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PubMed2002

Cannabis dependence in young adults: an Australian population study.

OBJECTIVES: The symptomatology of cannabis dependence remains ill-defined and its importance controversial. Compared with alcohol dependence, the symptom profile of cannabis dependence has received little attention. We aimed to (a) report cannabis use in a representative population of young adults, (b) examine cannabis dependence symptoms according to frequency in the dependence syndrome and (c) contrast the symptomatology of cannabis and alcohol syndromes. METHODS: 1601 young adults (mean age 20.7 years) from an Australian longitudinal cohort study (N=2032) were surveyed in 1998. Regular substance users were assessed for DSM-IV cannabis and alcohol dependence. Prevalence estimates allowed for sampling variation and attrition. RESULTS: Fifty-nine per cent reported life-time use of cannabis, 17% used at least weekly and 7% (11% males, 4% females) met criteria for cannabis dependence. Symptom prevalence in dependent cannabis users was: persistent desire 91%; unintentional use 84%; withdrawal 74%; excessive time obtaining/using 74%; continued use despite health problems 63%; tolerance 21%; and social consequences 18%. The combination of withdrawal, persistent desire and unintentional use was reported by 57%. Dependent cannabis users reported compulsive and out-of-control use more frequently than dependent alcohol users, withdrawal similarly and tolerance considerably less often. CONCLUSIONS: Cannabis use appears to be normative behaviour in young Australians. Progression beyond weekly use of cannabis carries a significant risk of dependence that should be considered in the public health response. The differing profiles of cannabis and alcohol dependence, particularly with regard to craving, draws attention to the need for further study of cannabis dependence as an important and distinct disorder in young adults.

Adolescent↗
PubMed1998

Cannabis use and psychosis.

This paper reviews evidence on two hypotheses about the relationship between cannabis use and psychosis. The first hypothesis is that heavy cannabis use may cause a "cannabis psychosis"-a psychosis that would not occur in the absence of cannabis use, the symptoms of which are preceded by heavy cannabis use and remit after abstinence. The second hypothesis is that cannabis use may precipitate schizophrenia, or exacerbate its symptoms. Evaluation of these hypotheses requires evidence of an association between cannabis use and psychosis, that is unlikely to be due to chance, in which cannabis use precedes psychosis, and in which we can exclude the hypothesis that the relationship is due to other factors, such as other drug use, or a personal vulnerability to psychosis. There is some clinical support for the first hypothesis. If these disorders exist they seem to be rare, because they require very high doses of THC, the prolonged use of highly potent forms of cannabis, or a pre-existing (but as yet unspecified) vulnerability. There is more support for the second hypothesis, in that a large prospective study has shown a linear relationship between the frequency with which cannabis has been used by age 18 and the risks over the subsequent 15 years of a diagnosis of schizophrenia. It is still unclear whether this means that cannabis use precipitates schizophrenia, whether it is a form of "self-medication", or whether the association is due to the use of other drugs, such as amphetamines, which heavy cannabis users are more likely to use. There is stronger evidence that cannabis use can exacerbate the symptoms of schizophrenia. Mental health services should identify patients with schizophrenia who use alcohol, cannabis and other drugs and advise them to abstain or to greatly reduce their drug use.

Journal Article↗
PubMed2004

Adverse effects of cannabis on health: an update of the literature since 1996.

Recent research has clarified a number of important questions concerning adverse effects of cannabis on health. A causal role of acute cannabis intoxication in motor vehicle and other accidents has now been shown by the presence of measurable levels of Delta(9)-tetrahydrocannabinol (THC) in the blood of injured drivers in the absence of alcohol or other drugs, by surveys of driving under the influence of cannabis, and by significantly higher accident culpability risk of drivers using cannabis. Chronic inflammatory and precancerous changes in the airways have been demonstrated in cannabis smokers, and the most recent case-control study shows an increased risk of airways cancer that is proportional to the amount of cannabis use. Several different studies indicate that the epidemiological link between cannabis use and schizophrenia probably represents a causal role of cannabis in precipitating the onset or relapse of schizophrenia. A weaker but significant link between cannabis and depression has been found in various cohort studies, but the nature of the link is not yet clear. A large body of evidence now demonstrates that cannabis dependence, both behavioral and physical, does occur in about 7-10% of regular users, and that early onset of use, and especially of weekly or daily use, is a strong predictor of future dependence. Cognitive impairments of various types are readily demonstrable during acute cannabis intoxication, but there is no suitable evidence yet available to permit a decision as to whether long-lasting or permanent functional losses can result from chronic heavy use in adults. However, a small but growing body of evidence indicates subtle but apparently permanent effects on memory, information processing, and executive functions, in the offspring of women who used cannabis during pregnancy. In total, the evidence indicates that regular heavy use of cannabis carries significant risks for the individual user and for the health care system.

Accidents, Traffic↗
PubMed2001

Early clinical manifestations of cannabis dependence in a community sample.

BACKGROUND: In this research, the 'natural history' of cannabis dependence is probed, using data from a large epidemiological sample of cannabis users followed from 1981 through 1996, until most of these users had passed through the empirically derived period of risk for developing cannabis dependence. METHODS: The Baltimore Epidemiologic Catchment Area research group sampled, recruited, and assessed 3481 adults age 18+ years in 1981. Survivors were re-assessed roughly 13 years later. Among 599 cannabis users, a total of 37 had become cases of cannabis dependence during the follow-up interval; 41 had developed DSM-IIIR cannabis abuse without dependence; 521 had suffered insufficient problems to qualify as cases. Survival analysis methods were used to plot and study the cumulative occurrence of these problems in a primary contrast of the 37 dependence cases and 562 non-cases. RESULTS: Subjectively felt loss of control over cannabis and continued cannabis use despite knowledge of harm seem to appear most rapidly among cases of cannabis dependence. In contrast, subjectively felt withdrawal symptoms tended to emerge later and for a much smaller proportion of dependence cases and non-cases. CONCLUSION: The 5000+ person-years of follow-up experience provided by the cannabis users in this study give an unprecedented look at the natural history and clinical course of cannabis dependence. Distinctive features of early cannabis dependence may help differentiate cannabis users who progress to clinically significant dependence from those who remain non-dependent.

Adolescent↗
PubMed2001

The natural course of cannabis use, abuse and dependence over four years: a longitudinal community study of adolescents and young adults.

OBJECTIVES: To determine incidence and patterns of natural course of cannabis use and disorders as well as cohort effects in a community sample of adolescents and young adults. METHOD: Cumulative incidence and patterns of cannabis use and disorders were examined in a prospective longitudinal design (mean follow-up period=42 months) in a representative sample (N=2446) aged 14-24 years at the outset of the study. Patterns of cannabis use, abuse and dependence (DSM-IV) were assessed with the Composite International Diagnostic Interview (M-CIDI). RESULTS: (1) Cumulative lifetime incidence for cannabis use (at second follow-up): 47%; 5.5% for cannabis abuse, 2.2% for dependence. (2) Men used and abused cannabis more often than women. (3) The majority of the older participants (18-24 years at baseline) had reduced their cannabis use at follow-up, while younger participants (14-17 years at baseline) more often had increased their use and developed abuse or dependence. (4) The younger birth cohort (1977-1981) tended to start earlier with substance (ab)use compared to the older birth cohort (1970-1977). (5) Cannabis use was associated with increasing rates of concomitant use of other licit and illicit drugs. CONCLUSIONS: Cannabis use is widespread in our sample, but the probability of developing cannabis abuse or dependence is relatively low (8%). The natural course of cannabis use is quite variable: about half of all cannabis users stopped their use spontaneously in their twenties, others report occasional or more frequent use of cannabis.

Adolescent↗
PubMed2001

Cannabis use and dependence among Australian adults: results from the National Survey of Mental Health and Wellbeing.

AIMS: To examine: (i) the prevalence of cannabis use and DSM-IV cannabis dependence among Australian adults, and (ii) correlates of level of cannabis involvement. DESIGN: Cross-sectional survey assessing substance use and DSM-IV substance use disorders (abuse and dependence). Setting and participants. A household survey of a nationally representative sample of 10 641 Australians aged 18 years and older. MEASUREMENTS: Trained interviewers administered a structured, modified version of the Composite International Diagnostic Interview (CIDI). FINDINGS: In the past 12 months, 2.2% (95%CI:1.8, 2.6) of adults were diagnosed with DSM-IV cannabis use disorder, comprising cannabis dependence (1.5%; 95%CI: 1.2, 1.8) and cannabis abuse (0.7%, 95%CI: 0.6, 0.8). Almost one-third of cannabis users (31.7%; 95%CI: 27.7, 35.7) met criteria for cannabis dependence (21%; 95%CI: 16.7, 25.3) and abuse (10.7%; 95%CI: 8.0, 13.4). Multinomial logistic regression revealed that compared to non-dependent cannabis users, non-users were more likely to be female, aged 25 + years, out of the labour force and married/de facto, and displayed lower levels of co-morbidity. In contrast, dependent cannabis users were more likely to be 18-24 years old, unemployed, and displayed higher levels of co-morbidity than non-dependent users. CONCLUSIONS: Cannabis use disorders affect approximately 300 000 Australian adults. A better understanding of the factors associated with cannabis dependence may help identify groups who have difficulties controlling use and aid the development of strategies for reducing cannabis-related harm.

Adolescent↗
PubMed2003

Exploring the association between cannabis use and depression.

AIM: To examine the evidence on the association between cannabis and depression and evaluate competing explanations of the association. METHODS: A search of Medline, Psychinfo and EMBASE databases was conducted. All references in which the terms 'cannabis', 'marijuana' or 'cannabinoid', and in which the words 'depression/depressive disorder/depressed', 'mood', 'mood disorder' or 'dysthymia' were collected. Only research studies were reviewed. Case reports are not discussed. RESULTS: There was a modest association between heavy or problematic cannabis use and depression in cohort studies and well-designed cross-sectional studies in the general population. Little evidence was found for an association between depression and infrequent cannabis use. A number of studies found a modest association between early-onset, regular cannabis use and later depression, which persisted after controlling for potential confounding variables. There was little evidence of an increased risk of later cannabis use among people with depression and hence little support for the self-medication hypothesis. There have been a limited number of studies that have controlled for potential confounding variables in the association between heavy cannabis use and depression. These have found that the risk is much reduced by statistical control but a modest relationship remains. CONCLUSIONS: Heavy cannabis use and depression are associated and evidence from longitudinal studies suggests that heavy cannabis use may increase depressive symptoms among some users. It is still too early, however, to rule out the hypothesis that the association is due to common social, family and contextual factors that increase risks of both heavy cannabis use and depression. Longitudinal studies and studies of twins discordant for heavy cannabis use and depression are needed to rule out common causes. If the relationship is causal, then on current patterns of cannabis use in the most developed societies cannabis use makes, at most, a modest contribution to the population prevalence of depression.

Adolescent↗
PubMed2000

Cannabis use and psychosis: a review of clinical and epidemiological evidence.

OBJECTIVE: This paper evaluates evidence for two hypotheses about the relationship between cannabis use and psychosis: (i) that heavy cannabis use causes a 'cannabis psychosis', i.e. a psychotic disorder that would not have occurred in the absence of cannabis use and which can be recognised by its pattern of symptoms and their relationship to cannabis use; and (ii) that cannabis use may precipitate schizophrenia, or exacerbate its symptoms. METHOD: Literature relevant to drug use and schizophrenia is reviewed. RESULTS: There is limited clinical evidence for the first hypothesis. If 'cannabis psychoses' exist, they seem to be rare, because they require very high doses of tetrahydrocannabinol, the prolonged use of highly potent forms of cannabis, or a preexisting (but as yet unspecified) vulnerability, or both. There is more support for the second hypothesis in that a large prospective study has shown a linear relationship between the frequency with which cannabis had been used by age 18 and the risk over the subsequent 15 years of receiving a diagnosis of schizophrenia. CONCLUSIONS: It is still unclear whether this means that cannabis use precipitates schizophrenia, whether cannabis use is a form of 'self-medication', or whether the association is due to the use of other drugs, such as amphetamines, which heavy cannabis users are more likely to use. There is better clinical and epidemiological evidence that cannabis use can exacerbate the symptoms of schizophrenia.

Adolescent↗
PubMed2007

Negative consequences associated with dependence in daily cannabis users.

BACKGROUND: Cannabis is the most widely consumed illicit substance in America, with increasing rates of use. Some theorists tend to link frequency of use with cannabis dependence. Nevertheless, fewer than half of daily cannabis users meet DSM-IV-TR criteria for cannabis dependence. This study seeks to determine whether the negative aspects associated with cannabis use can be explained by a proxy measure of dependence instead of by frequency of use. RESULTS: Over 2500 adult daily cannabis users completed an Internet survey consisting of measures of cannabis and other drug use, in addition to measures of commonly reported negative problems resulting from cannabis use. We compared those who met a proxy measure of DSM-IV-TR criteria for cannabis dependence (N = 1111) to those who did not meet the criteria (N = 1770). Cannabis dependent subjects consumed greater amounts of cannabis, alcohol, and a variety of other drugs. They also had lower levels of motivation, happiness, and satisfaction with life, with higher levels of depression and respiratory symptoms. CONCLUSION: Although all of our subjects reported daily use, only those meeting proxy criteria for cannabis dependence reported significant associated problems. Our data suggest that dependence need not arise from daily use, but consuming larger amounts of cannabis and other drugs undoubtedly increases problems.

Adolescent↗
PubMed1998

Cannabis dependence, withdrawal, and reinforcing effects among adolescents with conduct symptoms and substance use disorders.

The prevalence of cannabis use is rising among adolescents, many of whom perceive little risk from cannabis. However, clinicians who treat adolescent substance users hear frequent reports of serious cannabis-use disorders and problems. This study asked whether cannabis produced dependence and withdrawal among such patients, and whether patients' reports supported previous laboratory findings of reinforcing effects from cannabis. This was a screening and diagnostic study of serial treatment admissions. The diagnostic standard was the DSM-III-R dependence criteria, and the setting was a university-based adolescent substance treatment program with male residential and female outpatient services. The patients were 165 males and 64 females from consecutive samples of 255 male and 85 female 13-19-year-olds referred for substance and conduct problems (usually from social service or criminal justice agencies). Eighty-seven patients were not evaluated, usually due to early elopement. Twenty-four others did not meet study admission criteria: > or = one dependence diagnoses and > or = three lifetime conduct-disorder symptoms. The main measures were items from diagnostic interview instruments for substance dependence, psychiatric disorders, and patterns of substance use. Diagnoses were substance dependence, 100%; current conduct disorder, 82.1%; major depression, 17.5%; attention-deficit/hyperactivity disorder, 14.8%. The results show that most patients claimed serious problems from cannabis, and 78.6% met standard adult criteria for cannabis dependence. Two-thirds of cannabis-dependent patients reported withdrawal. Progression from first to regular cannabis use was as rapid as tobacco progression, and more rapid than that of alcohol, suggesting that cannabis is a reinforcer. The data indicate that for adolescents with conduct problems cannabis use is not benign, and that the drug potently reinforces cannabis-taking, producing both dependence and withdrawal. However, findings from this severely affected clinical population should not be generalized broadly to all other adolescents.

Adolescent↗
PubMed2007

Effects of co-occurring cannabis use disorders on the course of bipolar disorder after a first hospitalization for mania.

CONTEXT: Cannabis use disorders commonly co-occur in bipolar disorder; however, the effects of cannabis abuse on outcome have been minimally studied. OBJECTIVE: To identify how the sequence of the onsets of a cannabis use disorder and bipolar disorder is associated with the subsequent course of each condition. DESIGN: Inception cohort. SETTING: Academic medical center. PATIENTS: Patients (N = 144) were studied who met criteria for bipolar I disorder (manic or mixed), were 12 to 45 years old, and had no previous hospitalizations and minimal previous treatment. Patients were followed up for up to 5 years and included 33 in whom the onset of a cannabis use disorder preceded the onset of bipolar disorder (cannabis first), 36 in whom bipolar disorder onset preceded the onset of cannabis abuse (bipolar first), and 75 with bipolar disorder only. MAIN OUTCOME MEASURES: Symptomatic recovery and recurrence of both conditions and percentage of follow-up time with affective and cannabis use disorder symptoms. RESULTS: The cannabis first group exhibited better recovery than the other groups, although when adjusted for potential mediator variables these results did not persist. Cannabis use was associated with more time in affective episodes and with rapid cycling. Most cannabis use disorders remitted immediately after hospitalization, followed by rapid rates of recurrence. CONCLUSIONS: The effects of the sequence of onsets of bipolar and cannabis use disorders were less pronounced than observed in co-occurring alcohol and bipolar disorders. Aggressive drug abuse treatment immediately after a first psychiatric hospitalization might decrease rates of recurrence and new cases of cannabis use disorder in the course of bipolar disorder.

Adolescent↗
PubMed2006

Duration of cannabis use--a novel phenotype?

Although cannabis is the most commonly used illicit drug, duration of cannabis use is typically short, with many of those who initiate cannabis use ceasing use by their late twenties. In this paper we analyze data from a volunteer Australian cohort of 6265 male and female twins to examine whether the duration of cannabis use is an informative phenotype for future genetic analyses. Genetic modeling indicated: (a) moderate genetic influences on duration of cannabis use in both males (41%; 95% CI=31-51) and females (55%; 95% CI=46-63); (b) strong genetic influences on cannabis dependence in both males (72%, 95% CI=61-81) and females (62%, 95% CI=48-74); (c) no evidence of shared environmental influences on duration of cannabis use or on cannabis dependence in either males or females. Importantly, this model fitting indicated that a substantial component of genetic influences (rg=.90, 95% CI=.77-.99 (males); .70, 95% CI=.57-.83 (females)) on duration of cannabis use was shared with those influencing liability to cannabis dependence. While there were high genetic correlations in both women and men, lifetime duration of cannabis may be uniquely informative in assessing components of liability to cannabis use.

Adult↗
PubMed2001

Reducing the harms caused by cannabis use: the policy debate in Australia.

The debate about cannabis policy in Australia has revolved around the harms that cannabis causes to users and the community, on the one hand, and the harms that are caused by the prohibition of its use, on the other. This paper assesses evidence on: (1) the harms caused to users and the community by cannabis use (derived from the international scientific literature) and (2) the harms that arise from prohibition (as reflected in Australian research). The most probable harms caused by cannabis use include: an increased risk of motor vehicle accidents; respiratory disease; dependence; adverse effects on adolescent development; and the exacerbation of psychosis. The harms of the current prohibition on cannabis use policy are less tangible but probably include: the creation of a large blackmarket; disrespect for a widely broken law; harms to the reputation of the unlucky few cannabis users who are caught and prosecuted; lack of access to cannabis for medical uses; and an inefficient use of law enforcement resources. Cannabis policy unavoidably involves trade offs between competing values that should be made by the political process. Australian cannabis policy has converged on a solution which continues to prohibit cannabis but reduces the severity of penalties for cannabis use by either removing criminal penalties or diverting first time cannabis offenders into treatment and education.

Adolescent↗
PubMed2003

Screening for cannabis use disorders in an adolescent emergency department sample.

Cannabis, more often than alcohol, is the drug mentioned in substance-related reasons for treatment of an adolescent in an emergency department (ED). This study examined the prevalence of DSM-IV cannabis and alcohol diagnoses in an adolescent ED sample, evaluated the performance (i.e. sensitivity and specificity) of DSM-IV cannabis symptoms and other screening items as indicators of cannabis diagnosis status, and examined parent-adolescent agreement on the presence of cannabis and alcohol diagnoses. Adolescents (ages 13-19, n=442) admitted to an ED for a non-substance-related injury were administered the diagnostic interview schedule for children (DISC). Parents (n=272) of adolescents younger than age 18 completed the DISC-parent version to report on their child's drug use. A minority met criteria for a current DSM-IV cannabis or alcohol diagnosis: 7.9% for both alcohol and cannabis, 7.5% for cannabis-only, and 9.0% for alcohol-only. Frequency of cannabis use had the best overall performance in discriminating those with and without a cannabis diagnosis compared with items on perceived risk of cannabis use, peer cannabis use, and alcohol and cigarette use. Parent reports generally underestimated the adolescent's substance use. Questions on level of substance use generally provide an efficient method of screening adolescents for substance-related problems in an ED setting.

Adolescent↗
PubMed2006

Cannabis use disorders in the USA: prevalence, correlates and co-morbidity.

BACKGROUND: The purpose of this study was to present 12-month and lifetime estimates of the prevalence, sociodemographic and clinical correlates, and psychiatric co-morbidity of DSM-IV cannabis abuse and dependence. METHOD: Data were derived from a large nationally representative survey (n=43093) of US adults. RESULTS: The prevalence of 12-month and lifetime DSM-IV cannabis abuse (1.1% and 7.2%) exceeded the corresponding rates of cannabis dependence (0.3% and 1.3%). Being male, Native American, widowed/separated/divorced, and residing in the West increased the odds whereas being Black, Asian or Hispanic decreased the odds of cannabis abuse and dependence. Cannabis dependence was significantly associated with low income. Ages of onset for both cannabis use disorders occurred in adolescence and the majority of individuals with these disorders remained untreated. Co-morbidity was high between cannabis use disorders and other Axis I and II disorders. CONCLUSIONS: Cannabis use disorders continue to present a widespread and serious personal and public health problem. Native Americans were found to have high rates of cannabis use disorders, warranting closer attention to the mental health needs of this subgroup. Associations between cannabis abuse and dependence and Axis I and II disorders were strong, signaling the need for more comprehensive assessment of individuals with cannabis use disorders. Further controlled treatment studies are needed, especially among co-morbid individuals, in view of growing evidence of the adverse personal, medical and societal impacts of cannabis use disorders in the USA.

Adolescent↗
PubMed2004

Emerging patterns of cannabis and other substance use in Aboriginal communities in Arnhem Land, Northern Territory: a study of two communities.

A recent rise in cannabis use in Indigenous communities in northern Australia may have compounded existing patterns of other substance use. This paper describes these patterns in Arnhem Land in the 'Top End' of the Northern Territory (NT). Economic impacts of the cannabis trade are also described. In a descriptive cross-sectional study, random samples included 336 people (169 males, 167 females) aged 13 - 36 years. Consensus classification of lifetime and current use of cannabis, alcohol, tobacco, kava, inhalants (petrol) and other drugs was derived based on health workers' proxy assessments. A sample (n = 180, aged 13 - 36) was recruited opportunistically for interview. Lifetime cannabis users among those interviewed (n = 131, 81 males, 50 females) described their current cannabis use, usual quantities purchased and consumed, frequency and duration of cannabis use and other substance use. In the random samples, 69% (63 - 75%) of males and 26% (20 - 31%) of females were lifetime cannabis users (OR = 7.4, 4.5 - 12.1, p < 0.001). The proportion of males currently using cannabis was 67% (60 - 73%) while the proportion of females currently using cannabis was 22% (16 - 27%) (OR = 7.9, 4.8 - 13.1, p < 0.001). Current cannabis users were more likely than non-users to be also using alcohol (OR = 10.4, 4.7 - 23.3, p < 0.001), tobacco (OR = 19.0, 7.9 - 45.8, p < 0.001) and to have sniffed petrol (OR = 9.1, 4.6 - 18.0, p < 0.001) but were less likely to be using kava (OR = 0.4, 0.2 - 0.9, p < 0.001). Among those interviewed, higher tobacco consumption in current users and greater alcohol use in lifetime users was associated with increased cannabis use. Action is required to reduce cannabis use, especially in combination with other substances.

Adolescent↗
PubMed2005

Limited use of medicinal cannabis but for labeled indications after legalization.

Since September 2003, cannabis is available for medicinal purposes in Dutch pharmacies to. It was anticipated that the medicinal cannabis use via illegal ways would decrease. The objective of this study was to get insight in the use of medicinal cannabis in daily practise as dispensed by community pharmacies and to characterize the users as well as the symptoms and conditions cannabis is prescribed for.A prospective follow-up study among 200 patients who filled a prescription for medicinal cannabis was performed in the period between September 2003 and January 2004. The patients filled out a structured questionnaire concerning symptoms and conditions and their experience with cannabis. Of all patients, 42% suffered from multiple sclerosis, 11% suffered from rheumatic diseases, and 60% of respondents already used cannabis before the legalization. Cannabis was mainly used for chronic pain and muscle cramp/stiffness.The indication of medicinal cannabis use was in accordance with the labeled indications. However, more than 80% of the patients still obtained cannabis for medicinal purpose from the illegal circuit. Because of the higher prices in pharmacies, ongoing debate on the unproven effectiveness of the drug and the hesitation by physicians to prescribe cannabis.

Cannabis↗
PubMed2000

Cannabis (hemp) positive skin tests and respiratory symptoms.

BACKGROUND: We have noted several patients who had rhinitis and/or asthma symptoms when exposed to Cannabis plants in the summer months. Cannabis plants are common in the Midwest. OBJECTIVES: To examine whether Cannabis might be a clinically important allergen, we determined Cannabis pollination patterns in the Omaha area for 5 years, the prevalence of skin test positivity, and the association with respiratory symptoms. METHODS: Airborne Cannabis (and other weed) pollens were collected using a Rotorod air impactor, and pollen counts were done using a standardized protocol. RESULTS: Measurable Cannabis pollen count was not recorded until the last 2 weeks of July. Peak pollination typically occurred during mid- to late-August, and comprised up to 36% of the total pollen counts. Cannabis pollen was not observed after mid-September. To determine the prevalence of skin test positivity, we added Cannabis to the multi-test routine skin test battery. Seventy-eight of 127 patients tested (61%) were skin test positive. Thirty of the 78 patients were randomly selected to determine if they had allergic rhinitis and/or asthma symptoms during the Cannabis pollination period. By history, 22 (73%) claimed respiratory symptoms in the July through September period. All 22 of these subjects were also skin test positive to weeds pollinating during the same period as Cannabis (ragweed, pigweed, cocklebur, Russian thistle, marsh elder, or kochia). CONCLUSIONS: The strong association between skin test reactivity, respiratory symptoms, and pollination period suggests that Cannabis could be a clinically important aeroallergen for certain patients and should be further studied.

Air Pollutants↗