The overwhelming majority of this sample reported using cannabis to treat multiple health conditions. This result is unsurprising given increased cultural attention to the wide range of conditions for which cannabinoids may be therapeutic. However, panacea-like use may prove problematic. The same cannabinoid preparation that might be helpful for one condition [e.g., high THC and neuropathic pain ] could exacerbate symptoms of another [e.g., high THC and anxiety ]. Indeed, the current study found limited variability in choice of cannabinoid content; the overwhelming majority of veterans preferred cannabis with high THC relative to CBD. This quantity and frequency of use are consistent with other populations of medicinal cannabis users. For example, Bonn-Miller et al. documented average rates of cannabis use of 2–3 times per day, consuming between 6 and 12 grams of cannabis per week, in a general sample of medicinal cannabis users. The sample’s strong preference for frequent use of high THC-containing cannabis raises concerns for long-term outcomes of self-medication. While THC-rich cannabis may provide acute relief for symptoms often experienced by veterans [e.g., nightmares ],metal greenhouse benches it is also more likely to cause intoxication and associated with increased risk of developing symptoms of CUD relative to CBD-rich cannabis . Indeed, CBD may reduce anxiety , depression , and inflammation , as well as improve cognition and extinction learning .
This dichotomy could explain why veterans who use cannabis to self-treat mental health symptoms, like PTSD, often show worse long-term outcomes and report higher rates of problematic use , despite preclinical and human experimental evidence of potential therapeutic utility of certain cannabinoids. Likewise, while the majority of participants preferred using an inhalation method for administration of cannabinoids, a nontrivial number reported that they prefer highly concentrated “dabs” , which is associated with greater risk of tolerance and withdrawal . Moreover, those who typically chose an inhalation method of administration reported a strong preference for smoking cannabis over vaporization. Smoking cannabis carries significantly greater health risks compared to vaporization . Perhaps more troubling is the finding that over 40% of the sample either didn’t know or didn’t care what type of cannabis they were using. This may be a function of the lack of sufficient science and education within this space. Given the historic barriers to conducting well-controlled trials with cannabinoids, even savvy patients have limited information to inform their choice of cannabinoid product, which might lead patients to choose at random. Moreover, while it is likely that many providers are rightly hesitant to make recommendations without the results of well-controlled clinical trials, there is also an enormous gap in the knowledge and training of those who interface with patients in terms of best practices given the current evidence base .
The primary limitation of the current study is that it assessed cannabis use and related behaviors entirely using self-report with no ability to verify cannabinoid constituents in products typically used. This is a major limitation of the current study because there is large variability in cannabinoid content within “strains” . Oversight of non-FDA approved cannabinoid products is lacking, and recent reports suggest that many of these products are often mislabeled . However, current legal prohibitions made collection and objective testing of participants’ products impossible. While using product names to assess preferred cannabinoid ratio provides only a gross approximation of possible cannabinoid content, the results of the current study offer more information on choice of cannabinoid products among veterans than exist in the literature to date. Substitution behavior was also assessed through self-report and was assessed broadly by asking participants if they had ever substituted cannabis for other substances. Substitution, however, can occur in a multitude of ways. It is unclear whether veterans who endorsed substitution were completely abstaining from the substance that they endorsed substituting cannabis for, or whether they interpreted substitution as reduction of quantity or frequency of use. Likewise, retrospective recall of substance use is often inaccurate . Substitution data collected via self-report might not reflect these veterans’ true behavior. Finally, the current study did not collect data on age of first initiation of use of these other substances. It is unclear whether these participants started using these substances before or after initiation of cannabis use, and whether substitution behaviors co-varied with combat exposure or other military-related experiences.
Despite these limitations, the current study’s findings highlight an ongoing issue among veterans, namely the possible gravitation toward addictive substances that provide acute relief yet potential long-term exacerbation of symptoms . Coupled with the need for improved science in this domain, findings highlight the importance of training providers in the nuances and differential effects of specific cannabinoids, as well as steering patients toward cannabinoid-based products that, while less rewarding in the short term, may be associated with reduced risk and long-term therapeutic gains. Future research might focus on the development of interventions that disseminate information on cannabis and cannabinoids to providers and patients. For example, vaporization of flower cannabis is associated with significantly lower risks of bronchial symptoms compared to combusted cannabis , but a very small proportion of this sample noted that they preferred vaporization to other inhalation methods. This suggests one specific target for possible intervention. The current study also confirms the findings of previous studies that have documented a trend in substitution behavior, where cannabis is substituted for other drugs, which, if associated with reduced harm, could be beneficial for overall health. Future studies might attempt to categorize which specific medications veterans who use medicinal cannabis are substituting cannabinoids for and whether those changes are associated with improvements in functioning. Cannabis sativa L. is a dioecious plant, producing male and female flowers on separate unisexual individuals . Although both male and female plants are capable of producing cannabinoids in equal concentrations , female plants produce greater floral biomass than male plants and thus are exclusively used in commercial marijuana production facilities. Moreover, after pollination, female plants alter their relative investment in phytochemicals by reducing the production of secondary metabolites like cannabinoids, flavonoids, and terpenoids . In the absence of pollen, stigmas on female plants continue to grow and thus produce more surface area on which cannabinoids can be produced . Because of this negative impact of pollination on cannabinoid yield, industrial growers rarely maintain male plants in production facilities, and instead propagate their stock of female plants by vegetative cloning . However, the “mother” plants used to produce clones eventually become non-regenerative and new mother plants are grown from seed, which necessitates pollination . Therefore, careful consideration must be given as to the most effective and efficient ways to collect pollen for controlled crosses while preventing pollen escape into production areas. Cannabis is anemophilous ,rolling greenhouse tables and therefore relies on air movement for pollen transfer from male to female plants, sometimes across long distances . Pollen dispersal mechanisms often reflect pollen ornamentation, as seen in C. sativa’s smooth exine layer, triporate morphology, and low mass—features intended to maximize pollen dispersal distance and chance of successful ovule fertilization . The aerodynamic morphology of C. sativa’s pollen highlights the difficulty associated with controlling its movement, as any airflow following anther dehiscence can result in pollen movement, a frequent issue when studying dispersal in anemophilous species .
It is therefore important to determine the most efficient method of capturing wind borne pollen upon anthesis, in terms of both the number of pollen grains collected and the time spent collecting pollen. Procedures for controlled pollen capture are typically required in crop breeding programs to ensure precise knowledge of paternity so as to breed progeny with preferred traits . For example, standard methods for maize breeding were established in the early 1900s, with an abundance of literature outlining the procedure for controlled crosses . However, because corn is monecious, breeding procedures prioritize avoidance of self-fertilization , with controlled capture of pollen samples as a secondary goal . Studies on controlled pollen capture in other species have developed methods based on species-specific traits, such as the clipping of large anthers in Eucalyptus L’Hér. . Although some literature related to maximizing pollen capture from trees describes methods that may be applied to cannabis , these would require modification based on the scale of collection and organismal size. In addition, most research on determining optimal methods for controlled pollination relates to pollen storage and germination conditions rather than optimizing controlled pollen capture. One of the largest barriers to comparing the efficiency of pollen collection methods is quantifying relative pollen yield. Previous research on pollen production in cannabis, which estimated the number of pollen grains per anther, relied on hemocytometers , a method frequently employed for counting pollen grains . More broadly, light scattering as a method for rapidly estimating particle abundance is well documented , and laser scattering has been used to analyze the physical properties of pollen grains . Relative to direct pollen counting using a hemocytometer, visible light spectroscopy could allow for the rapid quantification of particles in a liquid suspension. Here, we compared several existing methods used to collect pollen in other species, i.e., hand collection , vacuum collection , bag collection , and water collection , and explored their use in cannabis. Notably, we could not find any peer-reviewed publications that directly compared the efficiency of such methods , although many have examined pollen collection using a single methodology . Collecting pollen in large quantities may be of use in commercial crop breeding programs, especially when creating a repository of genetic stock for later use, and as such, we were interested in both the relative yield and efficiency of various methods. Hand collection, while simple in practice, may be inefficient because, in cannabis, it relies on pollen removal from individual flowers, one by one. Comparatively, vacuum collection may be more efficient but could be prone to sample contamination if male plants are not properly isolated from each other. Bag collection, similar to vacuum collection, is efficient, but the plant must be able to hold up bags; in the case of cannabis, male plants are so diminutive, and the flowers are so dispersed on a plant, that this is a difficult endeavor . Bag collection also could result in reduced yield if issues such as static charge of pollen grains are not sufficiently addressed .We used two hemp cultivars of C. sativa , both possessing an expected total tetrahydrocannabinol content of less than 0.01%; we grew CFX-1 in the first trial and CFX-2 in the second trial . Following germination in a two-tier terracotta germination pot , which took three days, we planted the seedlings in SC-10 containers filled with 200 mL of PRO-MIX BX mycorrhizae peat moss growing medium . A week later, we transplanted seedlings into 1-L pots filled with the same growing medium. We applied 250 mL of filtered water twice weekly and applied 250 mL of 0.4% diluted Miracle-Gro once weekly. For four weeks, plants grew under 24-h lighting from high-pressure sodium fixtures . Male floral development was visible in the third week, and we selected early-flowering males for use in our experiments to minimize variability in the number of inflorescences on each plant. We pruned the apical meristems of male plants twice, once in week 3 and once in week 4, to promote increased branching and thus inflorescence growth. After approximately four weeks, we switched plants to 12-h lighting to induce anthesis under visible spectrum LED fixtures .In the first trial, we used three pollen collection methods : hand collection , bag collection, and water collection . In the second trial, we maintained hand collection as a control and tested vacuum collection. To compare the yield and efficiency of collection methods, we imposed each pollen collection treatment on a randomly selected subset of experimental plants, each of which we collected three times during the course of the trial. Cannabis anthers dehisce non-concurrently, and as such we initiated pollen collection when at least 33% of visible male flowers were releasing pollen to ensure there was enough pollen to collect in the context of a breeding program. From each plant, we performed three collections over a seven-day period, where initial sufficient anther dehiscence occurred on day zero, the first collection occurred on day 1, and subsequent collections on days 4 and 7. In our first trial, we attempted to perform a fourth collection on day 10 but found that by this point the plants were no longer producing enough pollen to warrant a fourth collection from that point onward.