The current study did not examine variability in sleep patterns and sleep problems that may be particularly salient to MC users.Additional research in this area is needed to better inform treatment interventions.Meanwhile, treatments such as cognitive– behavioral therapy for insomnia should be routinely available to veterans who may derive greater benefit from this behavioral strategy than resorting to using cannabis with its known adverse effects on health, cognitive, and psychological functioning.Finally, VHA providers should expect an increase in the number of veterans seeking voluntary treatment for CUD, because more cannabis users now seek treatment since the legalization of MC use.Therefore, routine screening or assessment for cannabis use and CUD in the VHA is recommended, particularly in the context of assessing for sleep problems and trauma related symptoms.At a minimum, researchers and clinicians should not be combining cannabis use with other illicit drugs of abuse in terms of screening and treatment recommendations.Several study limitations warrant mention.As with many veteran samples, a small number of female veterans limited the generalizability of our findings to female veterans who are using the VHA for health care services.The caveat to our and other similar cross-sectional findings is that these data cannot establish precedence of cannabis versus other substances or whether MC use leads to subsequent reductions in alcohol or other illicit or prescribed substances, or whether sleep problems amount to increased MC use or vice versa.Planned longitudinal analyses of the larger parent study will indeed help clarify the putative relationship between these variables and MC use in this veteran sample.Next, characterizing MC and RC groups as mutually exclusive categories does not take into account the nuance and complexity of using cannabis for reasons that can be viewed as both medicinal and recreational.Future studies might need to utilize a continuous index of the proportion of use for medicinal and recreational purposes and account for differences across states and jurisdictions in their definitions of medical use of cannabis.

Next, it is possible that responding to the questionnaires specific to medicinal cannabis grow set up use could have influenced responses on the subsequent MPS assessing cannabis-related problems for the MC users.Finally, the study was explicitly focused on examining differences between MC and RC users in terms of the presence of PTSD and MDD diagnoses, the two psychiatric disorders that are most prevalent among the returning veterans.However, comorbidity with other anxiety disorders may be important to investigate in future comparisons between MC and RC users.In conclusion, our findings suggest research on MC use in veterans needs to continue.In addition, although the line between cannabis use for medicinal and recreational reasons may often be blurred , current findings help identify motivations underlying medicinal cannabis use among veterans.Future research can further resolve and address specific needs of veterans seeking medicinal cannabis, which could inform mental health treatment within the VHA.Legalization of cannabis production in 2017 has generated demands for state regulatory, research and extension agencies, including UC, to address the ecological, social and agricultural aspects of this crop, which has an estimated retail value of over $10 billion.Despite its enormous value and importance to California’s agricultural economy, remarkably little is known about how the crop is cultivated.While general information exists on cannabis cultivation, such as plant density, growing conditions, and nutrient, pest and disease management , only a few studies have attempted to measure or characterize some more specific aspects of cannabis production, such as yield per plant and regional changes in total production area.These data represent only a very small fraction of domestic or global activity and are likely skewed since they were largely derived not from field studies but indirectly from police seizure data or aerial imagery.In California, where approximately 66% of U.S.marijuana is grown , knowledge of the specific practices across the wide range of conditions under which it is produced is almost nonexistent.Currently, 30 U.S.states have legalized cannabis production, sales and/or use, but strict regulations remain in place at the federal level, where it is classified as a Schedule I controlled substance.As a land-grant institution, UC receives federal support; were UC to engage in work that directly supports or enhances marijuana production or profitability, it would be in violation of federal law and risk losing federal support.As a result, UC research on California cannabis production has been limited and focused on the geography of production and its environmental impacts.

These studies have documented the negative effects of production on waterways, natural habitats and wildlife.While such effects are not unique to cannabis agriculture per se, they do present a significant threat to environmental quality and sensitive species in the watersheds where cannabis is grown.Science-based best management practices to mitigate or avoid impacts have not been developed for cannabis.Because information on cannabis production practices is so limited, it is currently not possible to identify key points of intervention to address the potential negative impacts of production.As a first step toward understanding cannabis production practices, we developed a statewide survey on cultivation techniques, pest and disease management, water use, labor and regulatory compliance.The objective was to provide a starting point from which UC scientists could build research and extension programs that promote best management practices — which are allowable as long as their intended purpose is not to improve yields, quality or profitability.Survey results also establish a baseline for documenting changes in cultivation practices over time as legal cannabis production evolves in California.To characterize key aspects of cannabis production in California, we developed an anonymous online survey using Qualtrics survey software.A web-based survey that masked participants’ identity was determined to be the most suitable approach given that in-person interviews were limited by legal restrictions on UC researchers visiting cannabis farms, and mail or telephone surveys were constrained by the lack of any readily available mailing address or telephone contact information for most cannabis growers, who are understandably discrete with this information.Survey questions focused on operational features , pest and water management, labor, farm revenue and grower demographics.Two draft surveys were reviewed by a subset of cannabis growers to improve the relevance of the questions and terminology.A consistent critique was that the survey was too long and asked for too much detail, taking up to 2 hours to complete, and that such a large time commitment would significantly reduce the response.We therefore made the survey more concise by eliminating or rephrasing many detailed questions across various aspects of cannabis production.

The final survey included 37 questions: 12 opened and 25 structured.Structured questions presented either a list of answer choices or a text box to fill in with a number.Each list of answer choices included an “Other” option with a box for growers to enter text.Open-ended questions had a text entry box with no character limit.Condensing the survey to capture more respondents resulted in less detailed data, but the overall nature of the survey remained the same — a survey to broadly characterize multiple aspects of cannabis production in California.Data from the survey has supported and contextualized research by other scientists on specific aspects of cannabis production, such as water use , permitting , law enforcement , testing requirements , crop prices and perceptions of cannabis cultivation in the broader community.Recruitment of survey participants leveraged networks of California cannabis growers who had organized themselves for various economic and political purposes.These were a combination of county, regional and large statewide organizations, with many growers affiliating with multiple groups.We identified the organizations through online searches and social media and sent recruitment emails to their membership list-serves.The emails contained an explanation of the survey goals, a link to the survey website and a message from the grower organization that endorsed the survey and encouraged members to participate.The emails were sent in July 2018 to approximately 17,500 email addresses, although not all members of these organizations necessarily cultivated cannabis, and the organizations noted that their mailing lists somewhat overlapped the lists of other groups that we contacted.For these reasons, the survey population was certainly less than 17,500 individual cannabis growers, outdoor cannabis grow but because we were not able to view mailing lists nor contact growers directly, and because there are no comprehensive surveys of the number of cannabis farms in California, we could not calculate a response rate or evaluate the representativeness of the sample.Respondents were given until Aug.15, 2018, to complete the survey.All survey participants remained anonymous, and response data did not include any specific participant identifiers.Our survey, although of limited sample size, is the first known survey of California cannabis growers and provided insights into common forms of cultivation, pest and disease management, water use and labor practices.Since completing this survey, we have discussed and/or presented the survey results with representatives from multiple cannabis grower organizations, and they confirmed that the data were generally in line with production trends.Evident in the survey results, however, was the need for more data on grower cultivation practices before best management practices or natural resource stewardship goals can be developed.All growers monitored crop health, and many reported using a preventative management strategy, but we have no information on treatment thresholds used or the efficacy of particular sprays on cannabis crops.Likewise, the details of species-level pest and disease identification, natural enemy augmentation and sanitation efforts remain unclear.

Growers did not report using synthetic pesticides, which contrasts with findings from previous studies that documented a wide range of synthetic pesticide residues on cannabis.Product selection for cannabis is very limited due to a mixed regulatory environment that currently does not allow for the registration of any insecticide or fungicide for use specifically on cannabis , although growers are allowed to use products that are exempt from residue tolerance requirements, exempt from registration requirements or registered for a use that is broad enough to include cannabis.As such, it may be that in the absence of legally available chemical controls growers were choosing allowable, biologically derived products or alternative strategies such as natural enemy augmentation and sanitation.Our survey population was perhaps biased toward non-chemical pest management — the organizations we contacted for participant recruitment included some that were formed to share and promote sustainability practices.Or, it may be that respondents were reluctant to report using synthetic chemicals or products not licensed for cannabis plants.The only other published data on water application rates for cannabis cultivation in California we are aware of is from Bauer et al., who used estimates for Humboldt County of 6 gallons per day per plant for outdoor cultivation over the growing season.Grower reported estimates of cannabis water use in this survey were similar to this rate in the peak growing season , but was otherwise lower.Due to the small sample size, we cannot say that groundwater is the primary water source for most cannabis growers in California or that few use surface water diversions.However, Dillis et al.found similar results on groundwater being a major water source for cannabis growers, at least in northwest California.If the irrigation practices reported in our survey represent patterns in California cannabis cultivation, best management practices would be helpful in limiting impacts to freshwater organisms and ecosystems.For example, where groundwater pumping has timely and proximate impacts to surface waters, limiting dry season groundwater extraction by storing groundwater or surface water in the wet season may be beneficial , though this will likely require increases in storage capacity.The recently adopted Cannabis Cultivation Policy requires a mandatory dry season forbearance period for surface water diversions, though not for groundwater pumping.Our survey results indicate that the practical constraints on adding storage may be a significant barrier for compliance with mandatory forbearance periods for many growers.More in-depth research with growers and workers is needed to explore the characteristics of the cannabis labor force and the trajectory of the cannabis labor market, especially in light of legalization.Several growers commented on experiencing labor shortages, a notable finding given that recent market analyses of the cannabis industry suggest that labor compliance costs are the most significant of all of the direct regulatory costs for growers.Higher rates of licensing compliance among medium and large farms is not surprising given the likelihood that they are better able to pay permitting costs.Yet, that the majority of respondents indicated they had not applied for a license to grow cannabis, with over half noting some income from cannabis sales, indicates potentially significant effects if these growers remain excluded from the legalization process.