Conscription Assessment Research Articles

Atopic dermatitis and cognitive function: asibling comparison study among males inSweden.

A previous study indicated that atopic dermatitis (AD) was associated with better cognitive function in males during late adolescence. This association was examined among 2 021 369 males who had a medical examination and cognitive function testing during a military conscription assessment in late adolescence in Sweden. Sibling-comparison analysis to tackle confounding indicated that AD is associated with poorer cognitive function, suggesting AD in childhood is detrimental for the development of cognitive function.

Myopia in late adolescence and subsequent multiple sclerosis among men.

Risk factors such as low vitamin D level has been implicated in the etiology of multiple sclerosis (MS) and may be relevant to myopia, such that there may be an association between myopia and MS. Using linked Swedish national register data, we conducted a cohort study of men who were born in Sweden between 1950 and 1992, lived in Sweden between 1990 and 2018, and enrolled in military conscription assessment (n=1,847,754). Myopia was defined based on the spherical equivalent refraction measured at conscription assessment, around age 18 years. Multiple sclerosis was identified using the Patient Register. Cox regression produced hazard ratios (HR) with 95% confidence intervals (95% CI), with adjustment for demographic and childhood socioeconomic characteristics and residential region. Due to changes in the assessment of refractive error, the analysis was stratified into two groups by the year of conscription assessment: 1969-1997 and 1997-2010. Among 1,559,859 individuals during a maximum of 48 years of follow-up from age 20 to 68 years (44,715,603 person-years), there were 3,134 MS events, and the incidence rate 7.0 (95% CI [6.8, 7.3] per 100,000 person-years). Among individuals with conscription assessments during 1997-2010, there were 380 MS events. There was no evidence of an association between myopia and MS, with HR 1.09 (95% CI 0.83, 1.43). Among individuals who underwent conscription assessment in 1969-1997, there were 2754 MS events. After adjusting for all covariates, there was no evidence of an association between myopia and MS (HR 0.99 [95% CI 0.91, 1.09]). Myopia in late adolescence is not associated with a subsequent raised risk of MS and thus there does not appear to be important shared risk factors.

Systemic inflammation measured by erythrocyte sedimentation rate and cognitive function among young men in Sweden: A within-sibling analysis.

This study assesses the extent to which the association between erythrocyte sedimentation rate, a marker of inflammation, and cognitive function is explained by shared familial factors using within-sibling analyses. Men who were born in Sweden between 1950 and 1965 and recorded in the Swedish Military Conscription Register between 1969 and 1983 were included (N = 632,396). Erythrocyte sedimentation rate and cognitive function were measured at the conscription assessment (median age = 18.3 years, with a range from 15.5 to 28.5 years). Conventional linear regression and multilevel linear regression with a hybrid modeling approach were used, with the latter to obtain within-effect estimation in which unmeasured familial confounding shared by siblings was controlled for. We found that the association between erythrocyte sedimentation rate and cognitive function at conscription assessment was partly accounted for by, but remained independent of, shared familial factors.

Visual Acuity and the Risk of Cycling Injuries: Register-Based Cohort Study From Adolescence to Middle-age.

Cycling is increasingly encouraged in many countries as an inexpensive and healthy choice of transportation. Operating any vehicle on the road requires high visual acuity, but few studies to our knowledge have examined the association between vision and cycling injuries. We examined whether poorer visual acuity is associated with increased risk of fatal and nonfatal cycling injuries. We used prospectively recorded register data for 691,402 men born between 1970 and 1992 in Sweden. We followed these men from an average age of 18 years, when visual acuity was assessed during the conscription assessment, to age 45 at the latest. We identified fatal and nonfatal cycling and car injuries using Patient and Cause of Death registers. Cox regression models were used to estimate hazard ratios and 95% confidence intervals. Based on visual acuity for the eye with the best vision, moderately impaired acuity 0.9 to 0.6 when wearing refractive correction was associated with increased risk for cycling injuries (hazard ratio = 1.44 [95% confidence interval = 1.16, 1.79]) compared with unimpaired vision (uncorrected visual acuity 1.0) and after adjustment for a wide range of potential confounders. This association remained consistent across various sensitivity analyses. Visual acuity was not associated with car injury risk. In this cohort study, poorer vision was specifically associated with a higher rate of cycling injuries.

Same-Sex Partnership and Cardiovascular Disease in Men: The Role of Risk Factors in Adolescence.

Purpose: We aimed to examine if same-sex partnership in men is associated with cardiovascular disease (CVD) and whether this relationship can be explained by accumulated risk factors in late adolescence using causal mediation analysis. Methods: All men born in Sweden between 1952 and 1956, who participated in mandatory Swedish military service conscription assessments, and had ever been recorded as being in an opposite-sex marriage or a legally recognized same-sex partnership were included (n = 156,612). Hospital-diagnosed CVD between ages 31 and 58 years was identified using medical records. Men were grouped into an opposite-sex marriage category or a same-sex partnership category based on marital status. Risk factors for CVD in late adolescence were identified using five biomarkers (systolic and diastolic blood pressure, pulse pressure, body mass index, and erythrocyte sedimentation rate) obtained at a conscription examination between ages 16 and 20 years. Birth year, childhood socioeconomic characteristics, physical and psychological characteristics in late adolescence, and mental health before the onset of CVD were treated as potential confounders. Results: Being in a same-sex partnership was associated with increased CVD risk compared with being in an opposite-sex marriage after controlling for potential confounders and risk factors; hazard ratio = 1.61, 95% confidence interval (CI) = 1.27-2.04. The risk factors in late adolescence explained 6.36% (95% CI = 2.72-12.74) of the increased CVD risk associated with being in same-sex partnerships compared with being in opposite-sex marriages. Conclusions: CVD risk factors accumulated by late adolescence may only partially account for the association between same-sex partnerships and cardiovascular health.

Risk of depression following traumatic limb amputation-a general population-based cohort study.

Background: Individuals with traumatic limb amputation (TLA) may be at risk of depression, but evidence of increased depression after TLA from longitudinal studies has been limited. It is also unknown whether physical function, cognitive function, and employment prior to amputation affects depression risk. We aimed to examine longitudinal associations between TLA and depression in working age men, and to explore the role of pre-amputation occupational and individual characteristics. Methods: A Swedish national register-based cohort of 189,220 men born between 1952 and 1956, and who attended conscription assessments in adolescence, was followed from 1985 to 2009. Physical, cognitive, and psychological characteristics were measured at the conscription examination, and occupational information was obtained from the 1985 census. Main outcome measures were hospital inpatient and outpatient admissions for depression. Results: In total, 401 men underwent TLA; mean age at amputation was 42.5 years (SD 7.4). Cox regression produced an unadjusted hazard ratio (95% confidence interval) of 2.61 (1.62-4.21) for risk of subsequent depression associated with TLA compared with the general population. Adjustment for occupational, physical, cognitive, and psychological characteristics did not change the association much, producing a hazard ratio of 2.53 (1.57-4.08). Conclusions: TLA is associated with an increased risk of depression in men over more than two decades of follow up. Occupational and individual characteristics prior to amputation did not greatly change depression risk following amputation. We speculate that a coordinated combination of social support and medical management may help reduce persistent depression risk in men who experience amputation.

Atopic dermatitis and educational attainment

Atopic dermatitis (AD, often known as eczema) is a common skin disorder affecting up to 20% of children. However, our knowledge is incomplete for some long‐term effects of this condition such as educational attainment, meaning the level of education a person reaches at school, university or college. AD is usually visible, causes itching and sometimes sleeplessness, which may therefore impact on a person's education. In this study the level of education among adolescent males with and without AD was compared, as was cognitive function (brain processes that allow us to carry out tasks) and stress resilience (ability to cope with stress), using Swedish register data. The study included 234,715 men who underwent military conscription assessments aged 17‐20 years between 1969 and 1976: these assessments involved extensive physical and psychological examinations including a written cognitive function test. In total 1,673 (0.7%) had an AD diagnosis. Surprisingly, AD was not associated with reduced levels of academic attainment or cognitive function. In fact, slightly higher levels of education and cognitive function were observed and appear to be explained by men with AD having parents with a more advantaged socioeconomic position, resulting in improved educational performance. However, those with AD tended to have a lower ability to cope with stress, which has been linked with adverse mental and physical health outcomes in later adulthood.

Overweight and obesity during adolescence increases the risk of renal cell carcinoma.

While overweight among adults has been linked with renal cell carcinoma (RCC) risk, little is known about the potential influence of overweight and obesity during adolescence. To ascertain if adolescent body mass index is associated with subsequent risk of RCC, we identified a cohort of 238,788 Swedish men who underwent mandatory military conscription assessment between 1969 and 1976 at a mean age of 18.5 years. At the time of conscription assessment, physical and psychological tests were performed including measurements of height and weight. Participants were followed through linkage to the Swedish Cancer Registry to identify incident diagnoses of RCC. The association between body mass index (BMI, kg/m2) at conscription assessment and subsequent RCC was evaluated using multivariable Cox regression. During a follow‐up of up to 37 years, 266 men were diagnosed with RCC. We observed a trend for higher RCC risk with increasing BMI during adolescence, where one‐unit increase in BMI conferred a 6% increased risk of RCC (95% CI 1.01–1.10). compared to normal weight men (BMI 18.5‐ < 25), men with overweight (BMI 25‐ < 30) or obesity (BMI ≥30) had hazard ratios for RCC of 1.76 (95% CI 1.16–2.67) and 2.87 (95% CI 1.26–6.25), respectively. The link between overweight/obesity and RCC appear to be already established during late adolescence. Prevention of unhealthy weight gain during childhood and adolescence may thus be a target in efforts to decrease the burden of RCC in the adult population.

Atopic dermatitis, educational attainment and psychological functioning: a national cohort study.

Atopic dermatitis (AD) might adversely affect academic performance, possibly through influences on psychological functioning such as stress resilience. To investigate the association of atopic dermatitis with stress resilience, cognitive function and educational attainment. We used data from a national cohort of men who underwent a military conscription examination at ages 17-20 years in Sweden between 1969 and 1976. All potential conscripts met a physician who assessed current or previous history of AD. Stress resilience was measured by a psychologist using a semistructured interview. The conscription assessment included a written cognitive function test. The highest level of education achieved was identified through record linkage. The study population included 234 715 men, 1673 (0·7%) of whom had a diagnosis of AD. AD was associated with a greater risk of low stress resilience [adjusted relative risk ratio (RRR) 1·60, 95% confidence interval (CI) 1·38-1·86]. AD was associated with higher cognitive function (β-coefficient 0·15, 95% CI 0·05-0·24) and higher educational level (RRR 1·29, 95% CI 1·13-1·47). However, adjustment for socioeconomic characteristics of the family of origin attenuated the magnitude of the associations and eliminated the statistical significance (β-coefficient 0·06, 95% CI -0·03 to 0·15; RRR 1·16, 95% CI 1·00-1·35). Swedish men with AD had lower stress resilience in late adolescence but did not have lower cognitive function or poorer educational attainment. The lower stress resilience associated with AD is consistent with an increased risk of possible long-term adverse health outcomes.

Sex of older siblings and psychological functioning

The aim was to investigate whether older siblings are associated with development of stress resilience in adolescence and if there are differences by sex of siblings. The study used a Swedish register-based cohort of men (n=664 603) born between 1970 and 1992 who undertook military conscription assessments in adolescence that included a measure of stress resilience: associations were assessed using multinomial logistic regression. Adjusted relative risk ratios (95% confidence intervals) for low stress resilience (n=136 746) compared with high (n=142 581) are 1.33 (1.30, 1.35), 1.65 (1.59, 1.71) and 2.36 (2.18, 2.54) for one, two and three or more male older siblings, compared with none. Equivalent values for female older siblings do not have overlapping confidence intervals with males and are 1.19 (1.17, 1.21), 1.46 (1.40, 1.51) and 1.87 (1.73, 2.03). When the individual male and female siblings are compared directly (one male sibling compared with one female sibling, etc.) and after adjustment, including for cognitive function, there is a statistically significant (p<0.005) greater risk for low stress resilience associated with male siblings. Older male siblings may have greater adverse implications for psychological development, perhaps due to greater demands on familial resources or inter-sibling interactions.

Cannabis Use and Incidence of Testicular Cancer: A 42-Year Follow-up of Swedish Men between 1970 and 2011.

Background: Given current drug policy reforms to decriminalize or legalize cannabis in numerous countries worldwide, the current study assesses the relation between cannabis use and the development of testicular cancer.Methods: The study included a population-based sample (n = 49,343) of young men ages 18-21 years who underwent conscription assessment for Swedish military service in 1969-1970. The conscription process included a nonanonymous questionnaire eliciting information about drug use. Conscription information was linked to Swedish health and administrative registry data. Testicular cancers diagnosed between 1970 and 2011 were identified by International Classification of Diseases-7/8/9/10 testicular cancer codes in the Swedish National Patient Register, the Cancer Register, or the Cause of Death Register. Cox regression modeling was used to estimate the hazards associated with cannabis use and time to diagnosis of testicular cancer.Results: No evidence was found of a significant relation between lifetime "ever" cannabis use and the subsequent development of testicular cancer [n = 45,250; 119 testicular cancer cases; adjusted HR (aHR), 1.42; 95% confidence interval (CI), 0.83-2.45]. "Heavy" cannabis use (defined as usage of more than 50 times in lifetime, as measured at conscription) was associated with the incidence of testicular cancer (n = 45,250; 119 testicular cancer cases; aHR 2.57; 95% CI, 1.02-6.50).Conclusions: The current study provides additional evidence to the limited prior literature suggesting cannabis use may contribute to the development of testicular cancer.Impact: Emerging changes to cannabis drug policy should consider the potential role of cannabis use in the development of testicular cancer. Cancer Epidemiol Biomarkers Prev; 26(11); 1644-52. ©2017 AACR.

Resilience to stress and risk of gastrointestinal infections.

Exposure to psychological stress can elicit a physiological response that may influence characteristics of the gastrointestinal mucosa, including increased intestinal permeability, in turn possibly increasing susceptibility to gastrointestinal infections. We investigated whether low stress resilience in adolescence is associated with an 'increased' risk of gastrointestinal infections in subsequent adulthood. Data were provided by Swedish registers for a cohort of 237 577 men who underwent military conscription assessment in late adolescence (1969-76). As part of the assessment procedure, certified psychologists evaluated stress resilience through semi-structured interviews. The cohort was followed from conscription assessment until 31 December 2009 (up to age 57 years). Cox regression assessed the association of stress resilience with gastrointestinal infections (n = 5532), with adjustment for family background measures in childhood and characteristics in adolescence. Peptic ulcer disease (PUD) in adulthood was modelled as a time-dependent covariate. Compared with high stress resilience, lower stress resilience was associated with a 'reduced' risk of gastrointestinal infections after adjustment for family background in childhood, characteristics in adolescence and PUD in adulthood, with hazard ratios (and 95% confidence intervals) of 0.88 (0.81-0.97) and 0.83 (0.77-0.88) for low and moderate stress resilience, respectively. Lower stress resilience in adolescence is associated with reduced risk of gastrointestinal infections in adulthood, rather than the hypothesized increased risk.

Severe infections and subsequent delayed cardiovascular disease.

Background Severe infections in adulthood are associated with subsequent short-term cardiovascular disease. Whether hospital admission for sepsis or pneumonia is associated with persistent increased risk (over a year after infection) is less well established. Design The design of this study was as a register-based cohort study. Methods Some 236,739 men born between 1952-1956 were followed from conscription assessments in adolescence to 2010. All-cause cardiovascular disease ( n = 46,754), including coronary heart disease ( n = 10,279) and stroke ( n = 3438), was identified through national registers 1970-2010 (at ages 18-58 years). Results Sepsis or pneumonia in adulthood (resulting in hospital admission) are associated with increased risk of cardiovascular disease in the years following infection. The risk is highest during the first year after the infection, with an adjusted hazard ratio (and 95% confidence intervals) of 6.33 (5.65-7.09) and a notably increased risk persisted with hazard ratios of 2.47 (2.04-3.00) for the second and 2.12 (1.71-2.62) for the third year after infection. The risk attenuated with time, but remained raised for at least five years after infection; 1.87 (1.47-2.38). The results are adjusted for characteristics in childhood, cardiovascular risk factors and medical history in adolescence. Similar statistically significant associations were found for coronary heart disease and stroke. Conclusions Raised risks of cardiovascular disease following hospital admission for sepsis or pneumonia were increased for more than five years after the infection, but with the highest magnitude during the first three years following infection, suggesting a period of vulnerability when health professionals and patients should be aware of the heightened risk for cardiovascular disease.

Precursors in adolescence of adult-onset bipolar disorder

BackgroundAlthough the estimated contribution of genetic factors is high in bipolar disorder, environmental factors may also play a role. This Swedish register-based cohort study of men examined if physical and psychological characteristics in late adolescence, including factors previously linked with bipolar disorder (body mass index, asthma and allergy), are associated with subsequent bipolar disorder in adulthood. Unipolar depression and anxiety are analysed as additional outcomes to identify bipolar disorder-specific associations. MethodsA total of 213,693 men born between 1952 and 1956, who participated in compulsory military conscription assessments in late adolescence were followed up to 2009, excluding men with any psychiatric diagnoses at baseline. Cox regression estimated risk of bipolar disorder, depression and anxiety in adulthood associated with body mass index, asthma, allergy, muscular strength stress resilience and cognitive function in adolescence. ResultsBMI, asthma and allergy were not associated with bipolar disorder. Higher grip strength, cognitive function and stress resilience were associated with a reduced risk of bipolar disorder and the other disease outcomes. LimitationsThe sample consisted only of men; even though the characteristics in adolescence pre-dated disease onset, they may have been the consequence of prodromal disease. ConclusionsAssociations with body mass index and asthma found by previous studies may be consequences of bipolar disorder or its treatment rather than risk factors. Inverse associations with all the outcome diagnoses for stress resilience, muscular strength and cognitive function may reflect general risks for these psychiatric disorders or intermediary factors.

Stress resilience and the risk of inflammatory bowel disease: a cohort study of men living in Sweden

ObjectiveTo determine if low psychosocial stress resilience in adolescence (increasing chronic stress arousal throughout life) is associated with an increased inflammatory bowel disease (IBD) risk in adulthood. Subclinical Crohn's disease...

Physical Fitness in Adolescence and Subsequent Inflammatory Bowel Disease Risk.

OBJECTIVES:Physical fitness may reduce systemic inflammation levels relevant to the risk of symptomatic Crohn's disease (CD) and ulcerative colitis (UC); we assessed if fitness in adolescence is associated with subsequent inflammatory bowel disease (IBD) risk, independent of markers of risk and prodromal disease activity.METHODS:Swedish registers provided information on a cohort of 240,984 men (after exclusions) who underwent military conscription assessments in late adolescence (1969–1976). Follow-up started at least 4 years after the conscription assessment until 31 December 2009 (up to age 57 years). Cox's regression assessed the association of physical fitness with CD (n=986) and UC (n=1,878) in separate models, with adjustment including: socioeconomic conditions in childhood; physical fitness, height, body mass index, and erythrocyte sedimentation rate (ESR) in adolescence; and subsequent diagnoses of IBD.RESULTS:Low fitness was associated with a raised risk of IBD, with unadjusted hazard ratios (and 95% confidence intervals) of 1.62 (1.31–2.00) for CD and 1.36 (1.17–1.59) for UC. The results were attenuated by adjustment, particularly for markers of prodromal disease activity to 1.32 (1.05–1.66) and 1.25 (1.06–1.48), respectively. Raised ESR in adolescence was associated with increased risks for subsequent CD (5.95 (4.47–7.92)) and UC (1.92 (1.46–2.52)).CONCLUSIONS:The inverse association of physical fitness with IBD risk is consistent with a protective role for exercise. However, evidence of disease activity before diagnosis was already present in adolescence, suggesting that some or all of the association between fitness and IBD may be due to prodromal disease activity reducing exercise capacity and therefore fitness.

Abstract PR12: Adolescent inflammation and body mass index in relation to colorectal cancer risk

Abstract Inflammation and obesity in adulthood have been associated with risk of colorectal cancer (CRC); however, less is known about the role of early-life inflammation and body mass index (BMI) in relation to CRC risk. We therefore sought to evaluate these associations in a cohort of 239,464 Swedish men compulsorily enlisted in the military in late adolescence (ages 16-20 years). At the time of the conscription assessment (1969-1976), erythrocyte sedimentation rate (ESR) was assayed as a measure of inflammation and height and weight were measured. The conscription registry has been linked with national cancer and mortality registries, and men have been followed for CRC through January 1, 2010. Over an average of 35 years of follow-up, 885 cases of CRC occurred, including 501 colon cancers and 384 rectal cancers. Cox regression was used to estimate Hazard Ratios (HRs) and corresponding 95% Confidence Intervals (95% CIs) adjusted for covariates, including childhood socioeconomic status. Men with high inflammation (ESR ≥ 15 mm/hr) in late adolescence had 63% higher risk of CRC (HR: 1.63; 95% CI: 1.08, 2.46) than men with low inflammation (ESR &amp;lt;10 mm/hr) (p-trend: 0.006). This association did not significantly differ by anatomic site (p-difference: 0.50), though the trend was statistically significant for cancers of the colon only (p-trend: 0.009). Late-adolescent BMI was also significantly associated with CRC risk (p-trend: &amp;lt;0.001), with obese adolescents (BMI ≥ 30 kg/m2) experiencing a 2.37-fold higher risk of CRC (HR: 2.37; 95% CI: 1.50, 3.74) than their normal weight counterparts (BMI 18.5-&amp;lt;25 kg/m2). Again, the association between BMI and cancer risk did not significantly vary by anatomic site (p-difference: 0.40), although the trend was statistically significant for cancers of the colon only (p-trend: &amp;lt; 0.001). These analyses were mutually adjusted for BMI and ESR, suggesting that both adolescent inflammation and BMI may be independently associated with CRC risk. Future research is needed to better understand how life-course inflammation and BMI relate to colorectal cancer. Citation Format: Elizabeth D. Kantor, Ruzan Udumyan, Lisa B. Signorello, Edward L. Giovannucci, Scott Montgomery, Katja Fall. Adolescent inflammation and body mass index in relation to colorectal cancer risk. [abstract]. In: Proceedings of the Thirteenth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2014 Sep 27-Oct 1; New Orleans, LA. Philadelphia (PA): AACR; Can Prev Res 2015;8(10 Suppl): Abstract nr PR12.

Remarriage after divorce and depression risk

As marriage is associated with lower depression rates compared with being single in men, we aimed to examine if remarriage compared with remaining divorced is also associated with a reduced depression risk. Swedish register data were used to define a cohort of men who were born between 1952 and 1956 and underwent a compulsory military conscription assessment in adolescence. This study population comprised men who were divorced in 1985 (n = 72,246). The risk of pharmaceutically treated depression from 2005 to 2009 was compared for those who remarried or remained divorced between 1986 and 2004. Cox proportional hazards analysis was used to estimate hazard ratios for the risk of depression identified by pharmaceutical treatment, with adjustment for a range of potential confounding factors including childhood and adulthood socioeconomic circumstances, cognitive, physical, psychological and medical characteristics at the conscription assessment. The results showed that, even though divorced men who remarried had markers of lower depression risk in earlier life such as higher cognitive and physical function, higher stress resilience and socioeconomic advantages than men who remained divorced, remarriage was associated with a statistically significant elevated risk of depression with an adjusted hazard ratio (and 95% confidence interval) of 1.27(1.03 1.55), compared with men who remained divorced. Remarriage following divorce is not associated with a reduced risk of depression identified by pharmaceutical treatment, compared with remaining divorced. Interpersonal or financial difficulties resulting from remarriage may outweigh the benefits of marriage in terms of depression risk.

Adolescent body mass index and erythrocyte sedimentation rate in relation to colorectal cancer risk

ObjectiveAdult obesity and inflammation have been associated with risk of colorectal cancer (CRC); however, less is known about how adolescent body mass index (BMI) and inflammation, as measured by erythrocyte...

Marijuana use and risk of lung cancer: a 40-year cohort study

Cannabis (marijuana) smoke and tobacco smoke contain many of the same potent carcinogens, but a critical-yet unresolved-medical and public-health issue is whether cannabis smoking might facilitate the development of lung cancer. The current study aimed to assess the risk of lung cancer among young marijuana users. A population-based cohort study examined men (n = 49,321) aged 18-20 years old assessed for cannabis use and other relevant variables during military conscription in Sweden in 1969-1970. Participants were tracked until 2009 for incident lung cancer outcomes in nationwide linked medical registries. Cox regression modeling assessed relationships between cannabis smoking, measured at conscription, and the hazard of subsequently receiving a lung cancer diagnosis. At the baseline conscription assessment, 10.5 % (n = 5,156) reported lifetime use of marijuana and 1.7 % (n = 831) indicated lifetime use of more than 50 times, designated as "heavy" use. Cox regression analyses (n = 44,284) found that such "heavy" cannabis smoking was significantly associated with more than a twofold risk (hazard ratio 2.12, 95 % CI 1.08-4.14) of developing lung cancer over the 40-year follow-up period, even after statistical adjustment for baseline tobacco use, alcohol use, respiratory conditions, and socioeconomic status. Our primary finding provides initial longitudinal evidence that cannabis use might elevate the risk of lung cancer. In light of the widespread use of marijuana, especially among adolescents and young adults, our study provides important data for informing the risk-benefit calculus of marijuana smoking in medical, public-health, and drug-policy settings.