Survey of Washington State Clinicians Finds Majority Concerned About Cannabis and Mental Health

More than a decade after Washington State legalized recreational cannabis, the clinicians treating its residents say they are worried. A new survey published in the Substance Use & Addiction Journal found that more than half of 388 Washington healthcare professionals expressed strong concern about mental health risks from cannabis use [1]. Nearly 20% reported encountering cannabis-related adverse health events in patients two to three times per month [1].

But the same survey revealed a striking paradox: 65.9% of those clinicians reported having slight or no knowledge about how cannabis interacts with other medications, and 42.8% admitted limited understanding of cannabis-induced psychosis [1]. Nearly 75% said they wanted more training on screening and managing cannabis-related health problems [1].

The question hanging over these findings is whether clinician concern reflects a genuine clinical signal — or whether it reflects a knowledge gap being filled by alarm rather than evidence.

The Survey: What It Found and What It Didn't

The study, led by Beatriz Carlini, a research associate professor of psychiatry and behavioral sciences at the University of Washington School of Medicine, surveyed doctors, nurses, and other health care professionals between December 2024 and March 2025 [1]. The 20-question instrument asked about clinical experiences with patients suffering cannabis-related health problems since Washington legalized recreational use in 2012 [2].

Among the specific conditions clinicians reported encountering: 70% had treated patients with cannabis hyperemesis syndrome (a condition involving repeated cycles of severe nausea and vomiting), 65% identified cannabis use disorder, 63% saw anxiety related to cannabis use, and 53% identified psychosis or hallucinations — with 34% calling psychosis the most serious condition they observed [1].

Carlini noted that the researchers "could find no other research papers where clinicians in the United States are asked about treating cannabis-related adverse conditions," framing the study as a first-of-its-kind snapshot [2].

The survey has clear limitations. At 388 respondents, the sample is modest. The published accounts do not specify a response rate, which makes it difficult to assess selection bias — clinicians who have encountered cannabis-related problems may have been more motivated to respond. The study also did not measure whether adverse effects are actually increasing in Washington, though Carlini noted that literature from other regions suggests they likely are [1]. The survey was conducted through the University of Washington's Addictions, Drug & Alcohol Institute (ADAI), which runs the Cannabis Education & Research Program [3].

What the Science Says: Psychosis, Depression, and the Causation Problem

The strongest evidence linking cannabis to mental health harm involves psychosis. The EU-GEI study, a large multicenter investigation, found that daily cannabis use was associated with 3.2 times higher odds of first-episode psychosis compared to never-users [4]. That study estimated a population attributable fraction of 12.2% — meaning roughly one in eight cases of first-episode psychosis could theoretically have been prevented if high-potency cannabis were not available [4]. In cities with particularly high-potency markets, like Amsterdam, the estimated fraction rose to roughly 50% [4].

Source: OpenAlex

Data as of Jan 1, 2026CSV

However, establishing causation remains difficult. A 2024 review in Psychiatry Research characterized the cannabis-psychosis relationship as subject to "confounders" and noted that "large-scale population-based studies" often lack adjustment for biological, psychological, and social factors that may explain the association through other pathways [5]. The self-medication hypothesis — that people with emerging psychotic symptoms may use cannabis to cope — complicates the direction of the relationship.

For depression, the evidence is weaker and less consistent. A 2025 meta-analysis published in Psychological Medicine found an association between cannabis use and depressive symptoms, but the authors noted that fewer studies attempted to address non-causal explanations compared to the psychosis literature [6]. A cross-sectional analysis of Colorado cannabis users found that the relationship between frequency of use and depression or anxiety symptoms was mixed and sometimes contradictory [7].

For anxiety, meta-analytic evidence supports a correlation with cannabis use, but the most plausible explanation in several reviews is that anxiety predisposes individuals toward cannabis use as self-medication rather than the reverse [5].

A 2025 study reported by ScienceDaily found strong links between high-potency THC and psychosis or schizophrenia, while results for anxiety and depression were mixed [8]. THC potency has risen sharply: analysis of more than 38,000 cannabis samples seized by the DEA between 1995 and 2014 showed average THC content rising from 4% to 12%, and modern vaping cartridges can reach 80–90% THC concentration [9].

Adolescents, Heavy Users, and the Potency Question

Clinician concern appears most acute around younger users and high-potency products. Research published in JAMA Psychiatry found that adolescents who used high-potency cannabis weekly had 11 times greater risk of developing a psychotic disorder [10]. The adolescent brain is considered particularly vulnerable to THC because the prefrontal cortex — which governs decision-making, impulse control, and emotional regulation — is still developing [9].

Yet Washington's own data complicates the narrative that legalization has fueled a youth crisis. The 2023 Healthy Youth Survey, representing over 217,000 students in grades 6–12, found that past-30-day marijuana use among 10th graders dropped 58% since legalization — from 20.0% in 2010 to 8.4% in 2023 [11]. Among 8th graders, the decline was 61%, from 9.5% to 3.7% [11]. Among 12th graders, use fell 38% to 16.3% [11].

Source: Washington Healthy Youth Survey 2023

Data as of Jan 1, 2023CSV

These declines are consistent with national trends. The Marijuana Policy Project cites data across multiple legalization states showing that adult-use legalization corresponds with drops in teen use [12]. NORML's fact sheets reach similar conclusions [13].

For adults, the picture is different. Washington's adult cannabis use rose from 18% reporting recent use in 2011 to 30% in 2021 [14]. The increase in adult use, combined with the availability of higher-potency products, forms the basis for much of the clinical concern.

The Training Gap: When Concern Outruns Knowledge

The UW survey's most striking finding may not be the level of concern but the level of admitted ignorance. With 65.9% of respondents reporting minimal knowledge of drug interactions and 42.8% reporting limited understanding of cannabis-induced psychosis, the survey raises the question of whether clinician alarm is grounded in clinical evidence or shaped by anecdotal encounters and cultural attitudes [1].

This gap is not unique to Washington. A scoping review of medical cannabis education found that cannabis has not been integrated into most medical school curricula, even decades after the first states legalized medical use [15]. A survey of the Society of Cannabis Clinicians found that only one physician reported receiving cannabis education during medical school; most gained knowledge through conferences (71%), medical literature (64%), and websites (62%) [16]. Nearly 80% of pharmacy students surveyed said medical cannabis should be added to their curricula [17].

More than 80% of the UW survey respondents said they would be more likely to screen for cannabis use and intervene if they had established treatment protocols and more referral options [1]. The barrier, in other words, is not just knowledge but infrastructure.

The Steelman Case: Is Clinician Concern Overstated?

Researchers who study legalization's net effects offer a more nuanced picture than the headline findings suggest.

A study analyzed by the Centre for Economic Policy Research examined staggered adoption of medical and recreational marijuana laws across U.S. states using nationally representative survey data and the Kessler Psychological Distress Scale. The headline finding: "no evidence of an overall effect on mental health" from legalization [18]. But that finding masked divergent effects by age. Older adults (59+) saw reduced mental distress from medical marijuana laws — roughly a quarter fewer "bad mental health days" per year — driven by those with chronic conditions who appeared to benefit from therapeutic use [18]. Younger adults under 35, especially those aged 18–25, saw roughly half a day more of poor mental health per year under recreational legalization [18].

The Cato Institute's 2021 analysis of state marijuana legalizations found it "difficult to see any association between marijuana legalization and changes in suicide trends," and noted that a 2017 National Academy of Sciences review described the cannabis-psychosis relationship as "multidirectional and complex" [19].

Source: OpenAlex

Data as of Jan 1, 2026CSV

The academic literature on this question has exploded — over 6,500 papers on cannabis legalization and mental health have been published since 2011, peaking at nearly 1,200 in 2023 — yet the field remains far from consensus on causation [20].

Meanwhile, Washington's declining youth use rates [11] and the absence of a clear population-level mental health deterioration attributable to legalization undercut the most alarming interpretations of the clinician survey.

Policy: Potency Taxes, Warning Labels, and $500 Million in Revenue

Washington collects over $500 million annually in cannabis tax revenue through a 37% excise tax at the point of sale, plus state and local sales taxes that bring the total consumer burden to 47–50% [21]. That revenue creates both a policy toolkit and a political constraint: any regulation that meaningfully restricts the market could threaten a significant state funding source.

Several policy interventions are under active debate. House Bill 2433 would replace the flat 37% excise tax with fixed rates tied to product type, package size, and potency — effectively a potency-based tax designed to discourage high-THC products [22]. A separate bill, House Bill 1641, would increase the excise tax up to 65% on certain high-potency products [22]. During the 2026 legislative session ending March 12, efforts to increase cannabis taxes failed, alongside proposals that would have raised the tax burden on most legal products [23].

Warning labels represent a lower-cost intervention. The American Enterprise Institute published a report documenting cannabis warning label shortcomings across states [24]. A Washington Post opinion piece argued that any federal marijuana reclassification should include health warnings [25]. Washington does have warning requirements as part of its regulatory framework, but public health advocates argue they are insufficient given current evidence on potency and psychosis risk.

The UW survey itself points to a systems-level gap: clinicians said the most useful interventions would be standardized screening protocols and expanded referral networks, not necessarily product restrictions [1]. This aligns with the finding that more than 80% of respondents would screen more often if given the tools to do so.

Industry and Advocacy Responses

The Washington CannaBusiness Association (WACA) advocates for a "legal, quality-controlled and well-regulated taxed cannabis marketplace that keeps products out of the hands of children" [23]. The organization has focused its lobbying on opposing tax increases that it argues would push consumers back to the unregulated market — a position that carries weight given that illicit cannabis markets persist even in legal states.

Patient advocacy groups like Americans for Safe Access have argued that adult-use and hemp markets do not adequately serve patients' specific medicinal needs and have called for greater patient representation in policy discussions [26]. The organization's 2025 federal policy review noted ongoing gaps between recreational market priorities and medical patient access.

The cannabis industry's strongest counterargument to clinician concern rests on two pillars: first, that youth use has declined under legalization [11][12], contradicting predictions that legal access would increase adolescent consumption; and second, that the regulated market provides product testing, labeling, and dosing information that the illicit market does not — meaning that restricting the legal market could paradoxically increase harm by driving consumers to untested products.

Researchers who study cannabis policy have noted that the relationship between dispensary availability and adverse outcomes is complex. A WSIPP report published in September 2025 examined the impact of cannabis retail availability on cannabis use and mental health outcomes among Washington Medicaid recipients, though its full findings are still being disseminated through academic channels [27].

Where This Leaves Washington

The UW survey captures a real clinical signal: healthcare providers in a mature legal cannabis market are encountering cannabis-related health problems regularly, and they feel unprepared to address them. The specific conditions they report — psychosis, cannabis hyperemesis syndrome, cannabis use disorder, anxiety — are consistent with the peer-reviewed literature on cannabis risks, particularly for high-potency products and vulnerable populations.

But the survey also reveals that the clinical workforce lacks the training and infrastructure to distinguish signal from noise. When two-thirds of clinicians acknowledge minimal knowledge of cannabis pharmacology, their concern — however genuine — cannot be taken as a reliable proxy for the magnitude of the problem.

The policy path forward likely runs through education and infrastructure rather than prohibition. Potency-based taxation has theoretical appeal but faces political headwinds in a state dependent on cannabis revenue. Standardized clinical screening protocols, expanded referral networks, and integrating cannabis pharmacology into medical education would address the gaps the clinicians themselves identified — and would do so without the unintended consequences of market restriction.

Washington legalized cannabis in 2012 with the promise that regulation would be safer than prohibition. Fourteen years later, the state's clinicians are saying the regulatory framework hasn't given them what they need. Whether the legislature listens may depend less on the science than on whether $500 million in annual tax revenue can coexist with meaningful public health reform.