Poorer Mental Health Linked to Cannabis Use Among Cancer Survivors, Study Finds

A cancer diagnosis changes nearly everything about how a person thinks about their body, their future, and the tools they are willing to try to feel better. Among those tools, few have risen as quickly in public interest as cannabis. Now a large survey-based study from a National Cancer Institute-designated comprehensive cancer center in Southern California suggests that the survivors turning to cannabis after their diagnosis are, in large part, those who feel worse, not better. The research, published in Supportive Care in Cancer, found that cancer survivors who rated their mental health as average or below average had nearly twice the odds of using cannabis after their diagnosis compared with survivors who described their mental health as very good or excellent.

The study was led by researchers at San Diego State University and UC San Diego Health Moores Cancer Center, who surveyed people who had received care at the cancer center between January 2018 and December 2019. Of 5,901 eligible individuals invited to complete an online survey in 2022, 954 responded, and after exclusions for missing data and stage 0 diagnoses, 652 respondents formed the analytic sample. Crucially, the team weighted these responses to reflect the demographics of the full cancer center patient population, producing a weighted sample of 4,620 survivors. The weighted population was 58.6 percent non-Hispanic White, 58.5 percent female, and more than half were aged 65 or older, with breast cancer and genitourinary cancers the most common diagnoses.

The methodological core of the study is straightforward but carefully executed. Participants answered a single question about whether they had used cannabis at any time since their cancer diagnosis, with use defined broadly to include THC-containing and CBD-containing products such as marijuana, concentrates, CBD-only products, prescription cannabinoids, edibles, and topical preparations. The researchers then examined three self-rated exposures: physical health, mental health, and overall quality of life, each captured on a scale from poor to excellent and dichotomized into above average versus average or below average. Because the three measures were moderately to strongly correlated, each was modeled separately using survey-weighted multivariable logistic regression, adjusted for age, sex at birth, race and ethnicity, cancer type, cancer stage, treatment status, and pre-diagnosis cannabis use.

The headline result concerns mental health. Survivors who rated their mental health as average or below average had significantly higher odds of post-diagnosis cannabis use, with an adjusted odds ratio of 1.88 and a 95 percent confidence interval of 1.13 to 3.11. In other words, after accounting for demographic and clinical differences, struggling mentally was associated with roughly an 88 percent increase in the odds of having used cannabis since diagnosis. The associations pointed in the same direction for the other two health domains but did not reach statistical significance: average or below average physical health yielded an odds ratio of 1.38, and average or below average quality of life an odds ratio of 1.24, both with confidence intervals crossing one.

The researchers also probed whether these relationships changed depending on clinical context, stratifying by cancer stage at diagnosis, treatment status, and whether the survivor had used cannabis before cancer. None of the formal interaction tests reached significance, meaning the team cannot claim the associations truly differ across these subgroups. Still, the stratified analyses were striking. Among survivors diagnosed with non-advanced disease, stages I or II, poorer mental health was associated with more than double the odds of cannabis use. The same held for survivors who had completed treatment, with an odds ratio of 2.01. Most eye-opening was the finding among people who had never used cannabis before their cancer diagnosis: those with average or below average mental health had more than four times the odds of starting cannabis afterward.

That last result raises an intriguing possibility that the authors address directly. A cancer diagnosis may serve as an initiation point for cannabis use among some survivors who had never previously touched the drug, potentially driven by a search for symptom relief. The authors caution, however, that this estimate was imprecise and could reflect other explanations, including how lifetime pre-diagnosis use was measured, whether some former users quit before diagnosis, simple reporting error, or residual confounding by factors the survey did not capture. Even with those caveats, the pattern fits a broader picture in which cannabis functions less as a wellness upgrade and more as a coping mechanism for distress.

The numbers behind who is using cannabis are themselves notable. In the weighted sample, 51.9 percent of survivors reported using cannabis before their cancer diagnosis, 32.0 percent reported using it after diagnosis, and another 14.6 percent said they had considered using it. Meanwhile, two-thirds of survivors rated their mental health and quality of life as above average, while only 47.1 percent said the same of their physical health. These figures sit within a larger American context: an estimated 18.6 million cancer survivors were living in the United States as of 2025, and cannabis use has grown steadily among adults with chronic health conditions as legalization has spread and perceptions of safety have softened.

There is an uncomfortable gap between enthusiasm and evidence. In previous work by the same team, more than 80 percent of surveyed survivors perceived benefits from cannabis, most commonly pain relief, reduced stress, anxiety, or depression, and better management of treatment-related side effects. Yet clinical guidelines tell a more reserved story. The American Society of Clinical Oncology’s guideline on cannabis and cannabinoids in adult cancer care concluded that the evidence is insufficient to recommend for or against cannabis for most cancer-related symptoms. The new study adds a useful observational data point: whatever survivors hope cannabis will do, those drawn to it are disproportionately those reporting mental distress, which may signal unmet symptom needs rather than proven therapeutic benefit.

The authors frame their findings through established behavioral science frameworks, including Symptom Management Theory and the Self-Medication Hypothesis. The former emphasizes that patients’ behavior is organized around the experience of symptoms and the pursuit of relief, while the latter proposes that people use substances to cope with persistent physical or psychological distress. Both fit the data: mental health emerged as the health domain most consistently tied to cannabis use, and the researchers suggest it may represent a target for clinical intervention, particularly because oncology clinicians may not know whether their patients are using cannabis at all. The pattern also aligns with the team’s earlier finding that survivors who perceived any of fifteen listed cannabis benefits had more than five-fold higher odds of use, while perceiving any risks cut the odds by 59 percent.

The study’s limitations deserve honest weight. Because the design is cross-sectional, cannabis use and self-rated health were measured at the same moment, so the direction of the relationship cannot be established and may well run in both directions. Cannabis use was self-reported and not verified through medical records or biological testing, and THC and CBD were lumped together despite being pharmacologically distinct compounds, obscuring any differential effects. Response rates were modest, selection bias is possible, and the single-institution setting in a state with legal medical and recreational cannabis may limit generalizability to regions with different laws. Still, the weighted sampling, the large clinical population, and the separation of physical health, mental health, and quality of life into distinct domains represent genuine advances over earlier work that treated quality of life as a single composite. The authors call for longitudinal studies to clarify timing, qualitative work to capture how survivors view cannabis within their coping strategies, and finer-grained measurement of products, frequency, and route of administration. As cannabis becomes ever more embedded in cancer culture, the question is shifting from whether survivors use it to why some do, some do not, and what their choices reveal about the gaps in supportive cancer care.

Subject of Research: Post-diagnosis cannabis use and its association with self-rated health status and quality of life among cancer survivors

Article Title: Post-diagnosis cannabis use and its association with health status and quality of life in cancer survivors

Article References: Kasiri, N., McDaniels-Davidson, C., Doran, N., Patel, S. P., Strong, D. R., & Parada, H., Jr (2026). Post-diagnosis cannabis use and its association with health status and quality of life in cancer survivors. Supportive Care in Cancer, 34(10), Article 931. https://doi.org/10.1007/s00520-026-11185-w

Image Credits: AI Generated

DOI: 10.1007/s00520-026-11185-w

Keywords: cannabis, cancer survivors, mental health, quality of life, physical health, THC, CBD, survivorship care, self-rated health, Supportive Care in Cancer, medical cannabis, logistic regression