weighted prevalence ratios (PR) and their 99% confidence intervals were estimated, where p < 0.01 denotes statistical significance.

RESULTS

The prevalence of psychological distress doubled between 2013 and 2019, with adjusted increases of about 1.2 times each survey year. This biennial increase did not differ based on sex, perceived social standing, school level, or any substance use. Students using substances consistently reported a higher prevalence of psychological distress (between 1.2 times and 2.7 times higher). There were similarly no differential temporal trends based on substance use for very high distress (K6 ≥ 19) or K6 items explored individually.

CONCLUSION

Psychological distress steeply increased among adolescents and substance use remains important to assess and address alongside distress. However, the magnitude of temporal increases appears to be similar for adolescents reporting and not reporting substance use.

Evaluating Alcohol Use Severity in Terms of Cigarette Smoking-Related Processes and Anxiety/Depression Among Adult Latinx Smokers

OBJECTIVE

Although empirical work focused on smoking-drinking comorbidity among Latinx persons is growing, no work has explored the relation between alcohol use severity in terms of co-occurring smoking processes and mental health. Therefore, the present investigation aimed to explore the prevalence and role of alcohol use severity in relation to clinically significant tobacco and mental health problems among English-speaking Latinx adults who smoke cigarettes.

METHODS

Participants included 338 English-speaking Latinx adults who smoked cigarettes daily (Mage = 35.5 years; SD = 8.65; age range 18-61; 37.3% female).

RESULTS

Results indicated that approximately 68% of male and 61% of female smokers scored above established clinical cutoffs for hazardous and harmful alcohol use and possible alcohol dependence. Moreover, alcohol use severity was associated with increased risk for cigarette dependence, perceived barriers for quitting, and more problematic symptoms when trying to quit. Alcohol use severity was also related to more severe anxiety and depressive symptoms.

CONCLUSIONS

Overall, the current findings suggest that intervening to reduce alcohol use severity may be important to improving smoking cessation and mental health among Latinx persons who smoke.

Unhealthy behaviors associated with mental health disorders: a systematic comparative review of diet quality, sedentary behavior, and cannabis and tobacco use

Background

There are well-established literatures documenting the associations between mental disorders and unhealthy behaviors such as poor diet quality, sedentary behavior, and cannabis and tobacco use. Few studies have attempted to understand the respective findings in light of each other, however.

Objective

The purpose of this review was to assemble comparable data for each behavior-disorder association and assess the associations in terms of their overall strength. The review aimed to include a representative, but not exhaustive, range of studies that would allow for explorative comparisons.

Methods

Eligible studies were identified via Pubmed searches and citation searching, restricted to publications no older than 2015 written in English. To obtain comparable data, only studies that reported findings as odds ratios were included, and risk of bias related to study samples, behavioral measurement disparities, and control variables was assessed via sensitivity analyses. Findings for each disorder were compared on the basis of different measures of central tendency.

Results

From 3,682 records, 294 studies were included. The review found evidence of associations between each of the four unhealthy behaviors and psychosis, depression, anxiety, bipolar disorder, attention-deficit/hyperactivity disorder (ADHD), and post-traumatic stress disorder (PTSD), while personality disorder was only investigated in relation to cannabis and tobacco use. In overall comparison, the associations were generally of similar strength, and only the association between cannabis use and personality disorder was exceptional in terms of being significantly stronger than its counterparts across disorders and across behaviors. Analyses of bias risk identified some influence from behavioral measurement disparities and lack of adequate statistical control, but findings were generally robust across a range of sensitivity analyses.

Conclusion

This explorative and comparative review found that poor diet quality, sedentary behavior, and cannabis and tobacco use are about equally strongly associated with a range of different mental disorders. Given the general nature of these associations, we should probably understand them to reflect a general and shared etiology. However, the findings in this review should be regarded as tentative until confirmed by more comprehensive investigations.

Differences in smoking behavior and beliefs about abstinence among Latinx individuals with and without depression who smoke cigarettes

There is a well-established relation between depression and smoking in the general population. However, past work focused on Latinx persons who smoke in relation to depressed affect has yielded inconsistent findings. The present investigation aimed to build on past research and evaluate differences among English-speaking Latinx adults who smoke combustible cigarettes with and without probable depression in terms of cigarette dependence, perceived barriers for quitting, severity of problems when quitting, and smoking abstinence expectancies. The current sample included 338 adult Latinx daily cigarette smokers (Mage = 35.53 years; SD = 8.65; age range 18-61; 37.3% female) that were recruited nationally throughout the US. Results indicated that among Latinx persons who smoke, those with probable depression (compared to those without) demonstrated higher levels of cigarette dependence, more severe problems when trying to quit, greater perceived barriers for quitting, and increased negative abstinence expectancies after adjusting for sociodemographic and concurrent substance use variables. Future work could build from this research to elucidate the role of depression in the maintenance and relapse of smoking among the Latinx population.

The Role of Perceived Neighborhood Cohesion in the Association between Depressive Symptoms and Cigarette Smoking

BACKGROUND

Greater depression has been linked to increased smoking rates. However, the mechanisms underlying this association are not fully understood. It is possible that high perceived neighborhood cohesion may serve as one such mechanism given its associations with decreased depression and smoking. Having increased levels of depression likely impacts one's perceptions of neighborhood cohesion, which could lead to further increases in depression and a need to manage these symptoms via cigarette smoking. As a first test of this theory, the current study examined the effect of neighborhood cohesion on the association between depressive symptoms and smoking frequency and quantity among past 30-day cigarette smokers.

METHODS

Participants were 201 combustible cigarette smokers (Mage = 48.33, SD = 11.64; 63.2% female; 68.2% White) who completed self-report measures as part of a larger study of environmental influences on cardiac health.

RESULTS

Greater depressive symptoms were associated with lower levels of perceived neighborhood cohesion, and there was a significant indirect effect of greater depressive symptoms on heavier smoking through decreased neighborhood cohesion (b = .07, SE = .04, 95% CI [.003, .15]). There was no significant indirect effect for daily smoking.

CONCLUSION

These results suggest that neighborhood cohesion is an important contextual factor that serves as one explanatory mechanism for the well-established relationship between depression and smoking quantity. Thus, there may be utility in implementing interventions focused on increasing neighborhood cohesion as a way to decrease smoking behavior.

Pathophysiology of nAChRs: limbic circuits and related disorders

Human epidemiological studies have identified links between nicotine intake and stress disorders, including anxiety, depression and PTSD. Here we review the clinical evidence for activation and desensitization of nicotinic acetylcholine receptors (nAChRs) relevant to affective disorders. We go on to describe clinical and preclinical pharmacological studies suggesting that nAChR function may be involved in the etiology of anxiety and depressive disorders, may be relevant targets for medication development, and may contribute to the antidepressant efficacy of non-nicotinic therapeutics. We then review what is known about nAChR function in a subset of limbic system areas (amygdala, hippocampus and prefrontal cortex), and how this contributes to stress-relevant behaviors in preclinical models that may be relevant to human affective disorders. Taken together, the preclinical and clinical literature point to a clear role for ACh signaling through nAChRs in regulation of behavioral responses to stress. Disruption of nAChR homeostasis is likely to contribute to the psychopathology observed in anxiety and depressive disorders. Targeting specific nAChRs may therefore be a strategy for medication development to treat these disorders or to augment the efficacy of current therapeutics.

Intersectionality of serious psychological distress, cigarette smoking, and substance use disorders in the United States: 2008-2018

BACKGROUND

Serious psychological distress (SPD) is common among adults who smoke cigarettes and among adults with substance use disorders (SUD). It is unknown whether the burden of SPD is even greater among individuals with both cigarette smoking and SUDs. This study examined the intersectionality of SPD, cigarette smoking, and SUD over time.

METHODS

Data came from annual, cross-sectional, nationally representative samples of the United States (US) National Survey on Drug Use and Health (individuals age 12+). Past-month SPD prevalences were estimated each year from 2008 to 2018 for adults age 18+ with current daily, current non-daily, former, and never cigarette smoking by SUD status (combined n = 441,286). Logistic regression models examined linear time trends of SPD.

RESULTS

In 2018, SPD was significantly more prevalent among adults in each smoking group with SUD versus those without SUD (daily 29.1% vs. 9.0%, non-daily 23.2% vs. 8.6%, former 19.5% vs. 3.2%, never 16.4% vs. 4.3%). After adjusting for sociodemographics, SPD prevalence increased over time across smoking statuses with a larger change for persons with SUD (AOR=1.07; 95% CI: 1.06, 1.09) vs. no SUD (AOR=1.03; 95% CI: 1.02. 1.04).

CONCLUSIONS

SPD was more than twice as common among adults with SUD who smoke cigarettes compared to those without SUD who do not smoke cigarettes, with the highest prevalence among adults with both SUD and daily smoking. While SPD has increased over time, differences depended on SUD status beyond the effect of cigarette smoking. These results provide further evidence for treating smoking and mental health problems together.

Cigarette Consumption Patterns of Non-Smokers, Occasional Smokers, and Daily Smokers in Selected ASEAN Countries

Background:

This study investigates the socio-demographic factors associated with smoking status in five Southeast Asian countries: Malaysia, Thailand, Indonesia, Vietnam, and Philippines.

Methods:

This cross-sectional study utilizes data of adults ≥15 years who completed the Global Adult Tobacco Surveys. Ordered probit analysis is used to account for the smoking statuses of non-smokers, occasional smokers, and daily smokers.

Results:

Malaysian and Vietnamese households with more family members face lower smoking likelihoods than otherwise. Urbanites in Philippines and rural residents in Thailand and Indonesia are more likely to smoke on occasional and daily basis than others. Males are consistently more likely to smoke occasionally or daily and less likely to be non-smokers than females across all countries. Younger middle-age (retiree) individuals aged 30-35 (≥60) years in Malaysia and Thailand exhibit higher (lower) likelihoods to smoke occasionally or daily than their younger cohorts aged 15-29 years. Individuals aged 30 years and above in Indonesia, Vietnam, and Philippines display higher daily smoking propensities than others. Higher education levels dampens smoking likelihoods and increases non-smoking propensities in all countries. Non-government or self-employed workers in all countries are more likely to smoke occasionally or daily than unemployed persons. Being married is associated with higher non-smoking likelihoods in Thailand although this association is not evident in Malaysia.

Conclusion:

These findings suggest that a portfolio of targeted interventions is necessary to meet the needs of specific subpopulations within the various countries.

Depression and substance use disorders: Clinical comorbidity and shared neurobiology

Mood disorders, including major depressive disorder (MDD), are the most prevalent psychiatric illnesses, and pose an incredible burden to society, both in terms of disability and in terms of costs associated with medical care and lost work time. MDD has extremely high rates of comorbidity with substance use disorders (SUD) as many of the same neurobiological circuits and molecular mechanisms regulate the reward pathways disrupted in both conditions. MDD may induce SUDs, SUD may contribute to MDD development, or underlying vulnerabilities and common life experience may confer risk to developing both conditions. In this chapter we explore theories of MDD and SUD comorbidity, the neurobiological underpinnings of depression, overlapping cellular and molecular pathways for both conditions, and current treatment approaches for these comorbid conditions.

Trend in the Prevalence of Non-Daily Smoking and Their Relationship with Mental Health Using the Korea Health and Nutrition Examination Survey

Introduction: Non-Daily Smoking (NDS), which is increasingly prevalent worldwide, has not yet attracted as much attention as has daily smoking in Asia. The aims of this study were to identify trends in the prevalence of NDS and to compare characteristics by age, gender, and mental health indicators such as depression, suicidality, and alcohol consumption in South Korea. Methods: We included 33,806 adults (aged ≥ 19 years) who participated in the Korean National Health and Nutrition Examination Survey (KNHNES) from 2010 to 2015. The dataset includes self-reported medical history and questionnaires that explore depression, suicidality, and alcohol use, which are known to be highly related to smoking. We divided the respondents into four groups according to smoking status: Never Smoking (NS, N = 20,270); Past Smoking (PS = 6835); Daily Smoking (DS = 5927), who reported smoking every day; and Non-Daily Smoking (NDS = 774), who reported that they sometimes smoke. Results: Increased NDS prevalence is observed in most age groups in both male and female adults despite the prevalence of total smoking and daily smoking gradually decreasing. Depression and suicidality were significantly more prevalent in the NDS than the NS group (Depression Odds ratio, OR = 1.72, 95% Confidence interval, CI = 1.31–2.26; Suicidality OR = 3.14, 95% CI = 1.40–7.02). NDS is also associated with a higher frequency of binge drinking and alcohol use disorder than NS (OR = 4.17, 95% CI = 3.49–4.99). Conclusions: This study suggests that more concern is warranted for NDS given the increasing prevalence and characteristics of poor mental health in NDS respondents.

Increasing Depression and Substance Use Among Former Smokers in the United States, 2002-2016

INTRODUCTION

Mental health and substance use problems are associated with smoking relapse among former smokers. Yet, little is known about the prevalence of mental health and substance use among former smokers in the U.S. In addition, it is unknown whether the prevalence of these conditions has changed over time as former U.S. smokers have grown to outnumber current U.S. smokers. This study, which was conducted in 2018 and 2019, examined the prevalence and trends over time in depression (2005-2016), marijuana use (2002-2016), and alcohol use problems (2002-2016) among former U.S. smokers.

METHODS

The National Survey on Drug Use and Health is an annual, nationally representative, cross-sectional study. Data from U.S. individuals who were aged ≥18 years in 2002-2016 were included. Former smokers were defined as having smoked ≥100 lifetime cigarettes and no past-year cigarettes.

RESULTS

From 2005 to 2016, the prevalence of major depression increased from 4.88% to 6.04% (AOR=1.01, 95% CI=1.00, 1.03, p=0.04). From 2002 to 2016, past-year marijuana use rose from 5.35% to 10.09% (AOR=1.08, 95% CI=1.07, 1.09, p<0.001) among former smokers. Past-month binge alcohol use also increased from 17.22% to 22.33% (AOR=1.03, 95% CI=1.02, 1.04, p<0.001), although the prevalence of past-year alcohol abuse or dependence did not change.

CONCLUSIONS

Depression and substance use, which are factors associated with increased risk for cigarette use relapse, appear to be increasing over time among former U.S. smokers. Increased awareness of these trends may be important for clinical and public health efforts to direct attention to conditions potentially threatening sustained abstinence among former smokers.

Trends in Illicit Drug Use Among Smokers and Nonsmokers in the United States, 2002-2014

OBJECTIVE

Cigarette smoking has declined in the United States. Still, identifying prevalent and modifiable barriers to quitting can help inform the next steps for tobacco control. Illicit drug use, which may be increasingly common in the United States, could be one such factor. We investigated the relationship between past-month illicit drug use and cigarette smoking status and estimated trends in the prevalence of past-month illicit drug use by cigarette smoking status from 2002 to 2014 in the United States.

METHODS

The 2002-2014 National Survey on Drug Use and Health was used to obtain nationally representative data on past-month illicit drug use.

RESULTS

From 2002 to 2014, past-month illicit drug use (for all drugs considered) was nearly 5 times more common among current smokers than among never smokers (adjusted odds ratio = 4.79) and nearly twice as prevalent in former smokers as in never smokers (adjusted odds ratio = 1.99). Illicit drug use increased linearly over time from 2002 to 2014 in the entire general population (ie, across and within current smokers, former smokers, and never smokers). This increasing trend in drug use was most rapid among former smokers (relative to current smokers and never smokers) and was largely, but not entirely, driven by increases in cannabis use.

CONCLUSIONS

Illicit drug use is most prevalent among current cigarette smokers. Yet, the rate of increase in illicit drug use prevalence was most rapid among former smokers. Because former smokers outnumber current smokers in the general population, it may be important to monitor former smokers into the future for potential negative drug-related outcomes.

Depressive symptoms and suicidal behaviours in adolescent non-daily smokers compared to daily smokers and never-smokers in Korea: National cross-sectional study

INTRODUCTION

We aimed to investigate the association of non-daily smoking with depressive symptoms and suicidal behaviours among adolescents by analysing data from the 2016 Korean Youth Risk Behavior Web-based Survey (KYRBWS), a national school-based survey.

METHODS

We analysed data from a nationally representative sample of Korean adolescents aged 12-18 years (n = 65,528). We investigated the risks of depressive symptoms, suicide ideation, plan and attempt in adolescent non-daily smokers using multiple logistic regression analyses after adjusting for confounding factors. Taking into account the trajectory of smoking patterns in adolescents, we assessed all analyses with stratification by early (aged 12-15) and late (aged 16-18) adolescents.

RESULTS

Among early adolescents, non-daily smokers were more likely to have depressive symptoms, suicide ideation and plan compared with never smokers and even more likely to have depressive symptoms compared with daily smokers. Among late adolescents, non-daily smokers had higher risks of depressive symptoms, suicide ideation, plan and attempt than never smokers, whereas the risk for suicide attempts was lower than daily smokers.

CONCLUSIONS

Our findings suggest that non-daily smoking in adolescents was associated with risks for depressive symptoms and suicidal behaviours, and the association was more prominent in early adolescents. Careful attention on the mental health of adolescent non-daily smokers is needed because this is an increasing and easily overlooked group.

Factors associated with changing cigarette consumption patterns among low-intensity smokers: Longitudinal findings across four waves (2008-2012) of ITC Mexico Survey

Background

Light and intermittent smoking has become increasingly prevalent as smokers shift to lower consumption in response to tobacco control policies. We examined changes in cigarette consumption patterns over a four-year period and determined which factors were associated with smoking transitions.

Methods

We used data from a cohort of smokers from the 2008–2012 ITC Mexico Survey administrations to investigate transitions from non-daily (ND; n = 669), daily light (DL; ≤5 cigarettes per day (cpd); n = 643), and daily heavy (DH; >5 cpd; n = 761) smoking patterns. To identify which factors (i.e., sociodemographic measures, perceived addiction, quit behavior, social norms) were associated with smoking transitions, we stratified on smoking status at time t (ND, DL, DH) and used multinomial (ND, DL) and binomial (DH) logistic regression to examine transitions (quitting/reducing or increasing versus same level for ND and DL, quitting/reducing versus same level for DH).

Results

ND smokers were more likely to quit at follow-up than DL or DH smokers. DH smokers who reduced their consumption to ND were more likely to quit eventually compared to those who continued as DH. Smokers who perceived themselves as addicted had lower odds of quitting/reducing smoking consumption at follow-up compared to smokers who did not, regardless of smoking status at the prior survey. Quit attempts and quit intentions were also associated with quitting/reducing consumption.

Conclusions

Reducing consumption may eventually lead to cessation, even for heavier smokers. The findings that perceived addiction and quit behavior were important predictors of changing consumption for all groups may offer insights into potential interventions.

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Smoking transitions were evaluated in a cohort of Mexican smokers.

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The cohort consisted mostly of understudied light and intermittent smokers (LITS).

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Reductions in smoking intensity were found to facilitate smoking cessation.

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Greater perceived addiction inhibited cessation for smokers at all levels of intensity.

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LITS patterns warrant attention as number of low-intensity smokers worldwide grows.

Metabotropic Glutamatergic Receptor 5 and Stress Disorders: Knowledge Gained From Receptor Imaging Studies

The metabotropic glutamatergic receptor subtype 5 (mGluR5) may represent a promising therapeutic target for stress-related psychiatric disorders. Here, we describe mGluR5 findings in stress disorders, particularly major depressive disorder (MDD), highlighting insights from positron emission tomography studies. Positron emission tomography studies report either no differences or lower mGluR5 in MDD, potentially reflecting MDD heterogeneity. Unlike the rapidly acting glutamatergic agent ketamine, mGluR5-specific modulation has not yet shown antidepressant efficacy in MDD and bipolar disorder. Although we recently showed that ketamine may work, in part, through significant mGluR5 modulation, the specific role of mGluR5 downregulation in ketamine's antidepressant response is unclear. In contrast to MDD, there has been much less investigation of mGluR5 in bipolar disorder, yet initial studies indicate that mGluR5-specific treatments may aid in both depressed and manic mood states. The direction of modulation needed may be state dependent, however, limiting clinical feasibility. There has been relatively little study of posttraumatic stress disorder or obsessive-compulsive disorder to date, although there is evidence for the upregulation of mGluR5 in these disorders. However, while antagonism of mGluR5 may reduce fear conditioning, it may also reduce fear extinction. Therefore, studies are needed to determine the role mGluR5 modulation might play in the treatment of these conditions. Further challenges in modulating this prevalent neurotransmitter system include potential induction of significant side effects. As such, more research is needed to identify level and type (positive/negative allosteric modulation or full antagonism) of mGluR5 modulation required to translate existing knowledge into improved therapies.

Trends in Daily Cannabis Use Among Cigarette Smokers: United States, 2002-2014

OBJECTIVES

To estimate changes in the prevalence of daily cannabis use among current, former, and never cigarette smokers from 2002 to 2014 in the United States.

METHODS

The National Survey on Drug Use and Health is a nationally representative cross-sectional study conducted annually among persons aged 12 years and older in the United States.

RESULTS

Daily cannabis use occurs nearly exclusively among nondaily and daily cigarette smokers compared with former and never smokers (8.03%, 9.01%, 2.79%, 1.05%, respectively). Daily cannabis use increased over the past decade among both nondaily (8.03% [2014] vs 2.85% [2002]; linear trend P < .001) and daily smokers (9.01% [2014]; 4.92% [2002]; linear trend P < .001). Daily cannabis use increased most rapidly among former cigarette smokers (2.79% [2014] vs 0.98% [2002]; linear trend P < .001).

CONCLUSIONS

Daily cannabis use occurs predominantly among cigarette smokers in the United States. Daily cannabis use increased among current, former, and never smokers over the past decade, with particularly rapid increases among youth and female cigarette smokers. Future research is needed to monitor the observed increase in daily cannabis use, especially among youths and adults who smoke cigarettes.