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Opinion: Screening for Cannabis Misuse in Mental Health Care Must Increase
By Jerrold Pollak, PhD, ABN, ABPP

The evidence for the pernicious long-term neuropsychiatric effects of cannabis use continues to accumulate and has become increasingly difficult to dispute or ignore. This includes a significantly elevated risk for the development of a wide range of relatively early-onset neuropsychiatric conditions accompanied by more pronounced and difficult-to-treat symptoms, as well as the exacerbation of symptoms of established neuropsychiatric illness. Cannabis use has also been implicated in triggering the recurrence of remitted neuropsychiatric difficulties and symptoms (Hasan et al., 2020; Levine et al., 2017; Lowe et al., 2019; Mathai, 2017).

The risk for these adverse consequences is highly associated with onset of use beginning in early adolescence together with persistent and dose-dependent heavy exposure through the young adult years (Pollak, 2016). Recent trends which involve easier access to more potent and potentially destabilizing cannabis are also considered contributory to high rates of impairing neuropsychiatric difficulties through the young adult years (Levine at al., 2017).

Making matters worse, cannabis is the most commonly misused substance associated with problematic and enduring mental status change. More specifically, this includes high rates of consumption among adolescents and young adults—age groups with a heightened vulnerability to the development of serious neuropsychiatric illnesses, notably schizophrenia and related psychotic conditions (Levine at al., 2017; Mathai, 2017).

Cannabis use is also one of the most frequently occurring comorbidities seen in patients with neuropsychiatric illness of varied type which serve to interfere with treatment of the primary neuropsychiatric condition (Lowe et al., 2019).

High rates of consumption have been fueled by changing societal attitudes and beliefs, in particular that cannabis is essentially a harmless substance. This view is used for justification of cannabis’s legalization for recreational and medicinal use despite substantial evidence to the contrary (Lowe et al., 2019). For example, studies have found that about 1 in 3 regular consumers of cannabis develop problematic and chronic use. This can lead to persistent patterns of dependence and withdrawal, elevated rates of transition to more widespread drug use, an amotivational syndrome, or neuro-cognitive impairment (Levine et al., 2017; Mathai, 2017).

Regarding medicinal use, a recent systematic review and meta-analysis of outcome studies failed to show any clear positive impact on mental health conditions while raising concern about exacerbation of neuropsychiatric symptomatology (Black et al., 2019). Moreover, the use of cannabis for the treatment of mental health conditions has not been approved by the FDA (Joshi, 2020).

Impact on Mental Health Care
Problematic cannabis use negatively impacts all aspects of mental health care and is a formidable barrier to achieving reasonably favorable treatment outcomes. Yet it is significantly underrecognized and undertreated. When identified, the extent of cannabis consumption is often minimized by the client and sometimes underestimated by clinicians, especially with regard to its ability to undermine the treatment process.

Formal Screening
No generally accepted consensus guidelines or a standard of care for clinical assessment exists despite the high rates of concerning cannabis use in outpatient mental health care settings, the wide-ranging adverse repercussions of consumption on the treatment process, and the availability of psychometrically sound, brief, easy-to-administer, easily scored, and simple-to-interpret screening instruments used to clarify clinical status (Annaheim & Legleye, 2017; Piontek et al., 2008).

Screening level assessment during the intake assessment and, when indicated, periodic screening over the course of treatment is far more the exception than the rule in most outpatient clinical settings, even in community mental health centers that treat substantial numbers of adolescents and young adults.

How much longer will clients, families, social workers, and other mental health clinicians continue to be shortchanged by this situation? The time is well overdue to undertake formal cannabis use screening with well-established instruments during the mental health intake evaluation process, especially with adolescents and young adults.

Because where there is smoke there is often fire, it would be prudent for social workers to include inquiries about more wide-ranging substance misuse during the intake process, especially when clients formally screen positive for significant cannabis use. As deemed appropriate on a case-by-case basis, formal screening for cannabis use can be repeated periodically over the course of an episode of care.

Referral for a substance abuse consultation should be strongly considered based on findings of problematic consumption or evidence of more widespread substance misuse.

— Jerrold Pollak, PhD, ABN, ABPP, is a clinical and neuropsychologist in the emergency services department at Seacoast Mental Health Center in Portsmouth, NH, and an allied health professional for the department of medical services in the section of psychiatry at Exeter Hospital in Exeter, NH.


Annaheim, B., & Legleye, S. (2017). Short instruments to screen for “problematic” cannabis use in general population surveys. In V.R. Preedy (Ed.), Handbook of cannabis and related pathologies: Biology, pharmacology, diagnosis and treatment (pp. e168-e184). Elsevier.

Black, N., Stockings, E., Campbell, G., Tran, L. T., Zagic, D., Hall, W. D., et al. (2019). Cannabinoids for the treatment of mental disorders and symptoms of mental disorders: A systematic review and meta-analysis. The Lancet-Psychiatry, 6(12), 995-1010.

Hasan, A., von Keller, R., Friemel, C. M., Hall, W. Schneider, M., Koethe D., et al. (2020). Cannabis use and psychosis: A review of reviews. European Archives of Psychiatry and Clinical Neuroscience, 270(4), 403-412.

Joshi, K. G. (2020). Cannabis-derived compounds: What you need to know. Current Psychiatry, 19(10), 64-65.

Levine, A., Clemenza, K., Rynn, M., & Lieberman, J. (2017). Evidence for the risks and consequences of adolescent cannabis exposure. Journal of the Academy of Child and Adolescent Psychiatry, 56(3), 214-225.

Lowe, D. J. E., Sasiadek, J. D., Coles, A. S., & George, T. P. (2019). Cannabis and mental illness: A review. European Archives of Psychiatry and Clinical Neuroscience, 269(1), 107-120.

Mathai, D. S. (2017). Persistent and long-term neuropsychiatric implications of cannabis use in adolescents. American Journal of Psychiatry Residents’ Journal, 12(6), 8-10.

Piontek, D., Kraus, L., & Klempova, D. (2008). Short scales to assess cannabis-related problems. A review of psychometric properties. Substance Abuse Treatment, Prevention and Policy, 3, 25.

Pollak, J. (2016). Cannabis Use — Neuropsychiatric effects of early onset (adolescent use). Paradigm, 20, 12-13, 20.